U.S. patent application number 10/667219 was filed with the patent office on 2004-05-27 for dc power system for marine vessels.
Invention is credited to Cratty, William E., Fairfax, Stephen A..
Application Number | 20040102109 10/667219 |
Document ID | / |
Family ID | 32312457 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040102109 |
Kind Code |
A1 |
Cratty, William E. ; et
al. |
May 27, 2004 |
DC power system for marine vessels
Abstract
An embodiment of the invention is a power system for a marine
vessel including a plurality of power sources. A propulsion power
distribution unit is coupled to the plurality of primary power
sources. A plurality of propulsion devices are coupled to the
propulsion power distribution unit. A weaponry power distribution
unit is coupled to the propulsion power distribution unit. A
plurality of directed energy weapons are coupled to the weaponry
power distribution unit.
Inventors: |
Cratty, William E.; (Bethel,
CT) ; Fairfax, Stephen A.; (Lincoln, MA) |
Correspondence
Address: |
CANTOR COLBURN LLP
55 Griffin Road South
Bloomfield
CT
06002
US
|
Family ID: |
32312457 |
Appl. No.: |
10/667219 |
Filed: |
September 18, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60411660 |
Sep 18, 2002 |
|
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|
Current U.S.
Class: |
440/113 |
Current CPC
Class: |
B63H 21/17 20130101;
H02J 1/08 20130101; H02J 1/06 20130101; H02J 2310/42 20200101; Y02T
90/38 20130101; H02J 1/16 20130101; H02J 1/10 20130101; B63H 23/24
20130101; B63J 3/02 20130101; B63J 2003/002 20130101; Y02T 90/40
20130101 |
Class at
Publication: |
440/113 |
International
Class: |
B63H 019/00 |
Claims
What is claimed:
1. A power system for a marine vessel, the power system comprising:
a plurality of primary power sources; a propulsion power
distribution unit coupled to said plurality of primary power
sources, a plurality of propulsion devices coupled to said
propulsion power distribution unit, said propulsion devices
imparting motion to said vessel; a weaponry power distribution unit
coupled to said propulsion power distribution unit; a plurality of
directed energy weapons coupled to said weaponry power distribution
unit.
2. The power system of claim 1 wherein: said propulsion power
distribution unit is a DC power distribution unit and includes two
rails connected by a plurality of propulsion rungs.
3. The power system of claim 2 wherein: each of said primary power
sources is coupled to one of said plurality of propulsion
rungs.
4. The power system of claim 2 wherein: each of said primary power
sources is coupled to each of said plurality of propulsion rungs
through an AC-DC converter.
5. The power system of claim 2 wherein: each of said plurality of
propulsion rungs is coupled to a respective propulsion device.
6. The power system of claim 2 wherein: said weaponry power
distribution unit is a DC power distribution unit including two
rails connected by a plurality of weaponry rungs.
7. The power system of claim 6 wherein: each of said propulsion
rungs is coupled to one of said plurality of weaponry rungs.
8. The power system of claim 7 wherein: each of said propulsion
rungs is coupled to one of said plurality of weaponry rungs through
a DC-DC converter.
9. The power system of claim 6 wherein: each of said plurality of
weaponry rungs is coupled to a respective directed energy
weapon.
10. The power system of claim 2 further comprising: an auxiliary
power distribution unit coupled to said propulsion power
distribution unit.
11. The power system of claim 10 wherein: said auxiliary power
distribution unit is a DC power distribution unit including two
rails connected by a plurality of auxiliary rungs.
12. The power system of claim 11 wherein: each of said propulsion
rungs is coupled to one of said plurality of auxiliary rungs.
13. The power system of claim 12 wherein: each of said propulsion
rungs is coupled to one of said plurality of auxiliary rungs
through a DC-DC converter.
14. The power system of claim 11 wherein: each of said plurality of
auxiliary rungs is coupled to a respective auxiliary load.
15. The power system of claim 11 further comprising: an ancillary
power source coupled to at least one of said auxiliary rungs.
