U.S. patent application number 14/955584 was filed with the patent office on 2016-03-24 for b-side feed for critical power applications.
The applicant listed for this patent is BLOOM ENERGY CORPORATION. Invention is credited to Arne Ballantine, Ranganathan Gurunathan, Chad Pearson, Muralidhara Ramakrishna Shyamavadhani, KR Sridhar, William Thayer.
Application Number | 20160087443 14/955584 |
Document ID | / |
Family ID | 47361173 |
Filed Date | 2016-03-24 |
United States Patent
Application |
20160087443 |
Kind Code |
A1 |
Ballantine; Arne ; et
al. |
March 24, 2016 |
B-SIDE FEED FOR CRITICAL POWER APPLICATIONS
Abstract
A method of providing power to a load, such as an IT load,
includes generating an output power using at least one power module
comprising at least one fuel cell segment, providing a first
portion of the output power through a grid to an A-side power feed
of the load, and providing a second portion of the output power to
a B-side power feed of the load.
Inventors: |
Ballantine; Arne; (Palo
Alto, CA) ; Gurunathan; Ranganathan; (Bangalore,
IN) ; Shyamavadhani; Muralidhara Ramakrishna;
(Bangalore, IN) ; Pearson; Chad; (Mountain View,
CA) ; Thayer; William; (Los Gatos, CA) ;
Sridhar; KR; (Los Gatos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BLOOM ENERGY CORPORATION |
Sunnyvale |
CA |
US |
|
|
Family ID: |
47361173 |
Appl. No.: |
14/955584 |
Filed: |
December 1, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13533496 |
Jun 26, 2012 |
9214812 |
|
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14955584 |
|
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|
61501382 |
Jun 27, 2011 |
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Current U.S.
Class: |
307/82 |
Current CPC
Class: |
H02J 3/386 20130101;
Y02E 10/76 20130101; H02J 9/06 20130101; H02J 3/387 20130101; Y02B
90/10 20130101; Y02E 10/56 20130101; H02J 3/0073 20200101; H02J
3/383 20130101; H02J 3/382 20130101 |
International
Class: |
H02J 3/38 20060101
H02J003/38 |
Claims
1. A power generation system, comprising: at least one power module
comprising at least one fuel cell segment configured to generate an
output power; at least one first output module comprising at least
one power conditioning component electrically coupled between the
at least one power module and a grid; a first bus electrically
connecting the grid to an A-side power feed of a load, such that
the at least one power module is configured to supply power to the
A-side power feed of the load through the at least one first output
module; at least one second output module comprising at least one
power conditioning component electrically coupled between the at
least one power module and a B-side power feed of the load; wherein
the load comprises a dual corded power supply having two sets of
power electronics that may draw power from at least one of the
A-side feed and the B-side feed in an auctioneering fashion.
2. A method of providing power to a load, comprising: generating an
output power using at least one power module comprising at least
one fuel cell segment; providing a first portion of the output
power through a grid to an A-side power feed of the load; and
providing a second portion of the output power to a B-side power
feed of the load; wherein substantially no power spike is
experienced by the load when the grid experiences a power outage.
Description
BACKGROUND
[0001] Electrical power systems can be used to provide electrical
power to one more loads such as buildings, appliances, lights,
tools, air conditioners, heating units, factory equipment and
machinery, power storage units, computers, security systems, etc.
The electricity used to power loads is often received from an
electrical grid. However, the electricity for loads may also be
provided through alternative power sources such as fuel cells,
solar arrays, wind turbines, thermo-electric devices, batteries,
etc. The alternative power sources can be used in conjunction with
the electrical grid, and a plurality of alternative power sources
may be combined in a single electrical power system. Alternative
power sources are generally combined after conversion of their DC
output into an alternating current (AC). As a result,
synchronization of alternative power sources is required.
[0002] In addition, many alternative power sources use machines
such as pumps and blowers which run off auxiliary power. Motors for
these pumps and blowers are typically 3-phase AC motors which may
require speed control. If the alternative power source generates a
direct current (DC), the direct current undergoes several states of
power conversion prior to delivery to the motor(s). Alternatively,
the power to the motors for pumps, blowers, etc. may be provided
using the electrical grid, an inverter, and a variable frequency
drive. In such a configuration, two stages of power conversion of
the inverter are incurred along with two additional stages of power
conversion for driving components of the AC driven variable
frequency drive. In general, each power conversion stage that is
performed adds cost to the system, adds complexity to the system,
and lowers the efficiency of the system.
[0003] Operating individual distributed generators such as fuel
cell generators both with and without a grid reference and in
parallel with each other without a grid reference is problematic in
that switch-over from current source to voltage source must be
accommodated. Additionally, parallel control of many grid
independent generators can be problematic.
[0004] To address the mode mode-switch-over issue, a
double-inverter arrangement may be utilized. This allows one
inverter to be used in grid tie and a second inverter to be used
with the stand-alone load. An exemplary double-inverter arrangement
with a load dedicated inverter that is located internally in an
input/output module of a solid oxide fuel cell (SOFC) system is
described in U.S. patent application Ser. No. 12/148,488 (filed May
2, 2008 and entitled "Uninterruptible Fuel Cell System"), the
disclosure of which is incorporated herein by reference in its
entirety for all purposes.
[0005] Another approach is to drop power for 5-10 cycles to switch
modes. If a single inverter is used, a time of 5-10 cycles would be
required to drop grid tie and establish voltage mode control.
[0006] Yet another approach is to use frequency droop to control
the amount of power sharing in grid tied export or in load stand
alone output control.
SUMMARY
[0007] Embodiments include a power generation system, comprising at
least one power module comprising at least one fuel cell segment
configured to generate an output power, at least one first output
module comprising at least one power conditioning component
electrically coupled between the at least one power module and a
grid, a first bus electrically connecting the grid to an A-side
power feed of a load, such that the at least one power module is
configured to supply power to the A-side power feed of the load
through the at least one first output module, and at least one
second output module comprising at least one power conditioning
component electrically coupled between the at least one power
module and a B-side power feed of the load.
[0008] Further embodiments include a power generation system,
comprising at least one power module comprising at least one fuel
cell segment generating an output power, at least one
uninterruptible power module comprising at least one DC/AC inverter
and at least one DC/DC converter which is electrically coupled
between the at least one power module and a direct DC power feed to
a load, a DC input bus electrically connecting the at least one
power module and the at least one uninterruptible power module, and
a DC output bus electrically connecting the at least one
uninterruptible power module and a load. At least a portion of the
output power generated by the at least one power module is provided
over the DC input bus at a first voltage to the at least one
uninterruptible power module, and is provided from the at least one
uninterruptable power module over the DC output bus at a second
voltage, different than the first voltage, to the load.
[0009] Further embodiments include a method of providing power to a
load, comprising generating an output power using at least one
power module comprising at least one fuel cell segment, providing a
first portion of the output power through a grid to an A-side power
feed of the load, and providing a second portion of the output
power to a B-side power feed of the load.
[0010] Still further embodiments include a method of providing
power to a load including generating an output power using at least
one power module comprising at least one fuel cell segment,
providing a first portion of the output power to a grid, providing
a second portion of the output power to a DC/DC converter that
converts the output power from a first voltage to a second voltage,
and providing the output power at the second voltage to the
load.
DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1A is a block diagram illustrating a system according
to an embodiment.
[0012] FIGS. 1B to 1K illustrate the system of FIG. 1A in various
modes of operation.
[0013] FIGS. 2 and 3 are block diagrams illustrating a DC microgrid
according to an embodiment.
[0014] FIG. 4 is a block diagram illustrating an IOM comprising an
inverter that is configured for "bi-directional" operation
according to an embodiment.
[0015] FIG. 5 is a block diagram illustrating an IOM comprising an
inverter that is configured for dual mode functionality according
to an embodiment.
[0016] FIGS. 6A-6E illustrate various modes of operation of the
system of the type shown in FIG. 1A. to provide power to an
electric vehicle (EV) charging station according to
embodiments.
[0017] FIG. 7A-B are block diagrams illustrating embodiment systems
for powering a data center load having "A" and "B" side feeds.
[0018] FIG. 8 is a block diagram illustrating an embodiment system
for providing power to a medical facility.
[0019] FIG. 9 is a block diagram illustrating a further embodiment
system for providing power to a medical facility.
[0020] FIGS. 10A-B are block diagrams illustrating embodiment
systems for providing a DC power feed to an AC load.
[0021] FIG. 11 is a block diagram illustrating an embodiment system
for providing power to a load using distributed generator power
modules and microturbines.
DETAILED DESCRIPTION
[0022] Referring to FIG. 1, a fuel cell system according to an
embodiment includes a uninterruptable power module (UPM) 102, an
input/output module (IOM) 104 and one or more power modules 106. If
there is more than one power module 106, for example six to ten
modules 106, then each power module may comprise its own housing.
Each housing may comprise a cabinet or another type of full or
partial enclosure, for example the cabinet described in U.S.
application Ser. No. 12/458,355, filed on Jul. 8, 2009 and
incorporated herein by reference in its entirety. The modules may
be arranged in one or more rows or in other configurations.
[0023] The UPM 102 includes at least one DC/AC inverter 102A. If
desired, an array of inverters may be used. Any suitable inverter
known in the art may be used. The UPM 102 optionally contains an
input rectifier, such as an input diode 102B which connects to the
output of a DC bus 112 from the power module(s) 106 and to the
input of the at least one inverter 102A. The UPM also optionally
contains a boost PFC rectifier 102C which connects to the output of
the electric grid 114, such as a utility grid, and to the input of
the at least one inverter 102A.
