Simultaneous economic dispatch and frequency regulation of power systems

• US 9,742,411 B1
• Filed: 10/02/2015
• Issued: 08/22/2017
• Est. Priority Date: 08/24/2015
• Status: Active Grant

• Current Assignee: University of South Florida (State University System of Florida)
• Original Assignee: University of South Florida (State University System of Florida)
• Inventors: Fan, Lingling, Miao, Zhixin
• Primary Examiner(s): Karim, Ziaul
• Application Number:
  US14/873,501
• Time in Patent Office: 690 Days
• Field of Search: 700286-297
• CPC Class Codes: G05B 11/01 electric
• CPC Class Codes: G05F 1/66 Regulating electric power
• CPC Class Codes: H03L 5/02 of power

Abstract

Various examples are provided for feedback control of power systems. The feedback control can provide simultaneous frequency regulation and economic operation of a power system. In one example, a method includes obtaining a frequency difference associated with a generator of a power system; determining an output power adjustment based at least in part upon the frequency difference and a cost function associated with the generator; and providing a power command to a secondary frequency control of the generator, the power command based upon the output power adjustment. In another example, a generator control system includes a primary frequency controller configured to control frequency droop of a generator of a power system; and a secondary frequency controller configured to adjust output power of the generator based at least in part upon a frequency difference associated with the generator and a cost function associated with the generator.

Claims

1. A method, comprising:

obtaining, by a computing device, a frequency difference associated with a generator of a power system, where the frequency difference is based upon a current operational value of the generator and a reference value;

determining, by the computing device, an output power adjustment based at least in part upon the frequency difference and a cost function (C_i) associated with the generator, where the cost function is based upon a power dispatch level (P_i) of the generator and the output power adjustment is determined using dual decomposition based at least in part upon the cost function associated with the generator, where a dual decomposition problem for a two-area system is given by;

2. The method of claim 1, wherein obtaining the frequency difference comprises receiving a current output frequency of the generator from a distribution monitoring device and determining the frequency difference based upon the current output frequency and a reference frequency.

3. The method of claim 1, wherein obtaining the frequency difference comprises receiving a current speed of the generator and determining the frequency difference based upon the current speed and a reference speed.

4. The method of claim 1, wherein the power command is a continuous control output.

5. The method of claim 1, wherein the power command is a discrete control output.

6. The method of claim 1, comprising:

determining a second output power adjustment for a second generator based at least in part upon a frequency difference associated with the second generator and a cost function associated with the second generator, where the frequency difference associated with the second generator is based upon a current operational value of the second generator and the cost function associated with the second generator is based upon a power dispatch level of the second generator; and

providing a second power command to a secondary frequency control of the second generator, the power command based upon the second output power adjustment.

7. A generator control system, comprising:

a primary frequency controller configured to control frequency drop of a generator of a power system; and

a secondary frequency controller configured to adjust output power of the generator based at least in part upon a frequency difference associated with the generator and a cost function (C_i) associated with the generator, where the frequency difference is based upon a monitored operational value of the generator and a reference value and the cost function is based upon a power dispatch level (P_i) of the generator, and where the adjustment of the output power of the generator is determined based at least in part upon the cost function associated with the generator using dual decomposition, where a dual decomposition problem for a two-area system is given by;

8. The generator system of claim 7, comprising processing circuitry configured to:

determine an output power adjustment for the adjustment of the output power of the generator; and

provide a power command to adjust operating frequency of the generator, the power command based upon the output power adjustment.

9. The generator system of claim 8, wherein the frequency difference is determined from a current output frequency of the generator and a reference frequency.

10. The generator system of claim 9, wherein the current output frequency of the generator is provided by a distribution monitoring device of the power system.

11. The generator system of claim 8, wherein the frequency difference is determined from a current speed of the generator and a reference speed.

12. The generator system of claim 11, wherein the current speed is provided by a sensor on the generator.

13. The generator system of claim 8, wherein the power command is a continuous control output.

14. The generator system of claim 8, comprising wherein the power command is a discrete control output.

15. The generator system of claim 8, comprising a second secondary frequency controller configured to adjust output power of a second generator, wherein the processing circuitry is configured to:

determine a second output power adjustment for the second generator based at least in part upon a frequency difference associated with the second generator and a cost function associated with the second generator, where the frequency difference associated with the second generator is based upon a current operational value of the second generator and the cost function associated with the second generator is based upon a power dispatch level of the second generator; and

provide a second power command to adjust operating frequency of the second generator, the power command based upon the second output power adjustment.

16. The generator system of claim 8, wherein the secondary frequency controller comprises the processing circuitry.