Electricity: battery or capacitor charging or discharging – Wind – solar – thermal – or fuel-cell source
Reexamination Certificate
1999-12-20
2001-12-04
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Wind, solar, thermal, or fuel-cell source
Reexamination Certificate
active
06326763
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally related to control techniques used in power systems and, more particularly, is related to a power system and control techniques that may be used in combination with reformer-based fuel cells so as to utilize the advantages of such fuel cells while overcoming undesirable transient response characteristics the reformer-based fuel cell may have.
It is known that standard fuel cell stacks that operate directly from a predetermined chemical fuel, e.g., hydrogen fuel, in combination with a predetermined oxidant, e.g., oxygen, provide power response that is sufficient for propelling vehicles, including passenger cars, trucks, and transit buses. It is believed several prototype fuel cell transit buses using hydrogen or other fuels may be in pilot operation in the United States. Various factors, such as safety, governmental regulations, infrastructure and packaging constraints, etc., are forcing other alternatives to direct hydrogen-powered fuel cells for transportation applications. Reformer technology is currently being developed and used to produce hydrogen fuel from alternate fuels, including methanol, gasoline, etc.
When hydrogen produced by a reformer is used to power the fuel cell stacks, unfortunately, the transient power response of the overall system that powers one or more traction motors in the vehicle is typically several seconds or possibly ten seconds or more. Thus, presently available reformer-based fuel cell systems will typically have a severe transient response performance degradation, making such systems unacceptable for transportation applications, power distribution devices, hoisting applications, etc. Further, as in a standard gasoline or diesel engine internal combustion engine (ICE), the standard fuel cell stack and reformer system provides a unidirectional source of power during the process of consuming fuel, and cannot operate in the reverse direction, i.e. accept power and regenerate the chemical fuel during periods of vehicle deceleration. Thus, any energy regenerated by the traction motors during such periods of deceleration would generally be dissipated and wasted.
Thus it is desirable to provide techniques that would allow for a highly efficient power control system that using a suitable energy storage device would solve the undesirable slow transient power response of standard fuel cells operating with a reformer. It would be further desirable to provide techniques that would allow for recovering or capturing in the energy storage device energy that may be generated during periods of deceleration, e.g., when the traction motors in the vehicle act as generators of electricity, as opposed to generators of mechanical power.
BRIEF SUMMARY OF THE INVENTION
Generally speaking, the present invention fulfills the foregoing needs by providing a control system for controlling power flow in a power bus generally powered by a reformer-based fuel cell system (FCS). The control system comprises an energy storage device (ESD); a power interface unit coupled to selectively pass power bi-directionally between the energy storage device and the power bus in response to an ESD power command signal supplied to the power interface unit; and a controller coupled to the power bus to receive one or more signals indicative of the instantaneous power delivered by the fuel cell system. The controller may be configured to generate the ESD power command signal so that the energy storage device may supply power to the power bus at least during transient conditions when the instantaneous power delivered by the fuel cell system drops below a FCS power command signal.
The present invention further fulfills the foregoing needs by providing an auxiliary power system in combination with a reformer-based fuel cell system (FCS) for energizing a power bus coupled to one or more traction motor drives generally used for propelling a vehicle or hoisting objects, etc. . The power system comprises an energy storage device (ESD); a power interface unit coupled to selectively pass power between the energy storage device and the power bus in response to an ESD power command signal supplied to the power interface unit; and a controller coupled to the power bus to receive one or more signals indicative of the instantaneous power delivered by the fuel cell system and configured to generate the ESD power command signal so that the energy storage device may supply power to the power bus at least during transient conditions when the instantaneous power delivered by the fuel cell system drops below a FCS power command signal.
The present invention additionally fulfills the foregoing needs by providing a method for controlling power flow in a power bus generally powered by a reformer-based fuel cell system (FCS). The method allows for providing an energy storage device (ESD). The method further allows for selectively passing power bi-directionally between the energy storage device and the power bus in response to an ESD power command signal. The method also allows for determining the instantaneous power delivered by the fuel cell system so that the energy storage device may supply power to the power bus at least during transient conditions when the instantaneous power delivered by the fuel cell system is below a FCS power command signal.
REFERENCES:
patent: 5903449 (1999-05-01), Garrigan et al.
patent: 5905360 (1999-05-01), Ukita
patent: 6011379 (2000-01-01), Singh et al.
King Robert Dean
Sinha Gautam
General Electric Company
Tso Edward H.
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