DISTRIBUTED ELECTRICAL MICROGRID CONTROL

• US 20160179116A1
• Filed: 12/18/2014
• Published: 06/23/2016
• Est. Priority Date: 12/18/2014
• Status: Active Grant

• Current Assignee: Solantro Semiconductor Corp. (China Electronics Corporation)
• Original Assignee: Solantro Semiconductor Corp. (China Electronics Corporation)
• Inventors: BACQUE, James Benson, ORR, Raymond Kenneth, Keyes, Edward Patrick
• Granted Patent: US 9,812,863 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G05F 1/625 wherein it is irrelevant whether the variable actually regulated is ac or dc
• CPC Class Codes: H02J 3/18 Arrangements for adjusting, eliminating or compensating reactive power in networks for adjustment of voltage H02J3/16
• CPC Class Codes: H02J 3/241 The oscillation concerning frequency

Abstract

An electrical power source includes a power converter and either an electrical generator or an electrical energy storage device. Power flow is controlled through control of the power converter based on a voltage source and resistance model of the electrical power source. A power converter for an electrical generator is controlled to synthesize a constant voltage of the voltage source and a variable value of the resistance. The resistance value is controlled to deliver a maximum available output power to the electrical microgrid over a range of microgrid voltages up to a voltage below a maximum allowable voltage of the electrical microgrid. For an electrical energy storage device, the power converter is controlled to synthesize a resistance value of the resistance that is dependent upon a phase angle between the voltage at the microgrid side of the electrical power source and current of the electrical energy storage device.

Claims

1. A method comprising:

monitoring voltage at a microgrid side of an electrical power source in an electrical microgrid, the electrical power source comprising an electrical generator and a power converter coupled to the electrical generator at the microgrid side of the electrical generator, the electrical generator having a variable maximum available output power;

monitoring voltage at an electrical generator side of the power converter of the electrical power source;

varying power flow between the microgrid and the electrical power source by controlling the power converter to synthesize, in a voltage source and resistance model of the electrical power source, a constant voltage of the voltage source and a variable value of the resistance,

controlling the power converter comprising controlling the value of the resistance to deliver the maximum available output power to the electrical microgrid over a range of microgrid voltages up to a first voltage V_MAX1 below a maximum allowable voltage V_MAX of the electrical microgrid.

2. The method of claim 1, the constant voltage comprising the maximum allowable voltage V_MAX of the electrical microgrid.

3. The method of claim 1, controlling the power converter further comprising controlling the power converter to provide power output to the electrical microgrid by varying the resistance value of the resistance according to

4. The method of claim 1, controlling the power converter further comprising controlling the power converter to provide power output to the electrical microgrid that monotonically decreases with microgrid voltage to zero power output at the voltage V_MAX.

5. A method comprising:

monitoring voltage at a microgrid side of an electrical power source in an electrical microgrid, the electrical power source comprising an electrical energy storage device and a power converter coupled to the electrical energy storage device at the microgrid side of the electrical energy storage device;

monitoring voltage at an electrical energy storage device side of the power converter of the electrical power source;

controlling power flow between the microgrid and the electrical power source by controlling the power converter to synthesize, in a voltage source and resistance model of the electrical power source, a resistance value of the resistance that is dependent upon a phase angle between the voltage at the microgrid side of the electrical power source and current of the electrical energy storage device.

6. The method of claim 5, controlling the power converter comprising controlling the power converter to synthesize the resistance value as R_STOR:

7. The method of claim 5, controlling the power converter comprising controlling the power converter to synthesize, for a purely resistive microgrid, the resistance value as R_STOR:

8. The method of claim 5, controlling the power converter comprising controlling a voltage of the voltage source differently depending on whether the electrical energy storage device is to charge or discharge.

9. The method of claim 8, controlling the power converter comprising controlling the voltage of the voltage source so that power is supplied from the electrical energy storage device to the electrical microgrid when a voltage of the electrical microgrid V_GRID is less than a nominal voltage V_NOM, and power is supplied to the electrical energy storage device from the electrical microgrid when V_GRID>

V_NOM.

10. The method of claim 8, controlling the power converter comprising controlling the voltage of the voltage source based on a state of charge of the electrical energy storage device, with a dependence of the voltage of the voltage source monotonically increasing with the state of charge between an upper limit and a lower limit.

11. The method of claim 9, whereby V_GRID provides an output power status of the electrical energy storage device.

12. The method of claim 5, controlling the power converter comprising controlling a voltage of the voltage source to track the voltage at the microgrid side of the electrical power source after a maximum value of output power from the electrical energy storage device is reached.

13. The method of claim 5, controlling the power converter comprising controlling the voltage of the voltage source based on a state of charge of the electrical energy storage device, with a dependence of power output from the electrical energy storage device to the electrical microgrid monotonically increasing with the state of charge.

14. The method of claim 5, further comprising:

monitoring a state of charge of the electrical energy storage device,

controlling the power converter comprising controlling the power converter to synthesize the resistance value of the resistance dependent upon the phase angle while the state of charge is above a threshold state of charge, and controlling the power converter to decrease power output from the electrical energy storage device to the electrical microgrid by increasing the resistance value of the resistance when the state of charge is at or below the threshold state of charge.

