Direct current power plant
A DC power plant generating DC power from a variety of engines including a Stirling cycle engine. The DC power plant includes a relatively small start-up power source that is discontinued after the engine is running. A method for producing DC power for a load including starting up an engine using power supplied by a relatively small power supply supplemented by a capacitor bank, providing output from the engine to a generator, producing alternating current (AC) power by the generator, converting the AC power to direct current (DC) power, disabling output of the DC power during a first set of pre-selected conditions, limiting a rate of change of current of the DC power during a second set of pre-selected conditions, reducing conducted and radiated emissions of the DC power, disconnecting the DC power from the load under a third set of pre-selected conditions, and providing the DC power to the load.
1. Method of producing direct current (DC) power for an electric grid comprising:
driving a permanent magnet synchronous motor generator (PMSMG) whereby the PMSMG generator outputs alternating current (AC) power;
converting the AC power to DC power;
wherein the PMSMG and the motor drive power board control said driving;
providing the DC power to an electric grid;
receiving an angle having a waveform;
applying an increment to the angle;
generating a sine/cosine pair for the angle;
generating an inverter waveform based on the sine/cosine pair; and
computing a phase error signal based on the sine and a cosine of the grid voltage;
multiplying the sine by the voltage of the grid supply and defining a signal that contains AC and DC components wherein:
the AC component has an amplitude variation based on amplitudes of the grid supply and the inverter waveform, and having a frequency equal to twice the frequency of the grid supply when loop is locked;
the DC component has an amplitude variation based on a phase error between the grid supply and the inverter waveform;
filtering the phase error thereby eliminating a part of the AC component not relevant to control and defining filtered phase error; and
supplying the filtered phase error to the PI controller.
2. Method of claim 1 wherein said driving is performed by a Stirling engine.
3. Method of claim 1 further comprising, prior to said converting, coupling a motor drive power board and the PMSMG generator, wherein said converting is performed by the motor drive power board.
4. Method of claim 1 further comprising, prior to said providing:
coupling a DC output breaker and an arc fault detector configured to detect an arc fault condition; and
shunt tripping the DC output breaker.
5. Method of claim 1 wherein said providing depends on a condition.
6. Method of claim 5 wherein a rate of change of current of the DC power depends on a second condition.
7. Method of claim 6 wherein the second condition is an abnormal condition.
8. Method of claim 5 wherein the condition is selected from an overcurrent, a ground fault and combinations thereof.
9. Method of claim 1 further comprising reducing conducted and radiated emissions of the DC power.
10. Method of claim 1 wherein disconnecting the DC power from a load depends on a third condition.
11. The method of claim 10 wherein the third condition is an abnormal condition.
12. Method of claim 1 further comprising shunting heat of said driving into a shunt load.
13. Method of claim 12 further comprising heating water with the heat.
14. The method of claim 1 further comprising providing the DC power to: an igniter power board; a pump/fan/blower drive; an engine control I/O PCB; a system control PCB; a power control PCB; and combinations thereof.
15. Method of claim 1 wherein:
the angle has a 16-bit value;
the angle sweeps from 0-360° every 100 μsecs;
the increment has a 32-bit center frequency input and/or a 16-bit delta frequency input driven by a PI controller;
the center frequency input is a fractional value of the angle; and
the delta frequency oscillates about zero.
16. Method of claim 1 further comprising reporting to a system controller the voltage and the frequency of the electric grid.
17. Method of producing direct current (DC) power for an electric grid comprising:
driving a permanent magnet synchronous motor generator (PMSMG) whereby the PMSMG generator outputs alternating current (AC) power:
converting the AC power to DC power:
wherein the PMSMG and the motor drive power board control said driving:
providing the DC power to an electric grid;
measuring a voltage and a frequency by a first digital phase locked loop;
measuring a phase error by a second digital phase locked loop;
referencing the voltage to the second digital phase locked loop; and
defining a phase lock when:
the phase error is less than a value; and/or
the voltage is within a range.
18. Method of claim 17 wherein the first digital phase locked loop the voltage and/or the frequency are within a second range.