U.S. patent application number 15/898114 was filed with the patent office on 2018-07-05 for smart renewable energy system with grid and dc source flexibility.
The applicant listed for this patent is CyboEnergy, Inc.. Invention is credited to George Shu-Xing CHENG, Steven L. MULKEY.
Application Number | 20180191167 15/898114 |
Document ID | / |
Family ID | 56554807 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180191167 |
Kind Code |
A1 |
CHENG; George Shu-Xing ; et
al. |
July 5, 2018 |
SMART RENEWABLE ENERGY SYSTEM WITH GRID AND DC SOURCE
FLEXIBILITY
Abstract
A method and apparatus is disclosed relating to smart renewable
power generation systems with grid and DC source flexibility that
can (1) intelligently and selectively pull power from one or
multiple DC sources including solar panels, wind generators, and
batteries based on certain criteria; (2) invert DC power to AC
power; (3) supply the AC power to the electric grid or to an
off-grid electric circuit to power AC loads; (4) supply DC power
through one or multiple DC output ports to power DC loads; and (5)
charge batteries. Various types of on-grid, off-grid, and
on/off-grid DC flexible power inverters are described to
demonstrate the innovation for delivering flexible, cost-effective,
and user-friendly power generation systems to harvest any form of
renewable energy available and convert it to usable
electricity.
Inventors: |
CHENG; George Shu-Xing;
(Folsom, CA) ; MULKEY; Steven L.; (Cameron Park,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CyboEnergy, Inc. |
Rancho Cordova |
CA |
US |
|
|
Family ID: |
56554807 |
Appl. No.: |
15/898114 |
Filed: |
February 15, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15009658 |
Jan 28, 2016 |
9906038 |
|
|
15898114 |
|
|
|
|
62109427 |
Jan 29, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02B 10/10 20130101;
H02J 3/383 20130101; Y02E 10/56 20130101; Y02B 10/14 20130101; H02J
7/35 20130101; H02J 2300/24 20200101; H02J 1/10 20130101; Y02B
10/30 20130101; Y02E 10/566 20130101; H02J 3/381 20130101; H02J
3/382 20130101; H02J 2300/20 20200101; Y02E 10/563 20130101 |
International
Class: |
H02J 3/38 20060101
H02J003/38; H02J 1/10 20060101 H02J001/10; H02J 7/35 20060101
H02J007/35 |
Claims
1. A scalable DC to AC power inversion system for providing AC
power to an electric grid from a plurality of individual DC power
sources each having a DC output port, comprising: a) at lease one
on-grid power inverter, each having an on-grid AC output port and
multiple DC input ports constructed and arranged to be connected to
multiple DC power sources including at least one photovoltaic solar
panel, at least one wind generator, or at least one battery, or any
combination thereof; b) each power inverter being constructed and
arranged to pull DC power from one or multiple DC input ports based
on pre-defined DC source selection criteria; c) the on-grid AC
output port of each inverter being combined in parallel to supply
AC power to the grid; and d) whereby said system is incrementally
scalable by adding or subtracting DC power sources and
inverters.
2. The scalable DC to AC power inversion system of claim 1, in
which the DC source selection criteria of each on-grid power
inverter comprises: (a) maximizing the harvest of solar and wind
energy and supplying generated AC power to the electric grid; (b)
pulling power or stop pulling power from the battery based on power
dispatch commands from an independent grid system operator (ISO)
that manages the electric grid so the generated AC power is ramped
up and down for grid stabilization; and (c) charging battery when
there is excess DC power from solar or wind.
3. The scalable DC to AC power inversion system of claim 1, in
which the output of each said power inverter is single-phase AC or
three-phase AC.
4. A method of making an on/off-grid DC source flexible power
generation system incrementally scalable, comprising: a) providing
a plurality of DC power sources and a plurality of on/off-grid
power inverters, each having an on-grid AC output port, an off-grid
AC output port, and at least one DC input port; b) connecting DC
input ports to multiple DC sources including at least one
photovoltaic solar panel, at least one wind generator, or at least
one battery, or any combination thereof; c) pulling power from the
connected DC sources based on pre-defined DC source selection
criteria; and d) providing AC power to an electric grid through
said on-grid AC output ports when the grid is on or providing AC
power to one or multiple AC loads, individually, through said
off-grid AC output port of each inverter when the grid is down.
5. The method of claim 4, further comprising: a) each of said
inverters having an on-grid AC input port; b) combining said
on-grid AC output port of all inverters together by daisy-chaining
the inverters, said on-grid AC output port of each inverter being
connected in a daisy chain to the on-grid AC input port of the next
inverter, except for the on-grid AC output port of the first
inverter being connected to the electric grid, and the on-grid AC
input port of the last inverter being left open; and c) providing
AC power to the electric grid through the on-grid AC output port of
the first inverter when the grid is on.
6. The method of claim 4, further comprising: a) combining said
off-grid AC output port of all inverters together so the total
produced AC power is the summation of the AC power supplied by each
inverter; and b) providing AC power to one or multiple AC loads
through the combined off-grid AC output ports when the grid is
down.
7. The method of claim 4, in which the DC source selection criteria
comprises: (a) maximizing the harvest of solar and wind energy and
supplying generated AC power to an electric grid when the grid is
on; (b) providing sufficient AC power to run the connected AC loads
without using battery power when the grid is down; (c) pulling
power from battery to meet the power demand when solar and wind
cannot produce sufficient DC power for the system to run the
connected AC loads; and (d) charging battery when there is excess
DC power from solar or wind.
8. The method of claim 4, in which the DC source selection criteria
further comprises pulling power or stop pulling power from the
battery based on power dispatch commands from an independent grid
system operator (ISO) that manages the electric grid so the
generated AC power is ramped up and down for grid stabilization
when grid is on.
9. The method of claim 4, in which the output of each said power
inverter is single-phase AC or three-phase AC.
10. The method of claim 4, further comprising: a) connecting a
first DC power source to one of said DC power input ports of one of
said power inverters; and b) connecting a second DC power source,
different in kind from said first DC power source, to another of
said DC power input ports of said one power inverter.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/009,658 filed on Jan. 28, 2016, which
claims priority to its filing date, which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The subject of this patent relates to renewable electric
power generation and DC (direct current) to AC (alternating
current) power inverters that invert DC power from single or
multiple DC sources to single-phase or three-phase AC power, where
the DC sources include but are not limited to photovoltaic (PV)
solar modules or panels, PV cells, PV materials, PV thin films,
fuel cells, batteries, wind generators, bio-fuel generators, and
other DC power generators. More particularly, this patent relates
to smart renewable power generation systems with grid and DC source
flexibility that can (1) intelligently and selectively pull power
from one or multiple DC sources based on certain criteria; (2)
invert DC power to AC power; (3) supply the AC power to the
electric grid or to an off-grid electric circuit to power AC loads;
(4) supply DC power through one or multiple DC output ports to
power DC loads; and (5) charge batteries. The DC source selection
criteria are implemented in computer software, which is
configurable to achieve desirable functions for a specific
application.
[0003] In the U.S. Pat. No. 8,786,133, the entirety of which is
hereby incorporated by reference, we described the novel Smart and
Scalable Power Inverters and the unique scalable design so that the
DC to AC power inversion system can include as few as one inverter
and one DC source, up to a selected number of inverters and
multiple DC sources. A number of smart single-input, dual-input,
triple-input, quad-input, and multiple-input power inverters in a
mixed variety can easily connect to single, dual, triple, quad, and
multiple DC power sources, invert the DC power to AC power, and
daisy chain together to generate a total power, which is equal to
the summation of the AC power supplied by each smart and scalable
power inverter.
[0004] In the U.S. patent application Ser. No. 13/493,622, the
entirety of which is hereby incorporated by reference, we described
the Smart and Scalable Off-Grid Mini-Inverters having one or
multiple DC input channels that can invert DC power to AC power,
and supply AC power to power electrical devices including motors,
pumps, fans, lights, appliances, and homes.
[0005] In the U.S. patent application Ser. No. 13/537,206, the
entirety of which is hereby incorporated by reference, we described
an enclosure design to accommodate and support the unique features
and capabilities of the Smart and Scalable Power Mini-Inverters
that have multiple input channels, and a messaging system using
LEDs mounted on the enclosure to indicate the system status of the
Smart and Scalable Mini-Inverters.
[0006] In the U.S. patent application Ser. No. 13/789,637, the
entirety of which is hereby incorporated by reference, we described
a method and apparatus for maximizing power production for solar
power systems when there is low sunlight during sunrise, sunset,
clouding, partial shading, and other low irradiance conditions. A
multiple-channel solar power Mini-Inverter can work in the low
power mode when there is low sunlight, take power from one solar
module to supply DC power to its internal electronic circuits, and
also invert the DC power from the remaining connected solar modules
to AC power feeding to the electric grid or powering AC loads.