16. The power system of claim 15 wherein: said ancillary power
source is a flywheel.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application serial No. 60/411,660 filed Sep. 18, 2002, the
entire contents of which are incorporated herein by reference.
BACKGROUND
[0002] The invention relates to DC power systems and is related to
U.S. patent application Ser. No. 09/870,897, the entire contents of
which are incorporated herein by reference, U.S. patent application
Ser. No. 10/186,768, the entire contents of which are incorporated
herein by reference, U.S. patent application Ser. No. 10/231,330,
the entire contents of which are incorporated herein by reference
and U.S. provisional patent application serial No. 60/385,685, the
entire contents of which are incorporated herein by reference.
[0003] The electric service on marine vessels typically comprises
two or more diesel powered generators paralleled together on a
common AC electric bus. While there is a great body of experience
with conventional power plants in marine service, maintaining
stability of an AC system is quite complex; all generators must
remain in phase. AC generator stability issues include hunting,
maximum power--pullout angle, effects of faults, out-of-phase
transfers, and load transients. For best effect, generating sources
must be independent; AC generators in synchronization are not
independent. Also, reactive AC, or the out-of-phase portion of the
AC wave, does no useful work. Inherent to conventional marine power
plants is the pervasiveness of reactive power that can reduce
resulting voltage, heat equipment and wires, and waste energy.
SUMMARY OF THE INVENTION
[0004] An embodiment of the invention is a power system for a
marine vessel including a plurality of power sources. A propulsion
power distribution unit is coupled to the plurality of primary
power sources. A plurality of propulsion devices are coupled to the
propulsion power distribution unit. A weaponry power distribution
unit is coupled to the propulsion power distribution unit. A
plurality of directed energy weapons are coupled to the weaponry
power distribution unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIGS. 1A and 1B depict a power system in one embodiment of
the invention.
DETAILED DESCRIPTION
[0006] FIGS. 1A and 1B depict a power system in an embodiment of
the invention. The power system provides high availability
(24.times.7.times.forever); computer grade electricity to land
based mission critical business and industrial processes. The
system may be adapted for use on naval vessels to provide an
electric infrastructure that greatly improves overall performance,
reliability, and survivability.
[0007] The power system uses a redundant array of independent
devices ("RAID") architecture, to integrate multiple, independent,
on-site power generators of any type (e.g., fuel cells, gas
reciprocating engines, gas turbines, etc.), rotary power
conditioners (motor generators), and flywheels by means of a water
cooled DC link to create an ultra reliable, computer grade power
system. The power system technology includes rectifier topology,
failsafe controls, a DC disconnect capable of interrupting 6 k amps
without arcing, and a unique over voltage protection device. The
power system has no single point of failure and is extremely fault
tolerant. The science of probabilistic risk assessment ("PRA")
determines the number of redundant components in a specific
installation. The design balances redundancy against the inherent
problem of complexity to arrive at an optimal and simple system
design.
[0008] Referring to FIG. 1A, primary power sources 20 generate AC
power that feeds a propulsion power distribution unit. Primary
power sources 20 may be any known power source such as fuel cells,
gas reciprocating engines, gas turbines, etc. The propulsion power
distribution unit includes two DC rails 22 and 24 coupled by rungs
26A, 26B and 26C. Each rung 26 is fed power by each of the primary
power sources 20 through AC-DC converters 28. The power system
takes the AC output of each primary power source 20 into separate,
independent rectifiers and changes the power to DC that supplies
the dual rail, DC propulsion power distribution unit. Voltage on
the DC link system is tightly controlled (e.g., to 550 volts). Each
rung 26 is coupled to a propulsion motor 30 which imparts motion to
the vessel. Within each rung 26, disconnects 32 straddle feeds in
and out of the rung 26. This allows components or even an entire
rung 26 to be isolated for service, upgrade, etc.
[0009] Using a DC propulsion power distribution unit eliminates the
issues of paralleling AC outputs from multiple generating sources,
takes away the possibility of single points of failure, and
eliminates inter-dependencies among generation sources, negating
the potential for cascade failures. Reverse power flow may be
blocked by diodes; low voltage or phasing on one generating source
cannot affect others. The DC propulsion power distribution unit
allows independent control of real power from each source thereby
eliminating reactive power issues at the generator.
