DC coupled power electronics system for a fuel cell power system
In accordance with some embodiments, the present disclosure is directed to systems having a fuel cell and a turbine generator, each capable of providing electrical power to a utility grid, and methods for operating the same. The system may have a main AC bus which is coupleable to the utility grid. The fuel cell may be coupled to main AC bus through an inverter. The turbine generator may be coupled to the main AC bus through a series of inverters, one of which may include the inverter by which the fuel cell is connected to the main AC bus. One or more load banks may be provided to provide a load for electrical power generated from the fuel cell, turbine generator, or both in case the system is disconnected from the utility grid. Further support and backup systems may be provided.
1. An electric system comprising:
a main AC bus, said bus being electrically coupleable to an electric power distribution system by a transformer and switch gear;
a fuel cell having a DC output bus, said fuel cell DC output bus being electrically coupled to said main AC bus by a fuel cell inverter;
a load bank electrically coupled to said main AC bus;
a turbine generator having an AC output bus, said turbine generator AC output bus being electrically coupled to said fuel cell DC output bus by a machine inverter;
a backup generator having an AC output bus electrically coupled to said main AC bus;
an uninterruptible power supply (UPS) electrically coupled to said main AC bus; and
a control system electrically coupled to said UPS,
wherein:
said main AC bus is not electrically coupled to said electric power distribution system;
said fuel cell is generating and providing DC power to said fuel cell DC output bus;
said load bank is drawing power from said main AC bus;
said turbine generator is drawing power from said fuel cell DC output bus;
said backup generator is not providing AC power to said backup generator AC output bus; and
said UPS is drawing power from said main AC bus.
2. The electric system of claim 1 , wherein said load bank draws an amount of power equal to the difference between the power generated by said fuel cell and the power drawn by said UPS and said turbine generator.
3. A method of operating a power plant having a fuel cell and a turbine generator each capable of providing electric power to an electric power distribution system, said method comprising:
when the power plant is disconnected from the electric power distribution system:
operating the fuel cell in a power generating mode to provide power to a main AC bus and to the turbine generator;
operating the turbine generator in a motoring mode, said turbine generator drawing power from a fuel cell DC output bus;
operating the control system of said power plant, said control system drawing power from the main AC bus of the power plant through an uninterruptible power supply (UPS) electrically connected to said control system and to said main AC bus; and
providing a load bank to draw power from the main AC bus;
without operating a backup generator to provide power to the main AC bus.
4. The method of claim 3 , further comprising:
drawing, with said load bank, an amount of power equal to difference between the power generated by said fuel cell and the power drawn by said control system, and any power provided to the turbine generator.
5. The method of claim 3 , further comprising:
providing power from the fuel cell DC output bus to said main AC Bus through a fuel cell inverter.