[0007] In the U.S. patent application Ser. No. 13,844/484, the
entirety of which is hereby incorporated by reference, we described
a method and apparatus that can monitor the solar power inverters
in real-time both day and night, and generate surveillance alarms
and actions when a solar power inverter is removed or disconnected
from the AC powerline for no good reason. It offers a low cost and
reliable surveillance means to help guard a residential,
commercial, or utility-scale solar power system in real-time.
[0008] In the U.S. patent application Ser. No. 13/846,708, the
entirety of which is hereby incorporated by reference, we described
a method and apparatus for solar power generation when irradiance
changes quickly or is very low due to sunrise, sunset, clouding,
partial shading, warped PV surfaces, moving solar modules, and
other low or varying irradiance conditions. A multi-channel solar
power inverter connected to multiple solar modules can work in a
"Lunar Power Mode", inverting DC power induced from the sky, street
lights, or surrounding environment to AC power.
[0009] In the U.S. patent application No. 62/087,644, the entirety
of which is hereby incorporated by reference, we described a method
and apparatus that can intelligently invert DC power from single or
multiple DC sources to single-phase or three-phase AC power, supply
the AC power to the electric power grid when the grid is on, or
supply AC power to electric devices or loads when the grid is down.
A Smart and Grid flexible Power Inverter, or On/Off-Grid Power
Inverter, is disclosed that can work in either the on-grid or
off-grid mode, and switch back and forth between the two modes
manually or automatically depending on the power grid
conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] In this patent, we disclose renewable power generation
systems with grid and DC source flexibility. In the accompanying
drawing:
[0011] FIG. 1 is a block diagram illustrating a traditional
off-grid solar power system as prior art, where the battery is a
necessary component of the system.
[0012] FIG. 2 is a block diagram illustrating a grid flexible and
DC source flexible power generation system where one m+2 channel
on/off-grid DC source flexible power inverter is connected to m
solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0013] FIG. 3 is a block diagram illustrating an on-grid DC source
flexible power generation system where one m+2 channel on-grid DC
source flexible power inverter is connected to m solar panels, a
battery set, and a wind generator through corresponding DC input
channels, according to an embodiment of this invention.
[0014] FIG. 4 is a block diagram illustrating an off-grid DC source
flexible power generation system where one m+2 channel standalone
off-grid DC source flexible power inverter is connected to m solar
panels, a battery set, and a wind generator through corresponding
DC input channels, according to an embodiment of this
invention.
[0015] FIG. 5 is a block diagram illustrating an off-grid DC source
flexible power generation system where one m+2 channel off-grid DC
flexible power inverter is connected to m solar panels, a battery
set, and a wind generator through corresponding DC input channels,
according to an embodiment of this invention.
[0016] FIG. 6 is a block diagram illustrating a combined on-grid
and on/off-grid, DC source flexible power generation system where
one m+2 channel on-grid DC flexible power inverter and one m+2
channel on/off-grid DC flexible power inverter daisy-chain to form
a group, each inverter is connected to m solar panels, a battery
set, and a wind generator through corresponding DC input channels,
according to an embodiment of this invention.
[0017] FIG. 7 is a block diagram illustrating a grid flexible and
DC source flexible power generation system where one m+2 channel
and one m+1 on/off-grid DC flexible power inverters daisy-chain to
form a group, each inverter is connected to m solar panels and a
battery set, and the m+2 inverter also connects to a wind
generator, according to an embodiment of this invention.
[0018] FIG. 8 is a block diagram illustrating a m+2 channel
on/off-grid DC source flexible power inverter that is connected to
m solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0019] FIG. 9 is a block diagram illustrating a m+1 channel
on/off-grid DC source flexible power inverter that is connected to
m solar panels and a battery set through corresponding DC input
channels, according to an embodiment of this invention.
[0020] FIG. 10 is a block diagram illustrating a m+2 channel DC
source flexible on-grid power inverter that is connected to m solar
panels, a battery set, and a wind generator through corresponding
DC input channels, according to an embodiment of this
invention.
[0021] FIG. 11 is a block diagram illustrating a m+2 channel DC
source flexible off-grid power inverter that is connected to m
solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0022] FIG. 12 is a block diagram illustrating a m+1 channel
off-grid DC source flexible power inverter that is connected to m
solar panels and a battery set through corresponding DC input
channels, according to an embodiment of this invention.
[0023] FIG. 13 is a block diagram illustrating a m+1 channel DC
source flexible on-grid power inverter that is connected to m solar
panels and a battery set through corresponding DC input channels,
according to an embodiment of this invention.
[0024] FIG. 14 is a block diagram illustrating a m+1 channel DC
source flexible on-grid power inverter that is connected to m solar
panels and a wind generator through corresponding DC input
channels, according to an embodiment of this invention.
[0025] FIG. 15 is a block diagram illustrating a DC selector and
converter mechanism, according to an embodiment of this
invention.
[0026] FIG. 16 is a block diagram illustrating a DC power combiner
and splitter mechanism, according to an embodiment of this
invention.
[0027] FIG. 17 is a block diagram illustrating a battery charge
controller with one or multiple DC inputs, according to an
embodiment of this invention.
[0028] The term "mechanism" is used herein to represent hardware,
software, or any combination thereof. The term "solar panel" or
"solar module" refers to photovoltaic (PV) solar modules. The term
"AC load" is used herein to represent one or more single-phase or
three-phase electrical devices including but not limited to motors,
pumps, fans, lights, appliances, and homes.
[0029] Throughout this document, m=1, 2, 3, . . . , as an integer,
which is used to indicate the number of the DC input ports of an
inverter. The term "input channel" refers to the DC input port of
the inverter. Then, a m-channel inverter means that the inverter
has m input channels or m DC input ports. The term "m-channel
inverter" refers to an inverter that has m input channels, where
m=1, 2, 3, . . . , as an integer.
[0030] Throughout this document, a DC source can be in any one of
the following forms including a solar panel or a set of solar
panels combined in series and/or parallel, a battery or a set of
batteries combined in series and/or parallel, a fuel cell or a set
of fuel cells combined in series and/or parallel, a wind generator,
and other types of DC power generators. If a power inverter is used
to generate single-phase AC, it can also be applied to three-phase
AC without departing from the spirit or scope of our invention. If
a solar inverter is used to generate three-phase AC, it can also be
applied to single-phase AC without departing from the spirit or
scope of our invention. The AC power and related electric grid and
AC load can be either single-phase, split-phase, or
three-phase.
[0031] Without losing generality, all numerical values given in
this patent are examples. Other values can be used without
departing from the spirit or scope of our invention. The
description of specific embodiments herein is for demonstration
purposes and in no way limits the scope of this disclosure to
exclude other not specially described embodiments of this
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] In 2014, the most widespread epidemic of Ebola virus disease
in history has been ongoing in several West African countries. It
has caused significant mortality with a reported 71% case fatality
rate. Most of the seriously affected areas have limited access to
running water and soap needed to help control the spread of
disease. While this patent is being written, an associate is
traveling in West Africa, trying to install solar power systems to
help meet the urgent demand. He witnessed the devastation and lack
of infrastructure including electricity and running water.
Basically, people need electricity and water in any form that they
can get. So the demand is high and the motivation is clear. The
question is how can we build and supply simple and flexible power
generation systems to keep the lights on and vaccines refrigerated
in clinics that have no electricity.
[0033] In this patent, we disclose smart renewable power generation
systems with grid and DC source flexibility to harvest any form of
renewable energy available and convert it to usable
electricity.
[0034] FIG. 1 is a block diagram illustrating a traditional
off-grid solar power system, as prior art, where the battery is a
necessary component of the system. The system comprises multiple
solar panels 10, a solar charge controller 12, a single battery or
a battery set 14, a DC-AC power inverter 16, and AC loads 18.
[0035] A battery set is a set of batteries that are connected in
parallel and/or in series to provide higher DC voltage and current.
For instance, three 12V batteries can be connected in series to
become a 36V battery. The solar panels are combined in series
and/or parallel to supply DC power to the solar charge controller
which connects to the battery set for charging. The solar charge
controller takes DC power from the solar panels and charges the
batteries. The DC-AC power inverter takes DC power from the battery
set, inverts the DC to AC power, and outputs AC to power the AC
loads.
[0036] FIG. 2 is a block diagram illustrating a grid flexible and
DC source flexible power generation system where one m+2 channel
on/off-grid DC source flexible power inverter is connected to m
solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0037] The system comprises a m+2 channel on/off-grid DC flexible
power inverter 20, an inverter's on-grid AC power output port 22,
an inverter's off-grid AC power output port 24, inverter's multiple
DC input channels 26 that connect to m solar panels 28,
respectively, an inverter's battery input channel 30 that connects
to a battery set 32, and an inverter's wind power input channel 34
that connects to a wind generator 36. In addition, the system
comprises an on-grid AC powerline 38, an electric service panel 40,
a power grid 42, an off-grid AC powerline 44, and AC loads 46.
