Paralleled HVDC bus electrical power system architecture
A power generation and distribution system utilizes two or more AC generators each of which may be driven by a separate prime mover such as a turbine. The generators may be driven at different rotational speeds. AC power from the generators may be rectified and applied to a common DC bus. Electrical loads may be applied to the common bus and may establish an electrical power requirement. Allocation of electrical power requirement may be made among the generators based on power available from the turbines.
1. Apparatus for generating and distributing electrical power on an aircraft comprising:
a first AC generator driven by a first engine of the aircraft at a first rotational speed, the first AC generator delivering power directly to a common DC bus via a first rectifier;
a second AC generator driven by the first engine or a second engine of the aircraft at a second rotational speed different from the first speed, the second AC generator delivering power directly to the common DC bus via a second rectifier;
the common DC bus for supplying electrical power from either of the generators to an electrical load connected to the common DC bus without paralleling AC power from the first AC generator and the second AC generator; and
a supervisory controller configured to provide signaling to generator control units (GCU) to vary duty-cycles of the first and second AC generators to allocate portions of the electrical load among the first and the second AC generators while the first and second AC generators and the electrical load remain connected to the common DC bus, and
wherein generator power share is determined by the supervisory controller responsively to power available from the engines.
2. The apparatus of claim 1 wherein the common DC bus comprises sub-buses that are selectively electrically isolated from each other.
3. The apparatus of claim 2 wherein:
a first one of the sub-buses is directly interconnected with the first generator but not the second generator;
a second one of the sub-buses is directly interconnected with the second generator but not the first generator, whereby power is supplied to the electric load in the event of a short-circuit failure of either of the sub-buses.
4. The apparatus of claim 1 wherein the first and second generators are selectively electrical isolatable from the common DC bus so that continued provision of power to the electric load is achieved in the event of failure of either the first or the second generator.
5. Apparatus for generating and distributing electrical power in an aircraft with multiple turbines comprising:
a first AC generator driven by a first turbine at a first rotational speed;
a second AC generator driven at a second turbine at a second rotational speed different from the first speed;
a common DC bus interconnected with the first and second generators without paralleling AC power from the first AC generator and the second AC generator;
the common bus being selectively connected with an electrical load, which electrical load produces an electrical power requirement;
a supervisory controller configured to allocate portions of the electrical power requirement among the first and the second generators responsively to availability of turbine power, wherein
the supervisory controller continuously allocates the portions of the electrical power requirement by continuously varying the output voltage and power of the first AC generator and the second AC generator.
6. The apparatus of claim 5 wherein:
the first turbine comprises a first portion of an engine of the aircraft; and
the second turbine comprises a second portion of the engine of the aircraft.
7. A method for producing and distributing electrical power in an aircraft comprising the steps of:
driving a first AC generator at a first rotational speed;
driving a second AC generator at a second rotational speed different from the first speed;
rectifying the electric power from the first and second generators so that DC power is supplied directly to a common DC bus from the first AC generator and the second AC generator without paralleling AC power from the first AC generator and the second AC generator;
supplying power from the DC bus to electrical loads that produce an electrical power demand;
controlling electrical power output of the first and second AC generators by controlling their output voltage; and
allocating the electrical power demand among the first and second generators while maintaining the generators and the electrical loads interconnected with the common DC bus.
8. The method of claim 7 further comprising the steps of:
producing a first command signal at which the first generator produces power;
producing a second command signal at which the second generator produces power; and
wherein the step of allocating the electrical power requirement comprises varying the first and second command signals.
9. The method of claim 7 further comprising the step of:
operating the first generator as an engine starting motor for a first engine of the aircraft;
operating the second generator as an engine starting motor for a second engine of the aircraft; and
driving the starting motor for the first engine with electrical power from the second generator.
10. The method of claim 9 further comprising the step of supplying electrical power from the second generator to an electrical load other than the starting motor operation.
11. The method of claim 7 wherein the step of supplying power to a load is performed at an undiminished rate when either the first or the second generator does not produce power.