[0010] The DC propulsion power distribution unit provides DC power
to a weaponry power distribution unit. The weaponry power
distribution unit includes two DC rails 42 and 44 coupled by rungs
46A, 46B and 46C. Each rung 46 is fed power by one of rungs 26A-26C
through DC-DC converters 48. Each rung 46 is coupled to directed
energy weaponry 50. Within each rung 46, disconnects 52 straddle
feeds in and out of the rung 46. This allows components or even an
entire rung 46 to be isolated for service, upgrade, etc. An energy
storage device 54, such as a superconducting magnetic energy
storage device, is coupled to each rung 46.
[0011] The DC propulsion power distribution unit is also connected
to an auxiliary power distribution unit shown in FIG. 1B. The
auxiliary power distribution unit includes two DC rails 62 and 64
coupled by rungs 66A-66G. Rung 26B is coupled to rung 66B through
DC-DC converter 68A. Rung 26A is coupled to rung 66D through DC-DC
converter 68B. Rung 26C is coupled to rung 66F through DC-DC
converter 68C. Each rung 66 also receives power from multiple
auxiliary power sources 70 which generate AC power and are coupled
to one or more rungs 66 though AC-DC converters 72. Auxiliary power
sources 70 may be any known power source (e.g., fuel cells, gas
reciprocating engines, gas turbines, etc.). AC loads 74 may be
connected to each rung through DC-AC converters 76 (e.g.,
motor-generators). DC-AC converter 76 output may be 480 VAC with
the voltage tolerance parameters that IEEE Standard 446-1987
specifies for computer equipment. The DC-AC converter 76 clears
faults and handles inrush current demands from the loads. The DC-AC
converters 76 also supplies reactive power close to the load
allowing the prime generating sources to operate at a high power
factor. Solid state variable speed drives may be used to convert
the 550 VDC to 480 VAC for powering chillers, fans, and pumps.
[0012] DC loads 78 may be connected to each rung through DC-DC
converters 80. DC-DC converter 80 may be employed to buck the DC
link voltage to 48 VDC at the point of use for telecom loads.
[0013] Within each rung 66, disconnects 82 straddle feeds in and
out of the rung 66. This allows components or even an entire rung
66 to be isolated for service, upgrade, etc. Ancillary power
sources 84 (e.g., flywheels, batteries) are coupled to one or more
rungs 66 to stabilize system voltage and mitigate the effects of
faults, generating source failures, and load transients.
[0014] Each load, whether DC or AC, is isolated from other system
outputs by AC-DC converter or DC-DC converter. Therefore, an
electrical event on one circuit cannot propagate to any other
circuit.
[0015] While at sea in non-combat conditions, in addition to
powering the main propulsion motors 30 via the 20 kVDC propulsion
power distribution unit, the primary power sources 20 supply power
to the 600 VDC auxiliary power distribution unit and the weapon
power distribution unit. During battle conditions the auxiliary
power sources 70 would be brought on line so that all of the power
from the primary power sources would be available to the main
propulsion motors 30 and directed energy weaponry 50.
[0016] The energy storage device 54 supplies high intensity power
bursts to the directed energy weapons 50, which could be
high-energy microwave or laser based weapons. Energy storage device
54 may be charged using regenerative braking techniques. While in
port, the primary power sources 20 are shut down and an appropriate
number of auxiliary power sources 70 supply power requirements. The
number of primary power sources 20 and auxiliary power sources 70
depends upon the redundancy needed to achieve the desired level of
availability.
[0017] The power system of FIGS. 1A and 1B allow compact power
sources such as rotary engines to be used for the auxiliary power
sources 70. The auxiliary power sources 70 as well as the primary
power sources 20 may be disbursed strategically throughout the
ship. This enhances survivability; power would be available to both
parts even if the ship were to be cut completely in two. In an
emergency, the system can be configured so that the main propulsion
motors 30 are powered from the auxiliary power distribution unit,
albeit at a reduced power rating. By using the DC systems described
herein, ship designers realize significant space and weight savings
in a vessel's electric infrastructure while effecting a substantial
improvement in reliability, availability, and survivability.