[0038] In this grid and DC source flexible power generation system,
the on/off-grid DC flexible power inverter can (1) intelligently
and selectively pull power from the solar panels, wind generator,
and battery based on certain criteria; (2) invert DC power from one
or multiple DC sources to AC power; (3) supply the AC power to the
electric grid or to an off-grid electric circuit to power electric
devices; and (4) charge the battery. As an on/off-grid power
inverter, it can output the AC power to the electric grid 42 via
the AC powerline 38 and the electric service panel 40 while the
grid is on, or output AC power to the AC loads 46 via the AC
powerline 44 while the grid is down.
[0039] In the embodiments herein, the battery charging operation
has to meet certain conditions including: (1) the power provided by
the solar panels and wind generator is sufficient, and (2) the
battery is below a pre-determined level.
[0040] In the embodiments herein, the solar panel can be a silicon
or thin film type photovoltaic (PV) solar panel or a set of solar
panels combined in series and/or parallel; the battery can be a
lead-acid, Lithium-Ion, fuel-cell, or other type of battery or a
set of batteries combined in series and/or parallel; the wind
generator can be any type of wind generators that produce DC power
or an AC wind generator whose AC output can be converted to DC
using a rectifier device. The wind generator should have over-speed
protection mechanism and produce DC power with appropriate voltage,
current, and wattage. The AC power and related electric grid as
well as AC loads can be single-phase, split-phase, or three-phase.
The 2 AC wires 38 and 44 in FIG. 2 and in the other embodiments to
be described in this patent are used to show the concept and
method.
[0041] A smart renewable power generation system with DC source
flexibility should include the following functions: (1) pull all
available DC power from all solar panels at its maximum power point
(MPP); (2) charge the battery if there is excess DC power from the
solar panels and/or wind generator; (3) be able to select and pull
power from available DC sources based on certain criteria; (4) be
able to combine all available DC power from solar, wind, and
battery to meet the production demand on the AC side for both
on-grid and off-grid applications; and (5) implement the DC source
selection criteria in computer software, which is configurable to
achieve desirable functions for a specific application.
[0042] As an example, in the on-grid mode, the DC source selection
criteria can be designed with the following options: (1) maximize
the harvest of solar and wind energy and supply the generated AC
power to the grid; and (2) charge battery if there is excess wind
power which enters the charge controller directly. In the off-grid
mode, the DC source selection criteria can be designed with the
following options: (3) provide sufficient AC and DC output power to
run the connected AC and DC loads without using the battery power;
(4) if solar and wind cannot produce sufficient DC power for the
system to run the connected loads, pull power from the battery to
meet the DC power demand; (5) charge battery if there is sufficient
wind power which enters the charge controller directly; and (6)
charge battery if there is excess DC power from the solar panels in
order to run the connected AC and DC loads.
[0043] The essence of the DC source selection criteria is about
balancing the input and output power, while achieving the defined
objectives. The criteria is implemented in the software running in
a digital microcontroller in the power inverter to be described in
FIGS. 8 to 14. To determine the DC input power and AC output power,
voltage and current sensors for both DC inputs and AC output are
installed in the inverter. Power is calculated by multiplying
voltage and current. The digital microcontroller uses the DC input
and AC output power information to balance the input and output
power.
[0044] FIG. 3 is a block diagram illustrating an on-grid DC source
flexible power generation system where one m+2 channel on-grid DC
source flexible power inverter is connected to m solar panels, a
battery set, and a wind generator through corresponding DC input
channels, according to an embodiment of this invention.
[0045] The system comprises a m+2 channel on-grid DC source
flexible power inverter 50, an inverter's AC power output port 52,
an inverter's AC power input port 54, inverter's multiple DC input
channels 56 that connect to m solar panels 58, respectively, an
inverter's battery input channel 60 that connects to a battery set
62, and an inverter's wind power input channel 64 that connects to
a wind generator 66. In addition, the system comprises an on-grid
AC powerline 68, an electric service panel 70, a power grid 72, an
on-grid AC powerline 74 that connects AC power input port 54 to the
AC outputs from other on-grid or on/off-grid power inverters.
[0046] In this on-grid and DC source flexible power generation
system, the on-grid DC flexible power inverter can (1)
intelligently and selectively pull power from the solar panels,
wind generator, and/or battery based on certain criteria; (2)
invert DC power from one or multiple DC sources to AC power; (3)
supply the AC power to the electric grid 72 via the AC powerline 68
and the electric service panel 70; and (4) charge the battery.
[0047] FIG. 4 is a block diagram illustrating an off-grid DC source
flexible power generation system where one m+2 channel standalone
off-grid DC source flexible power inverter is connected to m solar
panels, a battery set, and a wind generator through corresponding
DC input channels, according to an embodiment of this
invention.
[0048] The system comprises a m+2 channel standalone off-grid DC
source flexible power inverter 80, two inverter's DC power output
ports 82, an inverter's AC power output port 84, inverter's
multiple DC input channels 86 that connect to m solar panels 88,
respectively, an inverter's battery input channel 90 that connects
to a battery set 92, and an inverter's wind power input channel 94
that connects to a wind generator 96. In addition, the system
comprises two DC loads 99 that are connected to inverter's DC
output ports 82, respectively, and an off-grid AC powerline 97 that
connects to inverter's AC output port 84 to supply AC power to AC
loads 98.
[0049] In this off-grid DC source flexible power generation system,
the off-grid DC source flexible power inverter can (1)
intelligently and selectively pull power from the solar panels,
wind generator, and/or battery based on certain criteria; (2)
supply DC power through DC output ports to power one or multiple DC
loads; (3) invert DC power from one or multiple DC sources to AC
power; (4) supply the AC power to the AC loads; and (5) charge the
battery.
[0050] This is a simple yet useful off-grid solar power system.
Compared with the off-grid solar power system in FIG. 1, it has
many features and benefits including: (1) the battery is not a
necessary component for the system to be operational so that
battery-less off-grid power generation systems can be implemented;
(2) when there is sufficient sunlight or wind, the inverter will
pull power from the solar panels and/or wind generator to run the
AC and DC loads, while leaving the battery idle to extend its life;
(3) it can charge the battery if there is sufficient DC power from
the solar panels or wind generator; and (4) it can pull power from
the battery when more DC power is needed in order to run the
connected loads. To conclude, this is a much more powerful and
flexible off-grid power generation system that can power AC loads
including lights, fans, TVs, computers, battery chargers,
refrigerators, motors, pumps, and home appliances as well as DC
loads including battery chargers, lights, tools, instruments, DC
pumps, DC motors, and other devices requiring DC to run.
[0051] FIG. 5 is a block diagram illustrating an off-grid DC source
flexible power generation system where one m+2 channel off-grid DC
flexible power inverter is connected to m solar panels, a battery
set, and a wind generator through corresponding DC input channels,
according to an embodiment of this invention.
[0052] The system comprises a m+2 channel off-grid DC source
flexible power inverter 100, an inverter's AC power output port
102, an inverter's AC power input port 104, inverter's multiple DC
input channels 106 that connect to m solar panels 108,
respectively, an inverter's battery input channel 110 that connects
to a battery set 112, and an inverter's wind power input channel
114 that connects to a wind generator 116. In addition, the system
comprises an off-grid AC powerline 117 that connects to the
inverter's AC output port 102 to supply AC power to AC loads 118.
The system also comprises an off-grid AC powerline 119 that
connects other inverter's off-grid AC outputs to the AC input port
104. The off-grid AC input port allows the inverter to daisy-chain
with other off-grid or on/off-grid power inverters to form a larger
off-grid AC circuit to power AC loads that require more power.
[0053] The smart and scalable off-grid power inverters have been
described in the U.S. patent application Ser. No. 13/493,622, where
multiple off-grid inverters can work together as a group, in which
an AC master inverter is the "leading inverter" to generate AC
power to the off-grid AC powerline to allow the other off-grid
inverters connected to the same AC powerline to synchronize with
the AC power being produced by the AC master inverter.
[0054] In physical design of a m+2 channel off-grid DC flexible
power inverter, the AC input port and AC output port can be
constructed by using appropriate AC wires and connectors to make
the installation more user-friendly. For instance, the AC output
port can use a male-type AC connector and the AC input port can use
a female-type AC connector, which make a matching pair. This way,
the user can easily make the AC connections and avoid potential
errors.
[0055] FIG. 6 is a block diagram illustrating a combined on-grid
and on/off-grid, DC source flexible power generation system where
one or multiple m+2 channel on-grid DC flexible power inverters and
one m+2 channel on/off-grid DC flexible power inverter daisy-chain
to form a group, each inverter is connected to m solar panels, a
battery set, and a wind generator through corresponding DC input
channels, according to an embodiment of this invention.