[0024] The IOM 104 may comprise one or more power conditioning
components. The power conditioning components may include
components for converting DC power to AC power, such as a DC/AC
inverter 104A (e.g., a DC/AC inverter described in U.S. Pat. No.
7,705,490, incorporated herein by reference in its entirety),
electrical connectors for AC power output to the grid, circuits for
managing electrical transients, a system controller (e.g., a
computer or dedicated control logic device or circuit), etc. The
power conditioning components may be designed to convert DC power
from the fuel cell modules to different AC voltages and
frequencies. Designs for 208V, 60 Hz; 480V, 60 Hz; 415V, 50 Hz and
other common voltages and frequencies may be provided.
[0025] Each power module 106 cabinet is configured to house one or
more hot boxes. Each hot box contains one or more stacks or columns
of fuel cells 106A (generally referred to as "segments"), such as
one or more stacks or columns of solid oxide fuel cells having a
ceramic oxide electrolyte separated by conductive interconnect
plates. Other fuel cell types, such as PEM, molten carbonate,
phosphoric acid, etc. may also be used.
[0026] Fuel cells are often combined into units called "stacks" in
which the fuel cells are electrically connected in series and
separated by electrically conductive interconnects, such as gas
separator plates which function as interconnects. A fuel cell stack
may contain conductive end plates on its ends. A generalization of
a fuel cell stack is the so-called fuel cell segment or column,
which can contain one or more fuel cell stacks connected in series
(e.g., where the end plate of one stack is connected electrically
to an end plate of the next stack). A fuel cell segment or column
may contain electrical leads which output the direct current from
the segment or column to a power conditioning system. A fuel cell
system can include one or more fuel cell columns, each of which may
contain one or more fuel cell stacks, such as solid oxide fuel cell
stacks.
[0027] The fuel cell stacks may be internally manifolded for fuel
and externally manifolded for air, where only the fuel inlet and
exhaust risers extend through openings in the fuel cell layers
and/or in the interconnect plates between the fuel cells, as
described in U.S. Pat. No. 7,713,649, which is incorporated herein
by reference in its entirety. The fuel cells may have a cross flow
(where air and fuel flow roughly perpendicular to each other on
opposite sides of the electrolyte in each fuel cell), counter flow
parallel (where air and fuel flow roughly parallel to each other
but in opposite directions on opposite sides of the electrolyte in
each fuel cell) or co-flow parallel (where air and fuel flow
roughly parallel to each other in the same direction on opposite
sides of the electrolyte in each fuel cell) configuration.
[0028] Power modules may also comprise other generators of direct
current, such as solar cell, wind turbine, geothermal or
hydroelectric power generators.
[0029] The segment(s) 106A of fuel cells may be connected to the DC
bus, 112 such as a split DC bus, by one or more DC/DC converters
106B located in module 106. The DC/DC converters 106B may be
located in the IOM 104 instead of the power module 106.
[0030] The power module(s) 106 may also optionally include an
energy storage device 106C, such as a bank of supercapacitors or
batteries. Device 106C may also be connected to the DC bus 112
using one or more DC/DC converters 106D.
[0031] The UPM 102 is connected to an input/output module (IOM) 104
via the DC bus 112. The DC bus receives power from power modules
106.
[0032] The fuel cell system and the grid 114 are electrically
connected to a load 108 using a control logic unit 110. The load
may comprise any suitable load which uses AC power, such as one or
more buildings, appliances, lights, tools, air conditioners,
heating units, factory equipment and machinery, power storage
units, computers, security systems, etc. The control logic unit
includes a switch 110A and control logic 110B, such as a computer,
a logic circuit or a dedicated controller device. The switch may be
an electrical switch (e.g., a switching circuit) or an
electromechanical switch, such as a relay.
[0033] Control logic 110B routes power to the load 108 either from
the UPM 102 or from the grid 114 using switch 110A. The at least
one fuel cell segment 106A and storage device 106C from module 106
are electrically connected in parallel to the at least one first
inverter 104A in IOM and to the at least one second inverter 102A
in the UPM 102. The at least one first inverter 104A is
electrically connected to the load 108 through the electrical grid
114 using switch 110A in the first position. In contrast to the
circuit shown in U.S. patent application Ser. No. 12/148,488 (filed
May 2, 2008 and entitled "Uninterruptible Fuel Cell System"), the
grid 114 in FIG. 1A is directly connected to the load 108 through
the control logic unit 110 without passing through a bidirectional
inverter. The at least one second inverter 102A is electrically
connected to the load 108 with the switch 110A in the second
position without using the electrical grid 114 (i.e., the output of
the fuel cell segment 106A does not have to pass through the grid
114 to reach the load 108).
[0034] Thus, the control logic 110B selects whether to provide
power to the load from the electrical grid 114 (or from the fuel
cell segment 106A through the grid) or through the at least one
second inverter 102A. The control logic 110B may determine a state
of the power modules and select a source to power the load 108
based on the state of the power modules, as described below.
[0035] A second switch 116 controls the electrical connection
between the IOM 104 and the grid 114. Switch 116 may controlled by
the control logic 110B or by another system controller.
[0036] By way of illustration and not by way of limitation, the
system contains the following electrical paths: [0037] A path to
the load 108 from the AC grid 114. [0038] A path from the AC grid
114 through the IOM 104 to storage elements 106C of power modules
106 (for example, supercapacitors or batteries). [0039] A path from
the storage elements 106C of the power modules 106, over the DC bus
112 to the IOM 104 and the UPM 102 in parallel. The DC bus delivers
DC to the inverter in the UPM 102. The inverter 102A in the UPM 102
or inverter 104A in IOM 104 delivers AC power to the load 108
depending on the position of the switch 110A. [0040] A path from
the power modules 106 (which may include power from the fuel cell
segment(s) 106A and/or the storage elements 106C of the power
modules 106), over the DC bus 112 to the IOM 104 and the UPM 102.
The DC bus delivers DC voltage to the inverter in the UPM 102. The
inverter 102A in the UPM 102 delivers AC power to the load 108.
Power in excess of the power required by the load 108 is delivered
to the AC grid through an inverter 104A in the IOM 104. The amount
of power that is delivered to the AC grid 114 will vary according
the demands of the load 108. If the amount of power required by the
load 108 exceeds the power provided by the power modules 106, the
additional power demand may be supplied by the AC grid 114 directly
to the load 108 through switch 110A in the first position or to the
UPM 102 with the switch 110A in the second position. The grid power
is rectified in rectifier 102C in UPM 102 and provided to the
inverter 102A in the UPM 102 and converted back to AC for powering
the load 108.
[0041] FIGS. 1B-1K illustrate various modes of operation of the
system shown in FIG. 1A. While the embodiments described below
illustrate a load 108 which requires 100 kW of power and the fuel
cell segment(s) 106A which output 200 kW of power in steady state,
these values are provided for illustration only and any other
suitable load and power output values may be used.
[0042] FIG. 1B illustrates the system operation during the
installation of the system and/or during a period when the load 108
receives power from the grid 114. As shown in this figure, the fuel
cell segment(s) 106A and the energy storage device 106C are in the
OFF state, the IOM 104 inverter 104A and the UPM inverter 102A are
both in the OFF state and the second switch 116 is open such that
there is no electrical communication between the IOM and the grid.
The control logic switch 110A is in the first position to provide
power from the grid 114 to the load 108 through the control logic
module 110. As shown in the figure, 100 kW of power is provided
from the grid to the load through the control logic module.
[0043] FIG. 1C illustrates the system operation during IOM start-up
and charging of the energy storage device (e.g., bank of
supercapacitors) 106C from the grid 114 while the load 108 receives
power from the grid 114. As shown in this figure, the fuel cell
segment(s) 106A are in the OFF state while the energy storage
device 106C is in the ON state. The IOM 104 bi-directional inverter
104A is in the ON state and the UPM inverter 102A is in the OFF
state. The second switch 116 is closed such that there is
electrical communication between the IOM and the grid to provide
power from the grid 114 to the energy storage device 106C through
the IOM 104 inverter 104A and the DC bus 112. The control logic
switch 110A is in the first position to provide power from the grid
114 to the load 108 through the control logic module 110. As shown
in the figure, 100 kW of power is provided from the grid to the
load through the control logic module.
[0044] FIG. 1D illustrates the system operation during UPM start-up
following IOM start-up. UPM functions by receiving power from the
energy storage device 106C. UPM provides the power from the energy
storage device 106C to the load 108. As shown in this figure, the
fuel cell segment(s) 106A are in the OFF state while and the energy
storage device 106C is in the ON state. The IOM 104 bi-directional
inverter 104A is in the ON state and the UPM inverter 102A is in
the ON state. The second switch 116 is closed such that there is
electrical communication between the IOM and the grid. The control
logic switch 110A is in the second position to provide power from
the UPM 102 to the load 108 through the control logic module 110.
As shown in the figure, 100 kW of power is provided from the grid
114 to the load 108 through the rectifier 102C and inverter 102A of
the UPM 102 and then through the control logic module. Some power
may also be provided to the load 108 from the energy storage device
106C via the DC bus 112, UPM 102 and control logic module.