15. The method of claim 5, controlling the power converter comprising controlling charging of the electrical energy storage device by controlling a voltage of the voltage source to be below a voltage of the electrical microgrid.

16. The method of claim 15, controlling the power converter comprising controlling the voltage of the voltage source to be below the voltage of the electrical microgrid according to

17. The method of claim 5, controlling the power converter comprising providing zero power flow between the electrical energy storage device and the electrical microgrid by controlling a voltage of the voltage source to track a voltage of the electrical microgrid.

18. The method of claim 15, controlling the power converter comprising controlling charging of the electrical energy storage device by controlling the voltage of the voltage source to be below the voltage of the electrical microgrid but above a minimum voltage.

19. The method of claim 5, controlling the power converter comprising controlling a power output of the electrical power source by controlling the voltage of the voltage source to be above a minimum voltage and above a voltage of the electrical microgrid.

20. The method of claim 5, controlling the power converter comprising controlling the power converter to provide asymmetric transition times for the electrical energy storage device to transition from charging to discharging and to transition from discharging to charging.

21. The method of claim 5, further comprising:

detecting a power oversupply condition in the electrical microgrid where the monitored voltage at the microgrid side of the electrical power source is above a threshold,

controlling power flow comprising controlling the electrical energy storage device to store electrical energy from the electrical microgrid responsive to detecting the power oversupply condition.

22. A method comprising:

monitoring voltages at a microgrid side of a plurality of electrical power sources in an electrical microgrid, each of the electrical power sources comprising a power source device and a power converter coupled to the power source device at the microgrid side of the electrical power source;

monitoring voltages at a power source device side of the power converter of each of the electrical power sources;

controlling power flow between the microgrid and each of the electrical power sources by controlling the power converters,

the controlling comprising, for an electrical power source that comprises an electrical generator as the power source device, controlling the power converter of the electrical power source to maintain, in a voltage source and resistance model of the electrical power source, a constant voltage of the voltage source,

the controlling comprising, for an electrical power source that comprises an electrical energy storage device as the power source device, controlling the power converter of the electrical power source to synthesize, in a voltage source and resistance model of the electrical power source, a resistance value of the resistance that is dependent upon a phase angle between the voltage at the microgrid side of the electrical power source and current of the electrical energy storage device.

23. The method of claim 22, further comprising:

controlling loads in the electrical microgrid based on one or more of;

priorities respectively associated with the loads, storability of the loads, and states of the electrical power sources.

24. The method of claim 23, further comprising:

monitoring voltage of the electrical microgrid at the loads;

determining, at the loads, the states of the electrical power sources based on the voltage.

25. The method of claim 24, further comprising:

detecting a power oversupply condition in the electrical microgrid where the monitored voltages are above a threshold.

26. The method of claim 25, further comprising:

starting the loads on the electrical microgrid responsive to detecting the power oversupply condition.

27. The method of claim 24, further comprising:

detecting a generation to storage charging and load equilibrium condition in the electrical microgrid where the monitored voltages are above a lower threshold and below an upper threshold.

28. The method of claim 24, further comprising:

detecting a storage discharge condition in the electrical microgrid where the monitored voltages decrease below a threshold.

29. The method of claim 28, further comprising:

controlling a load to deactivate the load or to prevent the load from starting on the electrical microgrid responsive to detecting the storage discharge condition.

30. The method of claim 24,

controlling loads comprising controlling the loads based on the voltage of the electrical microgrid, to disconnect each load from the electrical microgrid following a respective disconnect time delay for the load after the voltage of the electrical microgrid decreases to a respective disconnect threshold voltage for the load,

the disconnect time delay for each load being proportional to a difference between the disconnect threshold voltage of the load and a nominal operating voltage of the electrical microgrid.

31. The method of claim 24,

controlling loads comprising controlling the loads based on the voltage of the electrical microgrid, to connect each load to the electrical microgrid following a respective connect time delay for the load after the voltage of the electrical microgrid increases to a respective connect threshold voltage for the load,

the connect time delay for a first load that has a higher priority than a second load being shorter than the connect time delay for the second load.

32. The method of claim 24,

controlling loads comprising controlling the loads based on the voltage of the electrical microgrid, to connect each load to the electrical microgrid following a respective connect time delay for the load after the voltage of the electrical microgrid increases to a respective connect threshold voltage for the load,

the connect time delay for each load being proportional to a difference between the connect threshold voltage of the load and a minimum operating voltage of the electrical microgrid.

33. The method of claim 24,

controlling loads comprising controlling the loads based on the voltage of the electrical microgrid, to disconnect each load from the electrical microgrid following a respective disconnect time delay for the load after the voltage of the electrical microgrid decreases to a respective disconnect threshold voltage for the load, and to reconnect each load to the electrical microgrid following a respective reconnect time delay for the load after the voltage of the electrical microgrid increases to a respective reconnect threshold voltage for the load,

the disconnect time delays and the reconnect time delays being based on the priorities respectively associated with the loads,

the method further comprising randomizing the disconnect time delays and the reconnect time delays for loads of equal priority.