[0056] Without losing generality, the system comprises one or more
m+2 channel on-grid DC source flexible power inverters 120, each of
which has (1) m DC input channels 126 that are connected to m solar
panels 128, respectively, (2) a battery channel 130 that is
connected to a battery set 132, and (3) a wind channel 134 that is
connected to a wind generator 136. The system also comprises a m+2
channel on/off-grid DC source flexible power inverter 140, which
has (4) m DC input channels 146 that are connected to m solar
panels 148, respectively, (5) a battery channel 150 that is
connected to a battery set 152, and (6) a wind channel 154 that is
connected to a wind generator 156.
[0057] The m-channel on-grid power inverters are disclosed in U.S.
Pat. No. 8,786,133 and subsequent patent applications. A m+2
channel on-grid DC source flexible power inverter is similar. It
has m input channels that can connect to m DC source such as solar
panels. It also has an additional battery channel to connect a
battery set and a wind channel to connect to a wind generator. So,
it has m+2 input channels.
[0058] Each m+2 channel on-grid power inverter 120 comprises an AC
output port 122 and an AC input port 124. The on-grid inverters can
daisy chain, where the AC output port of an inverter connects to
the AC input port of the next inverter, and so on. The first
inverter's AC input port is left open, and the last inverter's AC
output port is connected to an AC electric service panel so that
the generated AC power can be sent to the grid. This method greatly
simplifies the wiring job when installing a solar power system.
[0059] Although we say the inverters daisy chain, where the AC
output port of each inverter is connected to the AC input port of
the next inverter, the actual connection of the inverters is
pass-through. That means, the generated AC power from each inverter
is added in parallel onto the AC powerline.
[0060] In FIG. 6, the m+2 channel on/off-grid power inverter 140
comprises an on-grid AC output port 142 and an off-grid AC output
port 144. Its on-grid AC output port 142 can daisy-chain with the
AC input port 124 of the first on-grid inverter 120. This way, all
the inverters are daisy-chained through the on-grid AC powerline
158. The off-grid AC output port 144 of the on/off-grid inverter
140 is connected to an off-grid AC powerline 164 to form an
off-grid AC circuit.
[0061] In this combined on-grid and on/off-grid DC source flexible
power generation system, each inverter takes power from its
corresponding DC sources and inverts the DC power to AC power. When
the grid is on, the combined AC power from all inverters 120 and
140 is sent to the power grid 162. When the grid is down, the AC
power from the off-grid AC output port of the on/off-grid inverter
140 powers the AC loads 166.
[0062] Since these DC source flexible power inverters get DC power
from solar, battery, and wind, they can be designed to include the
following functions: (1) pull all available DC power from all solar
panels at its maximum power point (MPP); (2) charge the battery if
there is excess DC power from the solar panels and/or wind
generator; (3) be able to select and pull power from available DC
sources based on certain criteria; (4) be able to combine all
available DC power from solar, wind, and battery to meet the
production demand on the AC side for both on-grid and off-grid
applications; and (5) implement the DC source selection criteria in
computer software, which is configurable to achieve desirable
functions for a specific application.
[0063] FIG. 7 is a block diagram illustrating a grid flexible and
DC source flexible power generation system where one m+2 channel
and one m+1 on/off-grid DC flexible power inverters daisy-chain to
form a group, each inverter is connected to m solar panels and a
battery set, and the m+2 inverter also connects to a wind
generator, according to an embodiment of this invention.
[0064] Without losing generality, the system comprises one m+2
channel on/off-grid DC source flexible power inverter 170, which
has (1) m DC input channels 176 that are connected to m solar
panels 178, respectively, (2) a battery channel 180 that is
connected to a battery set 182, and (3) a wind channel 184 that is
connected to a wind generator 186. The system also comprises a m+1
channel on/off-grid DC source flexible power inverter 190, which
has (4) m DC input channels 196 that are connected to m solar
panels 198, respectively, and (5) a battery channel 200 that is
connected to a battery set 202. Notice that the m+1 channel power
inverter does not include a wind channel in this case. There can be
numerous combination possibilities where different inverters in the
same family can be combined to form a group.
[0065] In this system, the on/off-grid power inverter 170 comprises
an on-grid AC output port 172, and on-grid AC input port 173, and
an off-grid AC output port 174. The on/off-grid power inverter 190
comprises an on-grid AC output port 192, and on-grid AC input port
193, and an off-grid AC output port 194. The two inverters can
daisy-chain by connecting the AC output port 192 of inverter 190 to
the AC input port 173 of inverter 170. Each on/off-grid inverter
takes power from its corresponding DC sources, inverts the DC power
to AC power, and outputs the AC power through either the on-grid AC
output or off-grid AC output port depending on the grid condition.
When the grid is on, the combined AC power from all inverters 170
and 190 is sent to the power grid 206 via the AC powerline 204.
When the grid is down, the AC power from the off-grid AC output
port 174 and 194 of the inverter 170 and 190 powers their
corresponding AC loads 208 via the AC powerline 207, respectively.
To simplify the drawing, FIG. 7 shows only one inverter for both
170 and 190, although there can be multiple inverters in the system
that are connected in similar ways.
[0066] FIG. 8 is a block diagram illustrating a m+2 channel
on/off-grid DC source flexible power inverter that is connected to
m solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0067] The inverter comprises m DC selector and converter circuits
301, 302, . . . , 304, a DC power combiner and splitter 306, a
DC-AC inverter 308, a load interface circuit 310, an internal
on-grid AC powerline 312, an on-grid electric relay 314, a digital
microcontroller 316, a line sensing circuit 318, an interface
circuit for powerline communications 320, a powerline
communications Modem 322, a load detector 324, an internal off-grid
AC powerline 326, an off-grid electric relay 328, an external
on-grid AC powerline 330, an external off-grid AC powerline 332, an
internal DC power supply 334, a battery charge controller 336, an
external DC power supply 338, and DC output circuits 339. The
external on-grid AC powerline 330 is connected to an electric grid,
and the external off-grid AC powerline 332 is connected to an
off-grid AC circuit.
[0068] A smart on/off-grid power inverter is disclosed in the U.S.
patent application No. 62/087,644 that can work in either the
on-grid or off-grid mode, and switch back and forth between the two
modes manually or automatically depending on the power grid
conditions. The m+2 channel on/off-grid DC source flexible power
inverter works similarly but includes additional features and
capabilities.
[0069] During normal operating conditions, the power from solar
panels 291, 292, . . . , 294 is delivered to the corresponding DC
selector and converter 301, 302, . . . , 304 respectively. The
power from wind generator 298 can enter the DC selector and
converter 301, 302, . . . , 304 simultaneously as the wind
generator's DC output is connected to each of the converters in
parallel. The power from battery 296 can also enter the DC selector
and converter 301, 302, . . . , 304 simultaneously as its DC output
is connected to each of the converters in parallel. The drawings in
FIGS. 2 to 7 show that there are only one battery channel and one
wind channel, which reflect this design.
[0070] Each DC selector and converter 301, 302, . . . , 304 is
controlled by the microcontroller 316 and can select one or more DC
sources from solar, wind, and battery depending on the DC selection
criteria, which is implemented in the software in microcontroller
316. Each DC selector and converter can pull power from the
selected DC sources and combine the power. It then splits the DC
power into a high-voltage (HV) and a low-voltage (LV) output. These
2 outputs are connected to the DC power combiner and splitter 306
as illustrated by the 2 lines in FIG. 8. The detailed design for
the DC selector and converter 301, 302, . . . , 304, and those to
be described in the embodiments herein will be disclosed in FIG.
15.
[0071] The DC power combiner and splitter 306 combines the
high-voltage DC inputs from all DC selector and converter 301, 302,
. . . , 304 and then outputs the total high-voltage DC power to the
DC-AC inverter 308. It also combines the low-voltage DC inputs from
all DC selector and converter 301, 302, . . . , 304 and then
outputs the low-voltage DC power to (1) the internal DC power
supply 334, (2) battery charge controller 336, and (3) external DC
power supply 338. The internal DC power supply 334 then can supply
DC power to the internal electronics. The charge controller 336 can
take DC power from the DC power combiner & splitter 306 or from
the wind generator 298 directly to charge the battery set 296. The
external DC power supply 338 can supply DC power to one or multiple
DC loads through the DC output circuits 339. The detailed design
for the DC power combiner and splitter 306 and those to be
described in the embodiments herein will be disclosed in FIG.
16.
[0072] The combined high-voltage DC power enters the DC-AC inverter
308 and then is inverted into AC power. In the on-grid mode, the
inverted AC voltage is higher than the incoming AC voltage from the
grid. The generated AC power goes through the load interface
circuit 310 to be combined with the AC power in the internal AC
powerline 312. A line sensing circuit 318 connected to the internal
AC powerline 312 is used to detect the phase and zero-crossing
point of the incoming AC power from the power grid. The phase and
zero-crossing point signals are sent to the microcontroller 316 for
AC power synchronization to assure that the power inverter provides
high quality synchronized power to the grid. The line sensing
circuit 318 is also connected to the external AC powerline 330 to
detect the power grid status. In the off-grid mode, the inverted AC
voltage is regulated based on the rated off-grid output voltage of
the inverter.