[0045] FIG. 1E illustrates the steady state operation of the
system. In this mode the fuel cell segment(s) 106A is in the ON
state to power the load 108. The segment(s) 106A may provide 200 kW
of power in a steady state mode (this may be the designed power
output or a maximum power output). As shown in this figure, the
energy storage device 106C is in the ON state to act as an
emergency backup power source. The IOM 104 bi-directional inverter
104A is in the ON state and the UPM inverter 102A is in the ON
state. The 200 kW power output is split between the grid 114 and
the load 108. The second switch 116 is closed such that there is
electrical communication between the IOM and the grid to provide
100 kW of power from the fuel cell segment(s) 106A to the grid. The
control logic switch 110A is in the second position to provide the
other 100 kW of power from the fuel cell segment(s) 106A in the
power module 106 through the DC bus passing through IOM 104 and
through the inverter 102A of the UPM 102 and then through the
control logic module 110 to the load 108. Preferably, this 100 kW
of power does not pass through the IOM inverter 104A and/or the
grid 114 to reach the load 108. While a 200 kW power output split
50/50 between the grid and the load is described above, different
power outputs may be used as needed, such as 25 kW to 1000 kW,
which may be split 10/90 to 90/10 between the grid and the
load.
[0046] FIG. 1F illustrates operation of the system during a
relatively steady load 108 increase from 100 kW to 150 kW (i.e.,
when the load requires more power than prior steady state
operation). In this mode, more of the power output of the fuel cell
segment(s) is provided to the load and less of this power output is
provided to the grid than in the steady state mode described above.
If desired, 100% of the power output may be provided to the load
and 0% to the grid. The fuel cell segment(s) 106A is in the ON
state to power the load 108. As shown in this figure, the energy
storage device 106C is in the ON state to act as an emergency
backup power source. The IOM 104 bi-directional inverter 104A is in
the ON state and the UPM inverter 102A is in the ON state. The
second switch 116 is closed such that there is electrical
communication between the IOM and the grid to provide 50 kW of
power from the fuel cell segment(s) 106A through the IOM inverter
104A to the grid 114. The control logic switch 110A is in the
second position to provide 150 kW of power from the fuel cell
segment(s) 106A in the power module 106 through the DC bus passing
through IOM 104 and through the inverter 102A of the UPM 102 and
then through the control logic module 110 to the load 108. Thus,
the power output of the fuel cell segment(s) 106A is preferably
split between the grid and the load in this mode. Preferably, the
power does not pass through the IOM inverter 104A and/or the grid
114 to reach the load 108.
[0047] FIG. 1G illustrates operation of the system during a sudden
load 108 spike which requires more power than the fuel cell
segment(s) 106A can generate at that time. For example, the load
spike is from 100 kW to 225 kW while the segment(s) 106A can only
generate 200 kW of power in steady state or in maximum power mode.
The fuel cell segment(s) 106A is in the ON state to power the load
108. As shown in this figure, the energy storage device 106C is in
the ON state to act as an emergency backup power source. The IOM
104 bi-directional inverter 104A is in the ON state and the UPM
inverter 102A is in the ON state. The second switch 116 is closed
such that there is electrical communication between the IOM and the
grid. However, no power is provided from fuel cell segment(s) 106A
through the IOM inverter 104A to the grid 114 due to the load
spike. The control logic switch 110A is in the second position to
provide power from the fuel cell segment(s) 106A in the power
module 106 and from the grid 114 through the DC bus passing through
IOM 104 and through the inverter 102A of the UPM 102 and then
through the control logic module 110 to the load 108. In this mode,
the power to the load is provided from both the fuel cell
segment(s) and the grid. As shown, 200 kW from the segment(s) 106A
is provided through the DC bus 112, diode 102B, inverter 102A and
switch 110A to the load 108, while 25 kW is provided from the grid
114 through the rectifier 102B, inverter 102A and switch 110A to
the load 108 to achieve a total 225 kW of power required by the
load. Preferably, the power from the fuel cell segment(s) does not
pass through the IOM inverter 104A and/or the grid 114 to reach the
load 108.
[0048] FIG. 1H illustrates operation of the system during a return
to normal or steady state operation after the sudden load 108
spike. The fuel cell segment(s) 106A is in the ON state to power
the load 108. As shown in this figure, the energy storage device
106C is in the ON state to act as an emergency backup power source.
The IOM 104 bi-directional inverter 104A is in the ON state and the
UPM inverter 102A is in the ON state. The second switch 116 is
closed such that there is electrical communication between the IOM
and the grid. The control logic switch 110A is in the second
position to provide power from the fuel cell segment(s) 106A in the
power module 106 through the DC bus passing through IOM 104 and
through the inverter 102A of the UPM 102 and then through the
control logic module 110 to the load 108. In this mode, the fuel
cell segment(s) continue to output steady state or maximum power
(e.g., 200kW) which is split between the load and the grid. As
shown, 200 kW from the segment(s) 106A is provided to the IOM 104.
IOM 104 provides 100 kW of power from fuel cell segment(s) 106A
through the IOM inverter 104A to the grid 114. The DC bus 112
provides the remaining 100 kW of power from IOM 104 through diode
102B, inverter 102A and switch 110A to the load 108. Preferably,
the power does not pass through the IOM inverter 104A and/or the
grid 114 to reach the load 108.
[0049] FIG. 1I illustrates operation of the system during loss of
power from the grid 114 (e.g., during a black out). The fuel cell
segment(s) 106A is in the ON state to power the load 108. As shown
in this figure, the energy storage device 106C is in the ON state
to absorb power from the fuel cell segment(s) 106A and to the
soften the "step" that occurs during the loss of the grid power.
The IOM 104 bi-directional inverter 104A is in the ON state and the
UPM inverter 102A is in the ON state. The second switch 116 is
opened such that there is no electrical communication between the
IOM and the grid. A sensor can sense the loss of grid power and a
controller can open the switch 116 in response to the sensed grid
outage. The control logic switch 110A is in the second position to
provide power from the fuel cell segment(s) 106A in the power
module 106 through the DC bus passing through IOM 104 and through
the inverter 102A of the UPM 102 and then through the control logic
module 110 to the load 108. In this mode, out of the 200 kW total
power output from the segment(s) 106A, 100 kW is provided to the DC
bus 112 and 100 kW is provided to the energy storage device 106C to
soften the step. The DC bus 112 provides the 100 kW of power from
IOM 104 through diode 102B, inverter 102A and switch 110A to the
load 108. The power output of the segment(s) 106A is then gradually
reduced to 100 kW to meet the requirements of the load 108.
[0050] FIG. 1J illustrates operation of the system during loss of
power from the grid 114 (e.g., during a black out) and in case of a
load transient (e.g., increased demand for power from load 108)
while the fuel cell segment(s) output a reduced amount of power
(e.g., 100 kW) which meets the steady state requirements of the
load. The fuel cell segment(s) 106A is in the ON state to power the
load 108. As shown in this figure, the energy storage device 106C
is in the ON state to provide additional power to the load 108. The
IOM 104 bi-directional inverter 104A is in the ON state and the UPM
inverter 102A is in the ON state. The second switch 116 is opened
such that there is no electrical communication between the IOM and
the grid. The control logic switch 110A is in the second position
to provide power from the fuel cell segment(s) 106A and the energy
storage device 106C in the power module 106 through the DC bus
passing through IOM 104 and through the inverter 102A of the UPM
102 and then through the control logic module 110 to the load 108.
In this mode, 100 kW from the segment(s) 106A and 50 kW from the
energy storage device is provided to the DC bus 112. Thus, the DC
bus 112 provides the 150 kW of power from IOM 104 through diode
102B, inverter 102A and switch 110A to the load 108. Preferably,
the power does not pass through the IOM inverter 104A and/or the
grid 114 to reach the load 108.
[0051] FIG. 1K illustrates operation of the system during loss of
power from the grid 114 (e.g., during a black out) and in case of a
continuing load transient (e.g., continued increased demand for
power from load 108). The operation is the same as that shown in
FIG. 1J, except that the power output of the energy storage device
106C is ramped down to zero over time and the power output of the
fuel cell segment(s) is ramped up to the power needed by the load
(e.g., 150 kW) over the same time. Thus, over time, the load
receives more and more power from the fuel cell segment(s) 106A and
less and less power from the energy storage device 106C until all
of the required power is supplied to the load 108 by the fuel cell
segment(s). Thus, the energy storage device acts as a bridging
power source during the initial load transient and is then phased
out during the continuing load transient.
[0052] Referring to FIGS. 2 and 3, the output of the DC sources 1
to N are paralleled at the DC-output point, and a DC bus is
created. Each DC source 1 to N may comprise one or more power
module(s) 106 and an associated IOM 104. The 1 to N sources feed
the customer load via a single UPM. Thus, the plurality of power
module/IOM pairs share a common UPM. For example, the DC bus may
form a DC micro grid connecting any number of DC sources (e.g.,
SOFC and power conditioning systems) together at one UPM. The UPM
202 may be a large assembly of individual UPM's 102 shown in FIG.
1A capable of output of many multiples of the output of the SOFC
systems themselves. As illustrated, in FIG. 2, the UPM 202
comprises "N" UPMs 102 (i.e., one UPM for each DC source), with a
separate DC bus connecting each DC power source to a dedicated UPM
102. The N UPM's 102 may be arranged in close proximity (e.g., side
by side) in one housing or in separate housings to form the UPM
assembly 202.
[0053] In an alternative embodiment shown in FIG. 3, the assembly
202 of smaller dedicated UPM's 102 may be replaced by one large UPM
302. In this embodiment, the UPM 302 may include an electrical
storage device (e.g., bank of batteries or supercapacitors) and/or
a synchronous motor. In general, UPM inverters may include rotating
machinery (e.g., a motor, flywheel, etc.) to enhance stored energy
content and/or increase reliability and inertia of output.