[0018] The power system does not subscribe to an "N+2" or similar
simplistic redundancy criteria. The power system is designed to
meet specific availability and reliability requirements, and to
eliminate single points of failure. Redundant units are added as
required based on the PRA evaluation. Units that fail more
frequently (e.g., engine generators) will require a larger degree
of redundancy than more reliable components (e.g., motor
generators). Simplistic "N+1" or "2N" redundancy criteria typically
spend far too much on some redundant systems while simultaneously
providing too little redundancy for others. The result is a
needlessly complex system that costs more, is difficult to operate
and maintain, and as a result is more likely to fail. In
embodiments of the power system, redundancy is balanced against the
inherent problem of complexity to arrive at a system design that
meets system requirements at a minimum cost. The quantitative
approach to this area results in the user being able to make
informed decisions about redundancy, spare parts inventory,
operating tactics, service agreements, and staffing levels.
[0019] The propulsion power distribution units may be implemented
using a superconducting DC bus operating at .+-.10 kV and up to 10
kA. This bus is suitable for conveying power from multiple remote
sources to the ship's drive systems and to the various directed
energy weapons 50 and energy storage device 54. The bus design
includes cooling and thermal management systems. Emphasis may be
placed on making the bus small, rugged, and requiring extremely
little or no maintenance throughout its operating lifetime.
[0020] Rectifiers and inverters employed in AC-DC converters, DC-AC
converters and DC-DC converters in the power system may use SCR
technology because of the technology's proven field reliability and
extraordinary ruggedness. The power system may use water cooling to
minimize module size and weight. Cryogenic cooling (typically with
liquid nitrogen, to 77 degrees Kelvin) offers several potential
advantages for DD(X) applications. First, cryogenic cooling reduces
resistive losses in copper components by a factor of six, resulting
in improved efficiency at the high drive power levels, and/or
substantially reduced footprint by virtue of greatly reduced
electrical interconnect size.
[0021] Second, cryocooling offers the potential of allowing the
SCRs to handle extremely large momentary overloads, as the maximum
junction temperature limits will remain unchanged at approximately
400 Kelvin. When cooled at or near room temperature, junction
temperature rise during an electrical fault or pulsed power
operation (for firing directed energy weapons 50) is limited to at
most 100 Kelvin. With cryogenic cooling, the maximum junction
temperature rise will exceed 300 Kelvin. The SCR's ability to
safely conduct such large overloads will allow the rectifiers to
electronically control faults, continue to operate with some
devices damaged or destroyed, while the good heat transfer
characteristics of boiling liquid nitrogen permits a rapid recovery
to normal operating temperatures.
[0022] Third, cryocooling substantially reduces the difficulty of
connecting hot power sources to a superconducting bus and
superconducting motors. Cryocooled rectifiers and motor drives
operate between the room temperature equipment and the
superconducting materials. Their large cold mass and relatively
small conductor cross-sections (enabled by the 6.times. reduction
in copper resistivity) greatly simplify the design of the
transition to superconducting temperatures, and reduce consumption
of precious liquid helium.
[0023] Disconnects 32, 52 and/or 82 may be implemented using
cryogenically cooled arcless DC switches and circuit breakers. The
power system may include DC switches rated at 6 kA and capable of
interrupting full rated current with no arc. This technology may be
extended to cryogenic rectifiers and superconducting DC bus.
Existing switches have a size of 32".times.24".times.18",
approximately {fraction (1/10)} the volume of conventional switches
utilizing arc chutes. Cryogenic cooling could further reduce the
size (although mechanical forces developed by large fault currents
may limit the amount of reduction possible) and will certainly
extend the maximum permissible fault current that the device can
safely interrupt.
[0024] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustration and not limitation.
* * * * *