[0073] The on-grid electric relay 314 controlled by the
microcontroller 316 is used to isolate the internal on-grid AC
powerline 312 from the external on-grid AC powerline 330. The
off-grid electric relay 328 controlled by the microcontroller 316
is used to isolate the internal off-grid AC powerline 326 from the
external off-grid AC powerline 332. The internal on-grid AC
powerline 312 and internal off-grid AC powerline 326 are connected.
However, the AC voltage on the internal powerline 312 and 326 is
dependent on whether the inverter is running in the on-grid or
off-grid mode. For instance, in the on-grid mode, the internal
powerline 312 is 240V, which matches the grid voltage in the U.S.
In the off-grid mode, the internal powerline 326 is 120V which is
the rated off-grid AC output voltage for the inverter to power 120V
AC loads.
[0074] During the on-grid mode, the on-grid electric relay 314 is
closed and off-grid electric relay 328 is open. The microcontroller
316 keeps detecting if there is grid power from the line sensing
circuit 318 connected to the internal on-grid AC powerline 312. If
there is grid power, it will continue to send power to the grid. As
soon as it detects the grid is down, it will stop generating power
within a fraction of a second based on the UL1741 requirement.
Then, the microcontroller sends a signal to disconnect the on-grid
electric relay 314. After waiting for a few seconds, the
microcontroller sends a signal to connect the off-grid electric
relay 328. The inverter then starts to send a test signal through
the internal off-grid powerline 326 and external off-grid powerline
332 to a connected off-grid AC circuit to check: (1) if there is AC
present in the off-grid circuit, and (2) if there is an AC load in
the off-grid circuit. If there is no AC present and an AC load is
detected, it will start to generate AC power to power the load.
Now, the inverter is working in the off-grid mode.
[0075] During the off-grid mode, the on-grid electric relay 314 is
open and off-grid electric relay 328 is closed. The microcontroller
316 is constantly detecting if there is grid power from the line
sensing circuit 318 connected to the external on-grid AC powerline
330. After grid power is detected, the inverter will wait for a few
minutes to assure the grid is stable. If the inverter is designed
to go back to the on-grid mode automatically, it will first stop
generating power to the off-grid circuit. After the microcontroller
assures that power generation is halted, it will send a signal to
disconnect the off-grid electric relay 328. Then, the
microcontroller sends a signal to connect the on-grid electric
relay 314. After a 5-minute mandatory waiting period, the inverter
starts to generate AC power to be sent to the power grid. Now, the
inverter is working in the on-grid mode. The on-grid electric
relays and off-grid electric relays to be described in FIG. 9 work
the same way as described here.
[0076] The load detector 324 as well as the ones to be described in
FIGS. 9, 11 and 12 are electronic circuits that can detect the
impedance of the connected AC load. If no AC power is detected on
the off-grid AC powerline, the load detector checks the impedance
of the off-grid AC powerline to determine if the connected AC load
is within certain specifications. The load detector in the
embodiments herein can be designed using standard LRC meter
impedance measurement circuits and mechanism such as those
described in the book, "The Measurement of Lumped Parameter
Impedance: A Metrology Guide" published by University of Michigan
Library in January 1974.
[0077] The powerline communications Modem 322 which is isolated by
an interface circuit 320 and the Modems to be described in FIGS.
10, 11, and 13 are used to establish a 2-way digital signal
communication between the microcontroller and the outside world
through the AC powerline. The Powerline Modem that can be used in
the embodiments herein can be any of a number of commercially
available integrated circuits capable of providing 2-way digital
communications through a powerline. Through the 2-way powerline
communication, the inverter can receive information such as power
dispatch commands from an independent grid system operator (ISO)
that manages power grids to ramp its output power up and down. With
flexible DC sources from solar, wind, and battery, the smart
renewable power generation system can help level the power peaks
and valleys to help stabilize the power grid.
[0078] The microcontroller 316 and the one to be described in FIG.
9 is used to perform a number of tasks including: (1) monitoring
the DC input voltage from solar, wind, and battery; (2) selecting
the DC sources based on the DC source selection criteria; (3)
monitoring the DC voltages in each of the DC selector and converter
circuits; (4) controlling the outputs of each of the DC selector
and converter circuits; (5) measuring the input voltage and
current, and calculating DC input power for each input channel; (6)
performing maximum power point tracking (MPPT) for each solar
panel; (7) performing DC-AC inversion, AC power synchronization,
and AC output current control; (8) monitoring AC current and
voltage for generated power amount and status; (9) performing
powerline or wireless communications; (10) performing logic
controls such as AC powerline switching and isolation; (11)
detecting the power grid status; (12) detecting off-grid AC circuit
status; (13) switching between on-grid and off-grid mode; and (14)
regulating AC output voltage when working in the off-grid mode.
[0079] The digital microcontroller 316 as well as those to be
described in FIGS. 9 to 14 are small computers on a single
integrated circuit (IC) or a set of ICs that consists of a central
processing unit (CPU) combined with functions and peripherals
including a crystal oscillator, timers, watchdog, serial and analog
I/Os, memory modules, pulse-width-modulation (PWM) generators, and
user software programs. A 32-bit high-performance floating-point
microcontroller is selected for this application. The digital
microcontroller in the embodiments herein performs real-time
control and optimization functions for the corresponding on-grid,
off-grid, and on/off-grid power inverters, in which Model-Free
Adaptive (MFA) controllers are used to control the DC converters
and inverter's AC outputs for on-grid, off-grid, and on/off-grid
applications. The MFA optimizers provide maximum power point
tracking (MPPT) to allow the power inverters to achieve optimal
power production. The MFA control and optimization technologies
have been described in U.S. Pat. Nos. 6,055,524, 6,556,980,
7,142,626, 7,152,052, 7,415,446 and 8,594,813, the contents of all
of which are hereby incorporated by reference.
[0080] FIG. 9 is a block diagram illustrating a m+1 channel
on/off-grid DC source flexible power inverter that is connected to
m solar panels and a battery set through corresponding DC input
channels, according to an embodiment of this invention.
[0081] The inverter comprises m DC selector and converter circuits
351, 352, . . . , 354, a DC power combiner and splitter 356, a
DC-AC inverter 358, a load interface circuit 360, an internal
on-grid AC powerline 362, an on-grid electric relay 364, a digital
microcontroller 366, a line sensing circuit 368, an antenna for
wireless communications 370, a wireless LAN (local area network)
module 372, a load detector 374, an internal off-grid AC powerline
376, an off-grid electric relay 378, an external on-grid AC
powerline 380 and 381, an external off-grid AC powerline 382, an
internal DC power supply 384, a 3-position manual switch 386, and a
charge controller 388. The external on-grid AC powerline 380 is
connected to an electric grid, and the external off-grid AC
powerline 382 is connected to an off-grid AC circuit. Notice that
this m+1 channel power inverter has a battery input channel but no
wind input channel.
[0082] The on-grid electric relay 364 controlled by the
microcontroller 366 is used to isolate the internal on-grid AC
powerline 362 from the external on-grid AC powerline 380. The
off-grid electric relay 378 controlled by the microcontroller 366
is used to isolate the internal off-grid AC powerline 376 from the
external off-grid AC powerline 382. The internal on-grid AC
powerline 362 and internal off-grid AC powerline 376 are connected.
However, the AC voltage on the internal powerline 362 and 376 is
dependent on whether the inverter is running in the on-grid or
off-grid mode.
[0083] The 3-position manual switch 386 is used to select the
inverter to work in the following positions: (1) auto position, (2)
on-grid position, and (3) off-grid position. In the auto position,
the microcontroller can switch between the on-grid and off-grid
mode based on the grid condition. In the on-grid position, the
inverter will work as an on-grid inverter. When the grid is down,
it will not switch to the off-grid mode. It must be switched to the
off-grid mode manually in order for the inverter to generate power
to the AC load. In the off-grid position, the inverter will work
like an off-grid inverter regardless of the power grid condition.
It must be switched to the on-grid mode manually in order for the
inverter to generate power to the grid.
[0084] The 3-position manual switch 386 is connected to the
microcontroller 366 through signal lines to inform the
microcontroller of the selected position. For example, the system
can be designed to use 0V, 2.5V, and 3.3V DC signals to switch
among the (1) auto position, (2) on-grid position, and (3) off-grid
position, respectively.