[0054] In summary, the DC sources may comprise fuel cell power
modules and an IOM. The inverter within each UPM may be a modular
assembly of smaller inverters controlled as one large inverter
acting with inputs and/or outputs in parallel. An inverter within
the main IOM may be a modular assembly of smaller inverters which
are controlled as one large inverter acting with inputs and/or
outputs in parallel.
[0055] In an embodiment, rectification is provided in the UPM to
allow feed from the grid when the stacks are off-line, thus
providing the load a protected bus. A boost converter may be used
to maintain a good power factor to the grid.
[0056] In another embodiment, power from stored energy within an
SOFC system or the UPM is used to create a "UPS" unit which has
three energy inputs: grid energy; SOFC segment energy; and stored
energy (e.g., ultracapacitors or batteries).
[0057] In yet another embodiment, a DC micro-grid is connected to
other distributed generators such as solar power hardware or wind
power hardware.
[0058] In an embodiment, the DC micro-grid is connected to DC loads
such as the loads of DC data centers or DC vehicle chargers.
[0059] In yet another embodiment, when an IOM and UPM are composed
of a cluster of inverters acting in parallel, some or all these
inverters may be de-energized depending upon customer load
conditions. For example, in a 200 kW generation capacity scenario
where the customer load is 150 kW, the IOM inverters may be
de-energized such that they only support 50 kW instead of a full
200 kW of grid-tied output. Further, in this scenario, it may be
that only a portion of the possible inverters in the IOM assembly
may be installed into the IOM, thus providing cost savings in terms
of equipment required to support the specific customer load
scenario.
[0060] Referring to FIG. 4, in an embodiment, an IOM 404 comprises
inverters 412 that are configured for "bi-directional" operation.
Such an inverter may have four-quadrant operation. If the grid-tied
inverter has "bi-directional" operation, then the rectified feed
does not need to be supplied to the UPM 402. Grid power during
start-up may come through the grid tied inverter 412 instead of via
a rectified input to the UPM 402. This embodiment also provides
power from power module(s) 406 for protection of the customer
load.
[0061] Referring to FIG. 5, in an embodiment, a UPM is not
utilized. In this embodiment, an IOM 504 comprises an inverter 512
that is configured for dual mode functionality. The dual mode
inverter 512 is configured to operate with a grid reference and
also in a stand-alone mode, supporting a customer load without a
grid reference. In this embodiment an output power interruption
would be required in order to switch between power generation in
one mode and another mode.
[0062] FIGS. 6A-6D illustrate various modes of operation of the
system shown in FIG. 1A. in which an electric vehicle (EV) charging
module (ECM) is used instead of or in addition to the UPM 102. In
some modes of operation the ECM may perform the functions of the
UPM.
[0063] The systems of FIGS. 6A-6D offer several advantages when
used in EV charging application. In particular, these systems
remove the need for the grid to supply large peaks of power during
quick charging of a large number of EVs. The systems can also be
used for EV charging in areas where it would be too expensive to
provide grid power, and where it would be more cost effective to
lay a natural gas pipeline.
[0064] Referring to FIG. 6A, an EV charging station comprises one
or more power modules 106, an IOM 104 and an ECM 602. ECM contains
a DC/DC converter 602A instead of the inverter 102A of UPM 102. In
this embodiment, the EV charging station (e.g., ECM 602) has access
to grid power. The EV charging station may feed power
simultaneously to the grid and the EV battery. A quick (e.g., 10-20
minute) charge may be provided from ECM 602 to the EV battery 604
using power from the power module 106. Whenever an EV battery 604
is connected to the charging station (e.g., ECM 602) for a charge,
the power module 106 power is automatically diverted from feeding
the grid into the charging station. The diversion of power from the
grid to the EV battery 604 may be accomplished by the control logic
as illustrated in FIG. 1A and as discussed previously. The grid
power may serve as a backup power for the charging station when the
power modules 106 are unavailable.
[0065] Referring to FIG. 6B, an EV charging station comprises one
or more power modules 106, an IOM 104, a UPM 102, control logic
unit 110 and an ECM 602. In this embodiment, the EV charging
station 602 may also be used to supply a customer load 108 while
feeding grid power and charging an EV battery 604. In this
configuration, the EV charging station feeds the grid and also
provides uninterrupted power to the customer load 108 (such as an
office building). The IOM 104 feeds power to the grid, while the
UPM 102 supplies power to the customer load 108. The ECM 602 acts
as the EV charging station and draws power from the 400V DC bus
112. Thus, the UPM 102 and ECM 602 are connected in parallel to the
DC bus 112. While the customer load 108 is supplied without
interruption, anytime a vehicle drives in to get charged by the ECM
602, a portion of the power being fed to the grid is diverted to
the ECM 602 for the time it takes to charge the EV battery 604.
Again, this configuration overcomes the challenge of drawing high
peak power from the grid, which is a major issue today especially
during day time, when the grid is already supplying full
capacity.
[0066] A typical application of this configuration would be to
supply power to an office building. The load 108 from the building
(including data centers, lighting etc) can be supplied clean
uninterrupted power from the UPM 102, while power is being fed to
the grid. Charging stations can be installed at the car park of
this building for the employees and visitors of the company. EV
batteries 604 can be charged, and then parked at the car park.
Options for both quick charging (1 C) and trickle charging (0.1 C)
can be provided at the charging stations, based on the time
constraints of the car owner.
[0067] Referring to FIG. 6C an EV charging station comprises one or
more power modules 106, a UPM 102, an ECM 602 and a DG set 608.
This configuration is suitable for use in remote areas where grid
power is not available. In this configuration, the UPM 102 draws
power from the DC bus connected to the power modules 106, and feeds
the customer load 108. This customer load 108 also acts like a base
load to the power modules 106, which allows the system to operate
at a certain minimum efficiency (in the configurations illustrated
in FIGS. 6A and 6B above, the grid provides the minimum base load
for efficient performance). In an embodiment, the power modules 106
and the UPM 102 are rated such that the maximum customer load is
always supplied while the ECM 602 is operational. The diesel
generator ("DG") set 608 is used to start up the power modules
106.
[0068] Referring to FIG. 6D, an EV charging station comprises one
or more power modules 106 and an ECM 602. This configuration of EV
charging stations is suitable for use where there is no grid power
and no customer load is to be supplied. The EV charging station is
needed only to act as a power source for charging the EV battery
604. In this configuration, a battery bank 610 acts as the base
load to the EV charging station. This battery bank 610 may be
charged using normal charging (0.1 C). An operator of an EV in need
of charging the EV battery 604 may obtain a charge from the ECM
602. Alternatively, the operator may exchange a discharged EV
battery 604 for one of the batteries in the battery bank 610. The
DG 608 set is used to start up the power modules 106.
[0069] In an embodiment, the EV charging station is configured to
take advantage of time-of-day pricing and to utilize the storage
capacity of the EV batteries. For example, the cost of weekday
electricity from 11 AM to 9 PM may be several times (e.g., 5 times)
higher than the cost of electricity from 9 PM to 11 AM. In this
embodiment, DC power is returned from the EV batteries to the fuel
cell system to provide power during peak pricing periods and/or to
support shortfalls in the power output from the power modules 106
due to an internal power module 106 fault.
[0070] Referring to FIG. 6E, the fuel cell system comprises one or
more power modules 106, an IOM 104, a UPM 102, a first control
logic unit 110 described above, a switching module 702 containing a
switch 702A and second control logic unit 702B, and an ECM 602. If
desired, the separate logic units 110 and 702B may be physically
combined into a single unit which performs the functions of the
unit 110 described above and functions of unit 702B described
below. In this embodiment, the power modules 106, IOM 104 and UPM
102 may be used to supply power to a customer load 108 (e.g., a
building, such as an office building) while also being able to
provide power to the grid, while the ECM 602 may be used for
charging an EV battery 604 by drawing power from the 400V DC bus
112. Control logic unit 110 performs the functions as previously
described. Control logic unit 702B performs the functions described
below. Thus, the UPM 102 and ECM 602 are connected in parallel to
the DC bus 112.
[0071] In an embodiment, the UPM 102 (e.g., the inverter 102A of
UMP 102) is rated higher than would required to provide power to
load 108 from the power modules 106 alone. The additional power
handling capabilities are used to utilize additional DC power from
EV batteries that are connected to the EV charging station (i.e.,
to ECM 602). The control logic unit 702B switches the switch 702A
to connect the EV batteries 604 to the ECM 602 receive power from
ECM 602, or to DC bus 112 to provide power to the DC bus 112.
[0072] By way of illustration and not by way of limitation, the
fuel cell system contains power module(s) 106 which are capable of
delivering a first value of maximum power (e.g., 200 kW). The UMP
102 is rated to convert DC to AC to provide a second value of
maximum power (e.g., 400 kW AC) which is greater than the first
value. In other words, the inverter 102A is designed to convert
more DC to AC power than the power module(s) are capable of
providing. The UMP 102 uses the additional conversion capacity to
convert DC power (e.g., up to 200 kW DC) from the EV batteries 604
to AC power to provide to the load 108 or to the grid 114.
[0073] Thus, DC power from an electric vehicle battery 604 is
received at an electric vehicle charging module (ECM) 602 during a
period of higher electricity price from the grid, the received
power is provided to the at least one inverter 102A which converts
the received DC power to AC power, and provides the AC power to a
load (e.g., 108 or grid load 114).
[0074] In one embodiment, DC power is provided from the at least
one fuel cell power module 106 to the ECM 602, and then provided
from the ECM to the electric vehicle battery 604 when the cost of
electricity is lower, prior to the step of receiving DC power.
[0075] The combination EV charging station and fuel cell system may
be located at a business having employees that drive electric cars.
Using the time of day pricing set forth above, these employees
would generally park their EVs at the business recharging docks and
connect the EV batteries 604 to the ECM 602 for 8 to 10 hours
during the work day. Typically, all the EV batteries 604 are fully
charged (with the switch 702A connecting batteries 604 to ECM 602)
before the price of power from the grid increases (e.g., by 11 AM)
using the power provided from the ECM 602. Then, after the price of
the grid power increases (e.g., after 11 AM), logic 702B switches
the switch 702A position to connect the EV batteries 604 to the DC
bus 112. The batteries 604 are then used to provide a portion
(e.g., 10-75%, for example 50%) of their stored charge to the DC
bus 112. For example, the EV batteries may receive more charge each
day (or each week etc.) than they provide back to the DC bus. If
desired, the owners of the EVs may not be charged for the net
charge they received or be charged a reduced rate compared to the
rate for charging EV batteries from the grid. The charging station
could then deliver up to 400 kW AC to load 108 in a peak-shaving
load-following manner. All parties would financially benefit
because of the increased price of the mid-day electricity.
[0076] In another embodiment, the electric vehicle battery is
charged at a location other than the ECM 602 during a lower cost
electricity price period prior to the step of receiving DC power
from the ECM 602 during the higher cost of electricity price
period. For example, EVs are charged at a remote location (e.g.,
from the grid at home overnight) using lower cost, night time
electricity. These EVs may then be connected to the ECM 602 in the
morning. After the price of electricity increases mid-day (e.g.,
after 11 AM) the EV batteries 604 deliver a predetermined portion
of their stored charge to the DC bus 112. Thus bus can then deliver
up to 400 kW AC to load 108 in a peak-shaving load-following
manner. The EV owners may be reimbursed for the cost of provided
power (i.e., for the power they stored at their home and delivered
to the bus 112). Here again all parties financially benefit because
of the higher price of mid-day electricity.
[0077] Of course, the times used in the foregoing examples are for
illustrative purposes only. The charging station may be configured
to utilize power from the EV batteries to address the time-of-day
pricing for the region in which the charging station is
located.
[0078] The above described methods and systems can be readily used
with multiple generators in parallel with a large load, while
allowing tight control of frequency and voltage.
[0079] The following embodiments describe providing a power to a DC
or AC load from a first side from distributed fuel cell power
generation system described above, and from a grid (e.g., utility
or campus grid) or distributed generator (e.g., diesel generator)
(DG) from the second side. Each side may be used as the primary or
secondary side.
[0080] FIG. 7A illustrates an embodiment system 700 for powering a
load 108, which may be an information technology (IT) load, such as
a data center IT load (i.e., devices operating in an IT system
which may include one or more of computer(s), server(s), router(s),
rack(s), power supply connections, and other components found in a
data center environment. As described herein, an IT load (i.e.,
devices operating in an IT system which may include one or more of
computer(s), server(s), router(s), rack(s), power supply
connections, and other components found in a data center
environment) and IT system are distinguished from devices, such as
computers, servers, routers, racks, controllers, power supply
connections, and other components used to monitor, manage, and/or
control the operation of DC power generators and DC power
generation systems in that IT loads do not monitor, manage, and/or
control the operation of any DC power generators or DC power
generation systems that provide power to the IT loads
themselves.
[0081] The data center housing the IT load may comprise a rack that
supports the various servers, routers, etc and/or a building
housing the IT load. As shown in FIG. 7A, the data center IT load
108 may be "dual corded" or "multi-corded," meaning the load 108
receives power from multiple power feeds from different sources
(e.g., "A" side feed, "B" side feed, "C" side feed, etc.).
[0082] As shown in FIG. 7A, the load 108 (e.g., data center rack)
may be dual-corded having an "A" side feed and a "B" side feed. The
load 108 may draw power from both feeds (e.g., 50% power from the
"A" side feed, and 50% power from the "B" side feed). A transfer
switch or static switch inside the load 108 may be power seeking
and may maintain power to the load 108 (via one or both feeds)
under all conditions. In some embodiments, the load 108 may include
a dual corded power supply having two sets of AC/DC electronics
inside (i.e., an "A" side power supply and a "B" side power supply)
which may essentially have a diode-"or" at their output, and power
may be drawn from whichever supply is lined up to a viable source.
In this type of arrangement, a switch may not be required. The
transition from one supply to the other, or power sharing in cases
where power is shared between them, may be accomplished using solid
state components. Thus, the load comprises a dual corded power
supply having two sets of power electronics that may draw power
from at least one of the A-side feed and the B-side feed in an
auctioneering fashion.
[0083] The "A" side feed of the load 108 may be connected to a
standard power infrastructure, such as grid 114 power with optional
distributed generator (e.g., diesel generator) (DG) 706 and
uninterruptable power supply (UPS) 708 backups.
[0084] The "B" side feed of load 108 may be connected to one or
more UPMs 102 (e.g., stand alone inverter outputs).
[0085] The system 700 further includes at least one power module
106 and associated IOM 104. The at least one power module 106 may
provide a first portion of its output power (e.g., between 5-95%,
such as about 50% of its output power) to the "B" side feed of the
load 108 via the one or more UPMs 102. This is illustrated
schematically via arrow 704 in FIG. 7A.
[0086] The at least one power module 106 may provide a second
portion of its output power (e.g., between 5-95%, such as about 50%
of its output power) through its associated IOM 104 to the grid
114. The power from the IOM 104 may be provided through the grid
114 to the "A" side feed of the load 108, which as described above,
is connected to the grid 114. This is illustrated schematically by
arrows 702 in FIG. 7A, which show the power being provided from IOM
104 to the grid 114, and then from the grid 114 through the "A"
side feed to the load 108.
[0087] In various embodiments, during normal operation of the
system 700, the at least one power module 106 may output all or
substantially all of the power required by the load 108. A first
portion of the power output (e.g., .about.50%) may be directly fed
to the "B" side feed of the load 108 via UPM 102. A second portion
of the power output (e.g., .about.50%) may be fed to the grid 114
via IOM 104 and returned from the grid 114 to the "A" side feed of
the load 108. Thus, in various embodiments, no net power for the
load 108 is required from the grid 114, which may substantially
reduce costs for powering a load 108, such as components in a data
center rack, since excess power may not need to be purchased from
the operator of grid 114. Further, because of the loaded IOM 104
output and the loaded UPM 102 output from power modules 106, the
fuel cells in the power modules 106 may be heat-soaked to full or
nearly-full load. Therefore, if there is a step in load (e.g., from
50% to 100%) when the "A" (grid) feed is lost, this may be an easy
transition that places very little strain on the fuel cells.
[0088] In the event of a failure or interruption in the power from
the at least one power module 106 (e.g., the load 108 is not
receiving power over the "B" side feed), then 100% of the power
requirement for the load 108 may be drawn from the grid 114 via the
"A" side feed. The resultant spike in grid power demand (e.g., from
.about.50% to 100% of the load 108 power) may be easily absorbed by
the grid 114.
[0089] In the event of a failure or interruption in the power from
the grid 114, then 100% of the power requirement for the load 108
may be drawn from the at least one power module 106. The power from
the at least one power module 106 may be drawn entirely over the
"B" side feed from UPM 102, or may be drawn in part through the UPM
102 to the "B" side feed and in part through the IOM 104 and grid
114 connection to the "A" side feed. In various embodiments, during
normal operation the at least one power module 106 may output at
least about 100% of the power required by the load 108, and thus
the at least one power module 106 does not experience a spike in
output demand in the event of a grid 114 failure or interruption.
Accordingly, harmful spikes in output power demand from the at
least one power module 106 may be avoided.
[0090] In some embodiments, where the IOM 104 is connected to the
grid 114 (which is the "A" side feed of load 108), and the UPM 102
is connected to the "B" side feed of the load 108, the IOM output
may be greater than 50% of the output required by the load 108. For
example, if the power requirement for the load 108 is 160 kW, the
UPM 102 may provide 50% of this power (or 80 kW) to the "B"-side
feed. The IOM 104 output may be at least 80 kW, which eliminates
all utility (grid) burden from the load 108. However, the IOM 104
may be loaded to greater than 80 kW, such as 120 kW. The excess
power (40 kW in this example) may be exported to support other
needs (e.g., it may be exported into the data center or building
campus load). This type of loading arrangement allows fully
covering a critical load 108, such as an IT load, and also allows
100% asset utilization of the distributed power generation (e.g.,
fuel cell) system. In other words, the "A" side and the "B" side of
the power module 106 power output may represent greater than 100%
of the load's power requirement, such that at least a part of the
module 106 power output is provided to a facility in which the load
is located, and the module 106 output power represent approximately
100% asset utilization of the module 106.
[0091] It will be understood that the present system 700 is not
limited to data centers, and any critical power site which has a
multi corded (e.g., A, B, C, etc.) power feed architecture may
utilize the present system and method for powering a load.