[0085] The DC selectors that can be used in the embodiments herein
are any of a number of electric devices to connect and disconnect
electric circuits including but not limited to electric relays,
contacts, and solid-state switches. The DC converters that can be
used in the embodiments herein are any of a number of well known
converters described in the "Power Electronics Handbook" edited by
Muhammad H. Rashid and published by Academic Press in 2007, the
entirety of which is hereby incorporated by reference, including
Buck Converter, Boost Converter, Buck-Boost Converter, Super-Lift
Luo Converter, and Cascade Boost Converter. The DC-AC inverters
that can be used in the embodiments herein are any of a number of
well known DC-AC inverters described in the "Power Electronics
Handbook" including Half-Bridge Inverter, Full-Bridge Inverter,
Bipolar PWM Inverter, Unipolar PWM Inverter, and Sinusoidal PWM
Inverter. The DC combiner used in the embodiments herein can be
designed with a circuit that allows the HV outputs and LV outputs
from all DC converters to connect in parallel, respectively, so
that all related DC currents are added together. The DC splitter
used in the embodiments herein can be designed to split and
distribute the DC power to the internal and external power supplies
as well as the charge controller.
[0086] The wireless LAN module that can be used in the embodiments
herein can be any of a number of commercially available integrated
circuits capable of providing 2-way digital communications through
wireless networks. Other modules discussed in the embodiments
herein including load interface, solid state switch, line sensing
circuit, powerline interface circuit, load detector, on-grid relay,
off-grid relay, internal DC power supply, external DC power supply,
and battery charge controller can be implemented using one or more
known combinations of conventional electronic components such as
resisters, capacitors, inductors, sensing circuits, solid-state
switches, transformers, diodes, transistors, operational
amplifiers, ceramic filters, and integrated circuits (ICs),
etc.
[0087] FIG. 10 is a block diagram illustrating a m+2 channel DC
source flexible on-grid power inverter that is connected to m solar
panels, a battery set, and a wind generator through corresponding
DC input channels, according to an embodiment of this
invention.
[0088] The inverter comprises m DC selector and converter circuits
401, 402, . . . , 404, a DC power combiner and splitter 406, a
DC-AC inverter 408, a load interface circuit 410, an internal
on-grid AC powerline 412, a solid state switch 414, a digital
microcontroller 416, a line sensing circuit 418, an interface
circuit for powerline communications 420, a powerline
communications Modem 422, an internal DC power supply 424, an
external AC powerline 426 and 427, and a charge controller 428.
[0089] During normal operating conditions, the power from solar
panels 391, 392, . . . , 394 is delivered to the corresponding DC
selector and converter 401, 402, . . . , 404 respectively. The
power from wind generator 398 can enter the DC selector and
converter 401, 402, . . . , 404 simultaneously as the wind
generator's DC output is connected to each of the converters in
parallel. The power from battery 396 can also enter the DC selector
and converter 401, 402, . . . , 404 simultaneously as its DC output
is connected to each of the converters in parallel.
[0090] Each DC selector and converter 401, 402, . . . , 404 is
controlled by the microcontroller 416 and can select one or more DC
sources from solar, wind, and battery depending on the DC selection
criteria. Each DC selector and converter can pull power from the
selected DC sources and combine the power. It then splits the DC
power into a high-voltage (HV) and a low-voltage (LV) output. These
2 outputs are connected to the DC power combiner and splitter
406.
[0091] The microcontroller 416 and the ones to be described in
FIGS. 13 and 14 is used to perform a number of tasks including: (1)
monitoring the DC input voltage from solar, wind, and battery; (2)
selecting the DC sources based on the DC source selection criteria;
(3) monitoring the DC voltages in each of the DC selector and
converter circuits; (4) controlling the outputs of each of the DC
selector and converter circuits; (5) measuring the input voltage
and current, and calculating DC input power for each input channel;
(6) performing maximum power point tracking (MPPT) for each solar
panel; (7) performing DC-AC inversion, AC power synchronization,
and AC output current control; (8) monitoring AC current and
voltage for generated power amount and status; (9) performing
powerline or wireless communications; and (10) performing logic
controls such as AC powerline switching and isolation.
[0092] The m-channel on-grid power inverters are disclosed in U.S.
Pat. No. 8,786,133 and subsequent patent applications. With more DC
sources from solar, wind, and battery, the on-grid power generation
system can be much more grid friendly. In fact, the system can be
used to provide grid stabilization services. Through the 2-way
communication via powerline or wireless LAN, the inverter can
receive power dispatch commands from an independent grid system
operator (ISO) that manages power grids to ramp its output power up
and down. With flexible DC sources from solar, wind, and battery,
the smart renewable power generation system can help level the
power peaks and valleys to help stabilize the power grid.
[0093] As an example, the m+2 channel on-grid DC flexible power
inverter can be designed based on the following criteria: (1) If
there is sufficient solar, pull less power from the wind generator
to reduce the wear and tear since it has moving parts; (2) If there
is sufficient solar and/or wind power, do not pull power from the
battery; (3) charge the battery if there is sufficient wind power
which enters the charge controller directly; (4) maximize AC power
production if the grid needs power; (5) reduce or stop AC power
production if the grid does not allow AC power injection; (6)
charge battery if there is excess power from the wind and/or solar,
while sending AC power to the grid; (7) if battery is fully charged
and grid does not allow AC power injection, generate AC power for
the local loads only or simply postpone power production; and (8)
use battery to supply DC power to the internal DC power supply to
keep the inverter running when there is no sunlight so that the
inverter can be ready to pull DC power from the wind generator for
AC power production when there is sufficient wind speed.
[0094] FIG. 10 illustrates that the same external AC powerline can
have 2 pairs of AC wires 426 and 427 connected in parallel to
facilitate AC input and output ports for daisy-chaining multiple
inverters. That is, the AC output port of an inverter connects to
the AC input port of the next inverter, and so on. Although we say
the inverters daisy chain, the actual connection of the inverter's
AC powerline is in parallel or pass-through. In FIG. 10, the
solid-state relay 414, external AC powerline 426, and their
supporting circuits can form an AC output port. The solid-state
relay 414, external AC powerline 427, and their supporting circuits
can form an AC input port. In physical design of an on-grid power
inverter, the AC input port and AC output port can be constructed
by using appropriate AC wires and connectors to make the
installation user-friendly. For instance, the AC output port can
use a male-type AC connector and the AC input port can use a
female-type AC connector, making a matching pair. This way, the
user can easily make the AC connections and avoid potential errors.
The drawings of the external AC powerline 380 and 381 in FIGS. 9
and 426 and 427 in FIG. 10 show the concept of how multiple
inverters can daisy-chain as illustrated in FIGS. 6 and 7.
[0095] FIG. 11 is a block diagram illustrating a m+2 channel DC
source flexible off-grid power inverter that is connected to m
solar panels, a battery set, and a wind generator through
corresponding DC input channels, according to an embodiment of this
invention.
[0096] The inverter comprises m DC selector and converter circuits
441, 442, . . . , 444, a DC power combiner and splitter 446, a
DC-AC inverter 448, a load interface circuit 450, an internal
off-grid AC powerline 452, a load detector 454, a digital
microcontroller 456, a line sensing circuit 458, an interface
circuit for powerline communications 460, a powerline
communications Modem 462, an internal DC power supply 464, an
external off-grid AC powerline 466, a charge controller 468, an
external DC power supply 469, and DC output circuits 470.
[0097] During normal operating conditions, the power from solar
panels 431, 432, . . . , 434 is delivered to the corresponding DC
selector and converter 441, 442, . . . , 444 respectively. The
power from wind generator 438 can enter the DC selector and
converter 441, 442, . . . , 444 simultaneously as the wind
generator's DC output is connected to each of the converters in
parallel. The power from battery 436 can also enter the DC selector
and converter 441, 442, . . . , 444 simultaneously as its DC output
is connected to each of the converters in parallel.
[0098] Each DC selector and converter 441, 442, . . . , 444 is
controlled by the microcontroller 456 and can select one or more DC
sources from solar, wind, and battery depending on the DC selection
criteria. DC selector and converter can pull power from the
selected DC sources and combine the power. It then splits the DC
power into a high-voltage (HV) and a low-voltage (LV) output. These
2 outputs are connected to the DC power combiner and splitter
446.
[0099] The microcontroller 456 and the one to be described in FIG.
12 is used to perform a number of tasks including: (1) monitoring
the DC input voltage from solar, wind, and battery; (2) selecting
the DC sources based on the DC source selection criteria; (3)
monitoring the DC voltages in each of the DC selector and converter
circuits; (4) controlling the outputs of each of the DC selector
and converter circuits; (5) measuring the input voltage and
current, and calculating DC input power for each input channel; (6)
performing maximum power point tracking (MPPT) for each solar
panel; (7) performing DC-AC inversion, AC power synchronization,
and AC output current control; (8) monitoring AC current and
voltage for generated power amount and status; (9) performing
powerline or wireless communications; (10) performing logic
controls such as AC powerline switching and isolation; (11)
detecting off-grid AC circuit status; and (12) regulating AC output
voltage.