[0092] In various embodiments, the IT load 108 may be an AC load
that may receive AC power at the "A" side feed from grid 114. The
power generated by the at least one power module 106 may be DC
power, and may be converted to AC power prior to being fed to the
"B" side feed of the load 108. For example, the system 700 may
include an inverter for converting DC to AC power, which may be
located in the UPM 102, or at another location between the power
module(s) 106 and the "B" side feed to the load 106. In further
embodiments, the IT load 108 may be a DC load that receives
rectified DC power from grid 114 at the "A" side feed of the load
108 (e.g., an AC/DC rectifier may be provided between the grid 114
and the "A" side feed of load 108). The "B" side feed of the load
108 may be provided with DC power from power module(s) 106 and UPM
102. Optionally, a DC/DC converter may be provided between the
power module(s) 106 and the "B" side feed, such as within UPM 102.
The DC/DC converter may condition the DC power from power module(s)
106, such as by setting the voltage to a desired point, creating
isolation and/or creating the appropriate ground reference, before
the DC power is fed to the "B" side feed of load 108. In some
embodiments, the load 108 may receive AC power at a first power
input (e.g., either the "A" side feed or the "B" side feed in a
dual-corded system), and may receive DC power at a second power
input (e.g., the other of the "A" side feed and the "B" side feed).
The load 108 may include power conditioning components (e.g.,
inverter(s), rectifier(s), converters, etc.) to condition the input
power as needed.
[0093] FIG. 7B illustrates an alternative embodiment, in which an
additional grid 714 may serve as a supplemental backup to a first
grid 114 and the at least one power module 106. As shown in FIG.
7B, a transfer switch 712 may be provided between the output of the
at least one UPM 102 and the supplemental grid (e.g., another
instance of the first grid feed, or a second grid feed) 714. The
output of the transfer switch 712 may be fed as the "B" side feed
of the data center load 108. In embodiments, in the event of a
failure of the at least one power module 106, the "B" side feed may
be provided by the supplemental grid 714.
[0094] In alternative embodiments, a power factor correction (PFC)
rectifier (e.g., insulated bipolar gate transistor [IGBT] type
rectifier) may be utilized as an alternative or in addition to a
transfer switch. The feed from the supplemental or 2.sup.nd grid
714 may be diode-OR'ed with the output from the at least one UPM
102. This may be provided as the "B" side input to the load 108,
and static switching may not be required.
[0095] FIG. 8 illustrates an embodiment system 800 for providing
power to a medical facility. High-power medical devices 808 such as
MM, X-ray, CT scan, Positron Emission Tomography (PET), and X-ray
C-Arm devices utilize power supplies which are generally medium
voltage AC (such as 480 VAC or 415 VAC) which is rectified to
approximately 600 VDC, and then fed to DC/DC converters to create
isolated, discrete DC outputs for operation of the hardware.
Significant efficiency is lost in the AC/DC conversion stage.
Furthermore, medical peaking charges are substantial because of
surge power demands.
[0096] In the embodiment system 800 shown in FIG. 8, at least one
power module 106 and associated IOM 104 may provided with at least
one Uninterruptable Power Module (UPM.sub.1) 102 paralleled into
their DC output bus 812 (e.g., +/-380 VDC bus). This configuration
is similar to that shown in FIGS. 6A-6E with respect to the ECM
described above, where the output of power modules 106 is provided
to bus 812, and the output of bus 812 is provided to IOM 104 and
UPM 102. As shown in FIG. 8, additional UPMs 102 (e.g., UPM.sub.2,
. . . UPM.sub.n) may each be similarly connected to additional
power module/IOM units (not illustrated). Each UPM 102 may include
an inverter 802 that provides an AC power output 820 (e.g., 480
VAC) and a DC/DC converter 804 that provides a DC power output 822
(e.g., 400-600 VDC). The AC output (e.g., 480 VAC) from UPM 102 may
be coupled via an AC bus 820 to the input of a medical facility
static switch 810 as a "B" side feed. The "A" side feed may be
provided from grid 114.
[0097] An IOM inverter 104A may output AC power (e.g., 480 VAC) to
the grid 114 for general export. As in the embodiment of FIG. 7,
the power output to the grid 114 from IOM 104 may be returned at
the "A" side feed of the medical facility static switch 810. Thus,
in various embodiments, during normal operation of the system 800,
no net power may be drawn from the grid 114, and all or
substantially all power required by the medical device 808 may be
provided by one or more power modules 106.
[0098] The power from static switch 810 may be provided as an input
to rectifier 818 for converting AC power (e.g., 480 VAC) to DC
power (e.g., 600 VDC), which may then be fed to the input stage of
medical device DC/DC converter 816. As discussed above, significant
efficiency may be lost in this AC/DC conversion process. As shown
in FIG. 8, the 400-600 VDC output bus 822 from UPM 102 may also be
coupled into the input stage of medical device DC/DC converter 816.
Thus, at least a portion of the DC input power to DC/DC converter
816, including all of the DC input power to DC/DC converter 816,
may be provided by PWMs 106, via the UPM, without requiring the
power to first undergo AC/DC conversion. Thus, at least a portion
of the efficiency losses associated with AC/DC conversion may be
avoided.
[0099] The medical device DC/DC converter 816 may provide a
plurality of discrete DC outputs (e.g., 700V, 100V, etc.), which
may be fed to high-fidelity amplifier 824, and then used to power
one or more medical devices 808 (MD.sub.1).
[0100] In various embodiments, more than one medical device 808 may
be coupled to the DC output of the one or more UPMs 102. As
schematically illustrated in FIG. 8, for example, medical devices
MD.sub.2 through MD.sub.n may be coupled to the 400-600 VDC output
bus 822 of UPMs 102, and may be configured similarly to MD.sub.1. A
sequencing controller 826 may be provided to control the sequence
of operation of the medical devices 108. In embodiments, the
sequencing controller 826 may be configured to provide small delays
such that the power drawn by the medical devices is balanced and
excessive peak power draws are not required. In embodiments, the
sequencing controller 826 may be configured to prioritize between
various pieces of medical equipment. For example, the sequencing
controller 826 may provide for emergency status of one or more
medical devices such that lower priority devices may be switched
off in favor of life-saving critical medical devices.
[0101] In various embodiments, the UPMs 102 may include energy
storage devices, such as the ultracapacitor 806 shown in FIG. 8. In
various embodiments, energy storage with the UPMs 102 may be
augmented with additional storage modules in order to provide
increased peak power for medical devices without creating increased
peaking charges.
[0102] In various embodiments, the UPMs 102 may be configured to
receive power from a supplemental power source 814, which may be
the grid 114, a 2.sup.nd grid or other AC generator feed to provide
backup peaking supply for the UPMs 102. In embodiments, the UPMs
102 may include a PFC corrected rectifier 805 to take in power from
supplemental power source 814 on an as-needed basis. Alternatively
or in addition, the UPM may include a static switch (not
illustrated) to take in a feed from supplemental power source 814,
such as a 2.sup.nd grid, and provide a reliable "B" side feed.
[0103] FIG. 9 illustrates a further embodiment system 900 for
providing direct DC power to a medical facility. In this system
900, the power modules 106 provide a suitable DC power output
(e.g., 600 VDC) to the input stage of the medical device DC/DC
converters 816. Multiple power module 106 unit outputs may be
paralleled for increased reliability. As shown in FIG. 9, the power
modules 106 may be configured to output +/-380 VDC (e.g., using
DC/DC converters within the power modules 106), and a second stage
of DC/DC converters 802, which may be within the UPMs 102, may
produce 600 VDC for a 600 VDC bus 822 (i.e., a "cascaded"
approach). In an alternative embodiment, two sets of DC/DC
converters may operate in parallel within the power modules 106. A
first set of DC/DC converters may produce +/-380 VDC (e.g., for
auxiliaries and/or for feed to inverter 104A in IOM 104). A second
set of DC/DC converters may produce 600 VDC for the 600 VDC bus
822. In either embodiment, the bus 822 may feed 600 VDC to the
input stage of medical device DC/DC converter 816.
[0104] As shown in FIG. 9, in embodiments the IOM 104 may include
inverter 104A, as described above. The AC power output from the
inverter 104A (e.g., 480 VAC) may be provided to the grid 114. The
power output to the grid 114 from IOM 104 may be returned to the
system 900 at UPM 102, such as via PFC corrected rectifier 805
and/or static switch as discussed above. The grid power may be
rectified and DC/DC converted to 600 VDC in UPM 102 and fed to 600
VDC bus 822. Thus, in various embodiments, during normal operation
of the system 900, no net power may be drawn from the grid 114, and
all or substantially all power required by the medical device 808
may be provided by one or more power modules 106. The power modules
106 may be operated to generate all or substantially all power
required by medical devices 108. All or a portion of the output
power from power modules 106 may be fed to grid 114 by IOM 104 and
returned at UPM 102. All or a portion of the output power from
power modules 106 may be DC power that is directly fed to the input
stage of medical device DC/DC converter 816. In the event of grid
114 failure or interruption, the system 900 may shift to 100%
direct DC power to the medical device. The power modules 106 may
not experience any significant power spikes.
[0105] Energy storage devices, such as ultracapacitor 806 shown in
FIG. 9, may be provided in the UPMs 102 (which may include
charger/discharger DC/DC converters, but may not include output
inverters in embodiments).