[0100] Since this is an off-grid DC source flexible power inverter
that has both AC and DC outputs to run connected AC and DC loads,
the DC selection and power pulling criteria should be different
than the on-grid power inverter. For instance, an off-grid DC
source flexible power inverter can be designed to include the
following functions: (1) pull all available DC power from the wind
generator and use only a portion of the solar energy needed to run
the AC and DC loads, since it is easier to pull more or less power
from solar panels to achieve rapid load balancing; (2) if
additional DC power is needed to run the AC and DC loads, pull
power from the solar panels; (3) if required, pull all available DC
power from all solar panels at its maximum power point (MPP); (4)
when the sun and wind cannot supply sufficient DC power for the
inverter to run the AC and DC loads, pull power from the battery
set; (5) charge the battery if there is excess DC power from the
solar panels and/or wind generator; (6) charge the battery using DC
power directly from the wind generator; and (7) when sufficient DC
power is available from solar panels and wind generator, gradually
stop pulling power from the battery set.
[0101] For product implementation, the inverters in the embodiments
herein can be designed to include the following capabilities: (1)
be able to select and pull power from available DC sources based on
certain criteria; (2) be able to combine all available DC power
from solar, wind, and battery to meet the production demand to run
the connected AC and DC loads; (3) be able to charge batteries
using wind power directly so that battery charging does not affect
the inverter operations and its maximum power capacity; and (4)
implement the DC source selection criteria in computer software,
which is configurable to achieve desirable functions for a specific
application.
[0102] The function of regulating AC output voltage for the
off-grid DC source flexible power inverter is achieved by the
digital microcontroller with its supporting circuits and software
to perform the following: (1) measuring the AC output voltage in
real-time; (2) comparing it with the rated AC output voltage
setpoint such as 120V; and (3) adjusting the AC output current or
output power until the output voltage is regulated around its
setpoint within a specified deadband. More specifically, if the AC
output voltage is higher than its setpoint, the microcontroller
will reduce the output current by decreasing the duty-cycle of the
pulse-width-modulation (PWM) of the DC converter. If the AC output
voltage is lower than its setpoint, it will increase the duty-cycle
of PWM to increase the AC output current. If the AC output voltage
is within the deadband of its setpoint such as 120V+/-1V, the
microcontroller will not make PWM duty-cycle adjustments to keep
the AC output current and AC output power stable. Based on the
Ohm's Law, the AC output voltage is in proportion of the AC output
current so that it can be regulated accordingly. The function of
regulating AC output voltage for the on/off-grid power inverter in
its off-grid mode described in FIGS. 8 and 9 works the same
way.
[0103] Since the disclosed DC source flexible power inverters are
used for solar and wind power applications, the available DC input
power from each input channel will vary due to sunlight and wind
speed variations. On the other hand, the total AC loads may change
quickly and frequently. The automatic control system to regulate
the inverter's output voltage for off-grid applications can be
difficult to implement. The Model-Free Adaptive (MFA) controllers
described in U.S. Pat. Nos. 6,055,524, 6,556,980, 7,142,626,
7,152,052, 7,415,446 and 8,594,813, the contents of all of which
are hereby incorporated by reference, are implemented in the
microcontroller to achieve robust control performance for AC output
voltage regulation.
[0104] In the embodiments herein, the function of regulating DC
output voltages for the external power supply is achieved by the
microcontroller with its supporting circuits and software. The
useful DC outputs may include the following: (1) 5V DC for small
devices and phone chargers, (2) 12V DC for shop tools, and (3) 24V
DC for instruments.
[0105] FIG. 12 is a block diagram illustrating a m+1 channel
off-grid DC source flexible power inverter that is connected to m
solar panels and a battery set through corresponding DC input
channels, according to an embodiment of this invention.
[0106] The inverter comprises m DC selector and converter circuits
481, 482, . . . , 484, a DC power combiner and splitter 486, a
DC-AC inverter 488, a load interface circuit 490, an internal
off-grid AC powerline 492, a load detector 494, a digital
microcontroller 496, a line sensing circuit 498, an antenna for
wireless communications 500, a wireless LAN module 502, an internal
DC power supply 504, an external off-grid AC powerline 506 and 507,
a charge controller 508, an external DC power supply 509, and DC
output circuits 510.
[0107] During normal operating conditions, the power from solar
panels 471, 472, . . . , 474 is delivered to the corresponding DC
selector and converter 481, 482, . . . , 484 respectively. The
power from battery 476 can enter the DC selector and converter 481,
482, . . . , 484 simultaneously as its DC output is connected to
each of the converters in parallel. Each DC selector and converter
481, 482, . . . , 484 is controlled by the microcontroller 496 and
can select one or more DC sources from solar and battery depending
on the DC selection criteria. Each DC selector and converter can
pull power from the selected DC sources and combine the power. It
then splits the DC power into a high-voltage (HV) and a low-voltage
(LV) output. These 2 outputs are connected to the DC power combiner
and splitter 486.
[0108] This is an off-grid DC source flexible power inverter that
has both AC and DC outputs to run connected AC and DC loads, yet it
has only solar and battery as DC sources. As an example, it can be
designed to include the following functions: (1) If required, pull
all available DC power from all solar panels at its maximum power
point (MPP); (2) when the sun cannot supply sufficient DC power for
the inverter to run the AC and DC loads, pull power from the
battery; (3) charge the battery if there is excess DC power from
the solar panels; and (4) when sufficient DC power is available
from solar panels, gradually stop pulling power from the
battery.
[0109] Compared with the m+2 channel off-grid inverter in FIG. 11,
the m+1 channel off-grid inverter in FIG. 12 does not include a
wind input channel, but works similarly. Another difference is that
the inverter in FIG. 11 has powerline communications, and the
inverter in FIG. 12 has wireless communications.
[0110] FIG. 12 also illustrates that the same external off-grid AC
powerline can have 2 pairs of AC wires 506 and 507 connected in
parallel to facilitate AC input and output ports for daisy-chaining
multiple off-grid power inverters. The smart and scalable off-grid
power inverters have been described in the U.S. patent application
Ser. No. 13/493,622, where multiple off-grid inverters can work
together as a group, in which an AC master inverter is the "leading
inverter" to generate AC power to the off-grid AC powerline to
allow the other off-grid inverters connected to the same AC
powerline to synchronize with the AC power being produced by the AC
master inverter.
[0111] FIG. 13 is a block diagram illustrating a m+1 channel DC
source flexible on-grid power inverter that is connected to m solar
panels and a battery set through corresponding DC input channels,
according to an embodiment of this invention.
[0112] The inverter comprises m DC selector and converter circuits
521, 522, . . . , 524, a DC power combiner and splitter 526, a
DC-AC inverter 528, a load interface circuit 530, an internal
on-grid AC powerline 532, a solid state switch 534, a digital
microcontroller 536, a line sensing circuit 538, an interface
circuit for powerline communications 540, a powerline
communications Modem 541, an antenna for wireless communications
542, a wireless LAN module 543, an internal DC power supply 544, an
external on-grid AC powerline 546, and a charge controller 548.
[0113] During normal operating conditions, the power from solar
panels 511, 512, . . . , 514 is delivered to the corresponding DC
selector and converter 521, 522, . . . , 524 respectively. The
power from battery 516 can enter the DC selector and converter 521,
522, . . . , 524 simultaneously as its DC output is connected to
each of the converters in parallel. Each DC selector and converter
521, 522, . . . , 524 is controlled by the microcontroller 536 and
can select one or more DC sources from solar and battery depending
on the DC selection criteria. Each DC selector and converter can
pull power from the selected DC sources and combine the power. It
then splits the DC power into a high-voltage (HV) and a low-voltage
(LV) output. These 2 outputs are connected to the DC power combiner
and splitter 526.
[0114] Compared with the m+2 channel off-grid inverter in FIG. 10,
the m+1 channel off-grid inverter in FIG. 13 does not include a
wind input channel, but works similarly. Another difference is that
the inverter in FIG. 10 has powerline communications, and the
inverter in FIG. 13 has both powerline and wireless communications.
Since this is an on-grid solar power system with energy storage
batteries, it is well suited to provide grid power stabilization
services.
[0115] FIG. 14 is a block diagram illustrating a m+1 channel DC
source flexible on-grid power inverter that is connected to m solar
panels and a wind generator through corresponding DC input
channels, according to an embodiment of this invention.
[0116] The inverter comprises m DC selector and converter circuits
561, 562, . . . , 564, a DC power combiner and splitter 566, a
DC-AC inverter 568, a load interface circuit 570, an internal
on-grid AC powerline 572, a solid state switch 574, a digital
microcontroller 576, a line sensing circuit 578, an antenna for
wireless communications 580, a wireless LAN module 582, an internal
DC power supply 584, and an external on-grid AC powerline 586.