[0106] As shown in FIGS. 8 and 9, the UPM 102 according to various
embodiments may include an input for receiving DC power (e.g.,
+/-380 VDC) from one or more power modules 106/IOMs 104, energy
storage device(s) 806, such as ultracapacitors or batteries, for
energy storage, and may further include charging and discharging
(or bi-directional) DC/DC converters for moving energy into and out
of energy storage. As shown in FIG. 8, the UPM 102 may also include
an inverter 802, which may include inverter and transformer
circuitry to generate a suitable AC power feed (e.g., 50/60 Hz
3-wire or 4-wire 480 VAC, or other grid voltages, such as 415
VAC).
[0107] In various embodiments, a UPM 102 may also be configured to
provide a DC power output at a voltage that is different from the
input bus voltage from the one or more power modules 106. As shown
in FIGS. 8 and 9, for example, the UPM 102 includes a DC/DC
converter 804 that converts the input +/-380 VDC from bus 812 to a
different DC output voltage (e.g., 400-600 VDC, such as 600 VDC) on
bus 822. Various embodiments may include a UPM 102 that may provide
different DC output voltages, including voltages lower than the
power module input voltage, such as 12, 24, 36 and/or 48 VDC, as
well as adjustable output voltages based on a set-points, such as
0-600 VDC. In various embodiments, the output DC voltages from UPM
102 which are different from the input voltage provided by power
modules 106, may be ungrounded, may be positive with reference to
ground, and/or may be negative with reference to ground.
[0108] A typical high-power medical device 808, such as an MRI,
X-ray, CT scanner, PET scanner, C-arm device, etc., includes a
transformer and rectifier input stage in order to generate DC
voltages on the order of 600 VDC. Various embodiments may include a
medical device 808 that may utilize a direct DC feed, such as shown
in FIG. 9. By eliminating the input transformer and rectifier, the
efficiency of the device 808 may be increased while lowering the
cost of the device 808.
[0109] FIGS. 10A-10B illustrate further embodiment systems 1000,
1001 for providing a direct DC power feed to an AC load 1008. Large
AC machines are generally powered by a motor driver or load driver
or variable frequency drive system that first rectifies a grid
feed, and then from that rectified DC feed, generates AC power at
the frequency desired for AC load (e.g., motor) operation.
[0110] As shown in the system 1000 of FIG. 10A, at least one power
module 106 may generate a DC output power (e.g., +/-380 VDC). The
DC output power may be coupled to IOM 104 via bus 812. The IOM 104
may include DC/AC converter 104A for exporting output AC power to
grid 114. DC bus 812 may also be coupled to UPM 102. UPM 102 may
include DC/AC converter 802 for providing an output AC power feed
to bus 820 that may be provided as a "B" side feed at transfer
switch 1010, which may be a customer-side transfer switch. The "A"
side feed of transfer switch 1010 may be from the grid 114. The AC
power from transfer switch 1010 may be rectified at AC/DC converter
1018 to provide a DC output power (e.g., 600 VDC) which may be
connected as the middle bus of motor driver 1020. Motor driver 1020
may convert the DC power to AC power at a desired frequency for use
at AC load 1008.
[0111] UPM 102 may include DC/DC converter 804 for providing a DC
output power (e.g., 600 VDC) from input DC feed (e.g., +/-380 VDC)
from bus 812. The DC output power from UPM 102 may be provided over
DC bus 822 (e.g., 600 VDC) to the middle bus of the motor driver
1020.
[0112] FIG. 10B illustrates an alternative embodiment system 1001
in which a first DC output power from power module(s) 106 is
provided over DC bus 812 (e.g., +/-380 VDC) to IOM 104, where the
power may be converted to AC by inverter 104A and exported to grid
114, as in the system 1000 of FIG. 10A. The power module(s) 106 may
also include DC/DC converter(s) 1006 that may convert a second
portion of the DC output power to a second voltage (e.g., 600 VDC)
on bus 822 that may be directly fed to the motor driver 1020 and
converted to the desired AC frequency for AC load 1008. The
rectifier 1018 for converting AC grid power to a DC feed for motor
driver 1020 may not be required in the embodiment of FIG. 10B.
[0113] In the systems 1000, 1001 of FIGS. 10A and 10B, a DC/DC
converter 1012 (or bi-directional DC/DC converter) may be provided
such that motor 1020 braking (or device stopping) current may be
placed onto the DC (e.g., +/-380 VDC) bus 812 of the power modules
106 via DC bus 1013 and converter 1012, and thereby may be directed
to an energy storage device (such ultracapacitor 806) which may be
located in the PWM, the IOM and/or the UPM. The motor braking or
device stopping current may also be provided to the grid 114 via
the IOM inverter 104A. This is an advantage since a bi-directional
motor driver at an energy customer location may utilize braking
power, but since the motor driver inverter 1018 would typically not
have UL 1741/IEEE 1547 compliance, this power could not be exported
into the utility grid and could only be used to supply campus loads
on the energy customer side of the meter, and would otherwise have
to use resistive loads.
[0114] In further embodiments, a configuration such as shown in
FIGS. 10A and 10B may be utilized in conjunction with
electrically-powered railroad locomotives. One or more distributed
power systems, such as systems 1000, 1001 shown in FIGS. 10A and
10B, may be provided on a railway line, such as at one or more
railroad stations. Load 1008 may be a locomotive. When the
locomotive starts, DC power may be fed to the locomotive directly,
such as via DC bus 822 shown in FIGS. 10A and 10B. When the
locomotive stops, the braking power may be taken by the system
1001, 1001, such as via DC/DC converter 1012 and DC bus 1013.
[0115] The architecture such as shown in FIGS. 10A and 10B may also
be used to provide power to DC loads that use a chopper load driver
instead of a four-quadrant inverter. Loads of this nature may
include induction furnaces, for example. The configuration of FIGS.
10A and 10B may also be used to provide power to X-ray machines
used for manufacturing inspection, where the power may be fed to a
resonant converter that drives the X-ray machine.
[0116] FIG. 11 illustrates an embodiment system 1100 for powering
one or more loads 1108 using one or more power modules 106 and/or
one or more microturbine power generators 1106. As shown in FIG.
11, the power from the microturbine (M.sub.1) 1106 may be converted
to DC power by rectifier 1116, and this DC feed (e.g., 600 VDC) may
be provided to DC bus 822, which may be connected to UPM 102. The
one or more power modules 106 may be supplemented or replaced by
one or more microturbines 1106. Power from microturbine 1106 may be
provided to the UPM 102, such as via DC/DC converter 1112 and
regenerative storage device 1114 (e.g., storage battery, capacitor,
flywheel, etc.), and may be exported to the grid 114 via IOM 104.
It will be understood that one or more microturbine generators 1106
may be utilized as an alternative to or in combination with fuel
cell power modules 106 in any of the embodiments described above.
AC power may be provided to loads 1108 via the grid 114 and/or AC
bus 820 from UPM through switch 1110. Additional AC power may be
provided to loads 1108 from microturbine 1106 via DC/DC converter
1112 and inverter 1115. A direct DC feed to loads 1108 may be
provided from DC bus 822, as described above.
[0117] The various embodiments described above may include an
on-site fuel storage system. As used herein, "on site" may include
within the same building or in the vicinity (e.g., within a 0.1
mile radius) of the distributed generator (e.g., power module 106)
and/or the load. In various embodiments, the fuel may include
stored compressed natural gas (e.g., in gas storage cylinders or
vessels), stored liquid natural gas, stored liquid petroleum, such
as propane (e.g., propane tanks), ethanol, diesel, liquid hydrogen,
stored compressed hydrogen, and/or ammonia.
[0118] In various embodiments, a system for powering one or more
loads using distributed power generators, such as fuel cell power
modules, microturbines, etc., may include at least two fuel inputs
for the distributed power generator(s), where at least one of the
fuel inputs comprises fuel from an on-site fuel storage system. In
one embodiment, a first fuel input may be fuel supplied from an
off-site source (e.g., a natural gas pipeline) and a second fuel
input may be an on-site fuel storage system. The system may be
configured to shift from the first fuel input to the second fuel
input when, for example, delivery of the first fuel input has been
interrupted, the first fuel input has a cost that exceeds the
second fuel input, and/or there is a predicted interruption in the
delivery of the first fuel input (e.g., a natural disaster, such as
a tsunami or earthquake) and the second fuel input is hardened to
be more survivable in the event of such a disaster.
[0119] Various embodiments include a distributed power generation
system, comprising at least one power module comprising at least
one fuel cell segment generating an output power, a first module
comprising at least one power conditioning component electrically
coupled between the at least one power module and a grid, and a
second module comprising at least one power conditioning component
electrically coupled between the at least one power module and a
B-side power feed to a load, and wherein the A-side power feed to
the load is electrically coupled to the power module via the
grid.
[0120] In various embodiments, the second module comprises an
uninterruptible power module (UPM) that comprises an inverter for
providing an AC power output to the B-side feed of the load.
[0121] In further embodiments, the UPM comprises a DC/DC converter
for converting an input DC power feed from the power module to an
output DC power feed on a DC bus.
[0122] In further embodiments, the DC bus is electrically coupled
to the load to provide a direct DC power feed to the load.
[0123] In further embodiments, the uninterruptable power module
comprises a rectifier for taking in power from a supplemental power
source.
[0124] In further embodiments, the supplemental power source
comprises a grid.
[0125] In further embodiments, the uninterruptable power module
comprises an energy storage device.
[0126] In further embodiments, the energy storage device comprises
an ultracapacitor.
[0127] In further embodiments, at least a portion of the power to
the load may be provided by a microturbine power generator.
[0128] In further embodiments, the system comprises at least two
fuel inputs for the at least one fuel cell segment, wherein at
least one fuel input comprises a fuel that is stored on-site.
[0129] In further embodiments, in response to an expected or actual
interruption of the first fuel input or a change in relative price
between the first and second fuel inputs, the system is configured
to switch from the first fuel input to the second fuel input.
[0130] Various embodiments include a distributed power generation
system, comprising at least one power module comprising at least
one fuel cell segment generating an output power, and at least one
uninterruptible power module comprising at least one power
conditioning component electrically coupled between the at least
one power module and a direct DC power feed to a load, wherein: at
least a portion of the output power generated by the at least one
power module is provided over an input DC bus at a first voltage to
the at least one uninterruptible power module, and is provided from
the at least one uninterruptable power module over a DC output bus
at a second voltage, different than the first voltage, to the
load.
[0131] In further embodiments, the at least one power conditioning
component comprises a DC/DC converter.
[0132] In further embodiments, the second voltage is higher than
the first voltage.
[0133] In further embodiments, the second voltage is lower than the
first voltage.
[0134] In further embodiments, the at least one uninterruptable
power module is configured to provide an adjustable output voltage
over the DC output bus.
[0135] In further embodiments, the first voltage is +/-380 VDC and
the second voltage is 600 VDC.
[0136] In further embodiments, the total output power from the at
least one power module comprises at least about 100% of the total
power required to power the load.
[0137] In further embodiments, substantially no net power is drawn
from the grid to provide power to the load.
[0138] In further embodiments, at least one uninterruptable power
module comprises an inverter for converting at least a portion of
the output power generated by the at least one power module to AC
power that is provided as a B-side power feed to the load
[0139] In further embodiments, the A-side power feed to the load is
provided by a grid.
[0140] In further embodiments, the load comprises at least one of a
locomotive, an induction furnace and an x-ray machine used in
manufacturing inspection that receives DC power from the DC output
bus.
[0141] In further embodiments, the system comprises a sequencing
controller for controlling the delivery of power over DC output bus
to a plurality of loads.
[0142] In further embodiments, he sequencing controller is
configured to provide delays in the delivery of power to the loads
to minimize excessive peak power draws.
[0143] In further embodiments, the sequencing controller is
configured to control delivery of power to the loads based on a
pre-determined priority status of the loads.
[0144] Various embodiments include a method of providing power to a
load, comprising generating an output power using at least one
power module comprising at least one fuel cell segment, providing a
first portion of the output power through a grid to an A-side power
feed of the load, and providing a second portion of the output
power to a B-side power feed to the load.
[0145] In further embodiments, the method comprises providing at
least one supplemental power supply electrically coupled between
the uninterruptible power module and the B-side power feed to the
load.
[0146] In further embodiments, the supplemental power supply
comprises a second grid.
[0147] In further embodiments, the method comprises maintaining
continuous power to the load over at least one of the A-side and
the B-side feeds using a power seeking switch.
[0148] In further embodiments, the method comprises converting the
first portion of the power output from DC power to AC power using
an inverter before providing the power to the grid.
[0149] In further embodiments, the method comprises converting at
least part of the second portion of the power output from DC power
to AC power using an inverter before providing the power to the
B-side feed of the load.
[0150] In further embodiments, the method comprises converting at
least part of the second portion of the power output from DC power
at a first voltage to DC power at a second voltage, different from
the first voltage, with a DC/DC converter, and providing the DC
power at the second voltage to the load.
[0151] In further embodiments, the first voltage is +/-380 VDC and
the second voltage is 400-600 VDC.
[0152] In further embodiments, the method comprises generating
power using a microturbine, and providing power from the
microturbine to the load.
[0153] In further embodiments, the method comprises providing fuel
to the fuel cell segment using a first fuel input from a first fuel
source, and switching to a second fuel input to the fuel cell
segment from a second fuel source, wherein the second fuel source
is fuel that is stored on-site.
[0154] In further embodiments, the switching is in response to an
expected or actual interruption of the first fuel input or a change
in relative price between the first and second fuel inputs.
[0155] Various embodiments include a method of providing power to a
load, comprising generating an output power using at least one
power module comprising at least one fuel cell segment, providing a
first portion of the output power to a grid, providing a second
portion of the output power to a DC/DC converter that converts the
output power from a first voltage to a second voltage, and
providing the output power at the second voltage to the load.
[0156] In further embodiments, the second voltage is higher than
the first voltage.
[0157] In further embodiments, the second voltage is lower than the
first voltage.
[0158] In further embodiments, the second voltage is
adjustable.
[0159] In further embodiments, the first voltage is +/-380 VDC and
the second voltage is 600 VDC.
[0160] In further embodiments, providing a first portion of the
output power to a grid further comprises providing the first
portion to an inverter that converts the power from DC power to AC
power for export to the grid.
[0161] In further embodiments, the total output power from the at
least one power module comprises at least about 100% of the total
power required to power the load.
[0162] In further embodiments, substantially no net power is drawn
from the grid to provide power to the load.
[0163] In further embodiments, the method comprises providing a
third portion of the output power to an inverter that converts the
third portion to AC power, and providing the AC-converted third
portion of the output power to a B-side power feed of the load.
[0164] In further embodiments, the A-side power feed to the load is
provided by a grid.
[0165] In further embodiments, providing the output power at the
second voltage to the load comprises providing the output power at
the second voltage as an input to a medical device DC/DC converter
for providing a plurality of discrete DC outputs to power at least
one medical device.
[0166] In further embodiments, providing the output power at the
second voltage to the load comprises providing the output power at
the second voltage as an input to a motor driver for conversion to
a desired AC frequency for at least one AC load.
[0167] In further embodiments, providing the output power at the
second voltage to the load the load comprises providing the output
power at the second voltage to at least one of a locomotive, an
induction furnace and an x-ray machine used for manufacturing
inspection.
[0168] In further embodiments, the method comprises receiving
braking current from the load.
[0169] In further embodiments, the method comprises providing at
least a portion of the power from the braking current to the
grid.
[0170] In further embodiments, the method comprises storing at
least a portion of the power from the braking current in an energy
storage device.
[0171] In further embodiments, the method comprises controlling the
delivery of output power at the second voltage to a plurality of
loads.
[0172] In further embodiments, controlling the delivery comprises
providing delays in the delivery of power to the loads to minimize
excessive peak power draws.
[0173] In further embodiments, controlling the delivery comprises
delivering power to the loads based on a pre-determined priority
status of the loads.
[0174] In further embodiments, the method comprises generating at
least a portion of the power for the load using at least one
microturbine power generator.
[0175] The foregoing method descriptions are provided merely as
illustrative examples and are not intended to require or imply that
the steps of the various embodiments must be performed in the order
presented. As will be appreciated by one of skill in the art the
order of steps in the foregoing embodiments may be performed in any
order. Further, words such as "thereafter," "then," "next," etc.
are not intended to limit the order of the steps; these words are
simply used to guide the reader through the description of the
methods.
[0176] One or more block/flow diagrams have been used to describe
exemplary embodiments. The use of block/flow diagrams is not meant
to be limiting with respect to the order of operations performed.
The foregoing description of exemplary embodiments has been
presented for purposes of illustration and of description. It is
not intended to be exhaustive or limiting with respect to the
precise form disclosed, and modifications and variations are
possible in light of the above teachings or may be acquired from
practice of the disclosed embodiments. It is intended that the
scope of the invention be defined by the claims appended hereto and
their equivalents.
[0177] Control elements (e.g., controller 826) may be implemented
using computing devices (such as computer) comprising processors,
memory and other components that have been programmed with
instructions to perform specific functions or may be implemented in
processors designed to perform the specified functions. A processor
may be any programmable microprocessor, microcomputer or multiple
processor chip or chips that can be configured by software
instructions (applications) to perform a variety of functions,
including the functions of the various embodiments described
herein. In some computing devices, multiple processors may be
provided. Typically, software applications may be stored in the
internal memory before they are accessed and loaded into the
processor. In some computing devices, the processor may include
internal memory sufficient to store the application software
instructions.
[0178] The various illustrative logical blocks, modules, circuits,
and algorithm steps described in connection with the embodiments
disclosed herein may be implemented as electronic hardware,
computer software, or combinations of both. To clearly illustrate
this interchangeability of hardware and software, various
illustrative components, blocks, modules, circuits, and steps have
been described above generally in terms of their functionality.
Whether such functionality is implemented as hardware or software
depends upon the particular application and design constraints
imposed on the overall system. Skilled artisans may implement the
described functionality in varying ways for each particular
application, but such implementation decisions should not be
interpreted as causing a departure from the scope of the present
invention.
[0179] The hardware used to implement the various illustrative
logics, logical blocks, modules, and circuits described in
connection with the aspects disclosed herein may be implemented or
performed with a general purpose processor, a digital signal
processor (DSP), an application specific integrated circuit (ASIC),
a field programmable gate array (FPGA) or other programmable logic
device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the
functions described herein. A general-purpose processor may be a
microprocessor, but, in the alternative, the processor may be any
conventional processor, controller, microcontroller, or state
machine. A processor may also be implemented as a combination of
computing devices, e.g., a combination of a DSP and a
microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration. Alternatively, some blocks or methods may be
performed by circuitry that is specific to a given function.
[0180] The preceding description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
described embodiment. Various modifications to these embodiments
will be readily apparent to those skilled in the art, and the
generic principles defined herein may be applied to other
embodiments without departing from the scope of the disclosure.
Thus, the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope
consistent with the following claims and the principles and novel
features disclosed herein.
* * * * *