[0117] During normal operating conditions, the power from solar
panels 551, 552, . . . , 554 is delivered to the corresponding DC
selector and converter 561, 562, . . . , 564 respectively. The
power from a wind generator 558 can enter the DC selector and
converter 561, 562, . . . , 564 simultaneously as its DC output is
connected to each of the converters in parallel. Each DC selector
and converter 561, 562, . . . , 564 is controlled by the
microcontroller 576 and can select one or more DC sources from
solar and wind generator depending on the DC selection criteria.
Each DC selector and converter can pull power from the selected DC
sources and combine the power. It then splits the DC power into a
high-voltage (HV) and a low-voltage (LV) output. These 2 outputs
are connected to the DC power combiner and splitter 566.
[0118] This m+1 channel on-grid inverter works similarly to the
on-grid inverters described in FIGS. 10 and 13. However, since it
does not include batteries, the system is relatively simple. The DC
source selection criteria can be designed based on the objective to
reduce wear and tear for the wind generator in the following: (1)
pull all available DC power from all solar panels at its maximum
power point (MPP); (2) supply additional DC power from the wind
generator to allow the inverter to work at its peak AC power
generation state; and (3) in low irradiance conditions, stop
pulling power from the solar panels so that the DC from solar
panels is able to supply sufficient DC power for the internal
electronics to keep the inverter running, and then pull power from
the wind generator when it has sufficient wind speed and produce AC
to be sent to the grid.
[0119] A method and apparatus for maximizing power production for
solar power systems when there is low sunlight is disclosed in the
U.S. patent application Ser. No. 13/789,637. A multiple-channel
solar power inverter can work in a low power mode when there is low
sunlight. The inverter dedicates one solar panel to supply DC power
to keep the inverter running allowing the inverter to pull power
from other solar panels for AC power generation. The described m+1
channel on-grid power inverter can work well in this situation.
Since wind is random and the wind speed can reduce to zero
frequently, keeping the power inverter running can significantly
improve the harvest of wind energy. Based on the UL1741 standard,
an on-grid solar or wind inverter is required to wait 5 minutes
before it can send power to the grid. When the wind speed goes to
zero, an inverter with only a wind generator as DC source will be
forced to shutdown. When there is sufficient wind, it will still
have to wait for 5-minutes, causing power generation loss. For this
reason, the multi-channel DC flexible power inverters disclosed in
this patent can also be useful for large wind generators by adding
solar panels and batteries to keep the power inverter running
regardless of the wind speed.
[0120] FIG. 15 is a block diagram illustrating a DC selector and
converter mechanism, according to an embodiment of this invention.
It details the design for each DC selector and converter
illustrated in FIGS. 8 to 14.
[0121] The DC selector and converter mechanism 600 comprises a
sensing & selection circuit 602 that takes DC power from a wind
generator, a sensing & selection circuit 604 that takes DC
power from a solar panel, a sensing & selection circuit 606
that takes DC power from a battery set 614, a DC source combiner
608 that combines the DC power from all sensing & selection
circuits, and a DC-DC boost converter that can boost the input DC
voltage to a higher output voltage. The DC source combiner has 2
outputs, one of which enters the DC-DC boost converter 618, and the
other is the low-voltage (LV) output. The DC-DC boost converter
provides the high-voltage (HV) output for the DC selector and
converter mechanism 600.
[0122] During normal operating conditions, the power from the wind
generator 610, solar panel 612, and battery set 614 can enter the
DC selector and converter mechanism 600 individually or
simultaneously depending on the DC source selection and power
pulling criteria implemented in the software in the digital
microcontroller 616.
[0123] FIG. 16 is a block diagram illustrating a portion of a m+2
channel DC source flexible power inverter with more detailed
illustration for a DC power combiner and splitter mechanism,
according to an embodiment of this invention. The DC power combiner
and splitter mechanism 660 in FIG. 16 details the design for the DC
power combiner and splitter illustrated in FIGS. 8 to 14.
[0124] In FIG. 16, the m+2 channel DC source flexible power
inverter shows that it comprises m DC selector and converter
circuits 651, 652, . . . , 654, a DC power combiner and splitter
660, a digital microcontroller 664, a DC-AC inverter 666, an
external DC power supply 668, an internal DC power supply 670, and
a charge controller 672. The DC power combiner and splitter 660
further comprises a high-voltage (HV) combiner 656, and low-voltage
(LV) combiner 658, and a voltage splitter 662.
[0125] During normal operating conditions, the power from solar
panels 641, 642, . . . , 644 is delivered to the corresponding DC
selector and converter 651, 652, . . . , 654 respectively. The
power from wind generator 648 can enter the DC selector and
converter 651, 652, . . . , 654 simultaneously as the wind
generator's DC output is connected to each of the converters in
parallel. The power from the battery set 646 can also enter the DC
selector and converter 651, 652, . . . , 654 simultaneously as its
DC output is connected to each of the converters in parallel. The
HV and LV outputs from each DC selector and converter 651, 652, . .
. , 654 enter the high-voltage (HV) combiner 656 and low-voltage
(LV) combiner 658, respectively. The high-voltage (HV) combiner 656
combines all high-voltage DC inputs and supplies the resulting DC
to the DC-AC inverter 666 to produce high voltage AC power. The
low-voltage (LV) combiner 658 combines all low-voltage DC inputs
and supplies the resulting DC to the voltage splitter 662. Based on
the requirements from the external DC power supply 668, internal DC
power supply 670, and battery charge controller 672, the voltage
splitter 662 can supply the corresponding DC power with the
appropriate voltage and current.
[0126] FIG. 17 is a block diagram illustrating a battery charge
controller with one or multiple DC inputs, according to an
embodiment of this invention. The charge controller 680 in FIG. 17
details the design for the charge controller illustrated in FIGS. 8
to 14. It comprises a DC selector 682 that can take DC power from
the wind generator 292, and a DC selector 684 that can take DC
power from the low-voltage DC output of the DC power combiner and
splitter 694. The selected DC power enters the battery charger 686
to charge the battery 696. The DC selectors 682, 684 and the
battery charger are controlled by the microcontroller 690 for DC
selection and battery charging operations.
[0127] In the embodiments herein, the DC selector and combiner
mechanism, the DC power combiner and splitter, as well as the
battery charge controller can be implemented using one or more
known combinations of conventional electronic components such as
resisters, capacitors, inductors, sensing circuits, solid-state
switches, transformers, diodes, transistors, operational
amplifiers, ceramic filters and integrated circuits (ICs), etc.
[0128] The applying organization of this patent has built
commercial 4-channel on-grid power inverters for on-grid
applications, 4-channel off-grid power inverters for off-grid
applications, and 4-channel on/off-grid power inverters for
applications where grid power is not stable. The described grid and
DC source flexible power generation systems and supporting on-grid,
off-grid, and on/off-grid DC source flexible power inverters take
the unique design and concept of multi-channel power inverters to
the next level.
[0129] Since both AC and DC are flexible in this design, the
possible number of combinations of AC and DC outputs as well as DC
sources is large. The following table summarizes the possible power
inverter configurations. For instance, the m+2 channel on/off-grid
DC flexible power inverter described in FIG. 2 has solar, wind, and
battery DC sources, and can produce AC power to the grid or an
off-grid circuit, and can also charge the connected battery. So, it
is type 11d in the table.
TABLE-US-00001 Inputs--DC Source c d a b Solar + Solar + Wind + No
Outputs Solar Solar + Wind Battery Battery 1 On-Grid AC Yes Yes Yes
Yes 2 On-Grid AC Yes Yes Yes Yes with DC Output 3 On-Grid AC No No
Yes Yes with Battery Charging 4 On-Grid AC No No Yes Yes with DC
Output and Battery Charging 5 Off-Grid AC Yes Yes Yes Yes 6
Off-Grid AC Yes Yes Yes Yes with DC Output 7 Off-Grid AC No No Yes
Yes with Battery Charging 8 Off-Grid AC No No Yes Yes with DC
Output and Battery Charging 9 On/Off-Grid AC Yes Yes Yes Yes 10
On/Off-Grid AC Yes Yes Yes Yes with DC Output 11 On/Off-Grid AC No
No Yes Yes with Battery Charging 12 On/Off-Grid AC No No Yes Yes
with DC Output and Battery Charging
[0130] The table shows 36 types of possible combinations. In
addition, more design variations may include the following: (1)
daisy-chained and/or combined parallel AC connections among the
inverters, (2) the number and different types of inverters
connected to form a group, (3) powerline and/or wireless
communications, (4) supported size and voltage range of solar
panels, wind generators, and batteries, (5) AC voltage and
frequency of the AC output power based on specific electric
standard, and (6) voltages and power that the external DC power
supply can support.
[0131] Although the possible variations of the flexible power
inverter design are many, the actual implementation of commercial
products can be done using standard electronic components, cables,
connectors, hardware jumpers or switches, and computer software
making the configuration user-friendly. This design demonstrates
the innovation of delivering flexible, cost-effective, and
user-friendly power generation systems to harvest any form of
renewable energy available and convert it to usable electricity for
everyone but especially for those people in need.
* * * * *