System and method for reactive power regulation

• US 8,848,400 B2
• Filed: 02/15/2012
• Issued: 09/30/2014
• Est. Priority Date: 02/15/2012
• Status: Active Grant

• Current Assignee: GE Infrastructure Technology, LLC (General Electric Company)
• Original Assignee: General Electric Company
• Inventors: Yuan, Xiaoming, Tan, Zhuohui, Klodowski, Anthony Michael
• Primary Examiner(s): Laxton, Gary L
• Assistant Examiner(s): Torres-Rivera, Alex
• Application Number:
  US13/397,055
• Publication Number:
  US 20130207622A1
• Time in Patent Office: 958 Days
• Field of Search: 363/34, 363/35, 363/36, 363/37, 323/205, 323/207
• US Class Current: 363/35
• CPC Class Codes: G05F 1/70 Regulating power factor; Regulating reactive current or power
• CPC Class Codes: H02J 3/1835 with stepless control
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

A system and method are provided for performing reactive power control. The system includes a power converter and a controller coupled to the power converter. The power converter is configured to convert a first form of electric power generated from the power source to a second form of electric power suitable to be distributed by the electrical grid. The controller is configured to monitor the electric power transmitted between the power converter and the electrical grid. The controller is further configured to decouple a positive sequence component and a negative sequence component from the monitored electric power. The controller is further configured to perform a positive reactive power control and a negative reactive power control with respect to the decoupled positive and negative sequence components. The controller is further configured to transmit a control signal to the power converter based on the positive and negative reactive power control.

Claims

1. A system for performing reactive power control, the system comprising:

a power converter coupled between a power source and an electrical grid, the power converter configured to convert a first form of electric power generated from the power source to a second form of electric power suitable to be distributed by the electrical grid; and

a controller coupled to the power converter, the controller configured to;

monitor the electric power transmitted between the power converter and the electrical grid,

decouple a positive sequence component and a negative sequence component from the monitored electric power,

perform a positive reactive power control with respect to the positive sequence component by;

generating a first d-axis positive current command according to a monitored DC voltage across a DC link of the power converter and a specified DC voltage command;

generating a first q-axis positive current command according to a calculated feedback positive reactive power and a specified positive reactive power;

regulating the first d-axis positive current command and the first q-axis positive current command to generate a d-axis positive voltage command and a q-axis positive voltage command; and

transforming the d-axis positive voltage command and the q-axis positive voltage command to generate voltage command signals,

perform a negative reactive power control with respect to the negative sequence component, and

transmit a control signal to the power converter based on the positive reactive power control and the negative reactive power control to enable the power converter to adjust a reactive power of the electric power transmitted between the power converter and the electrical grid.

2. The system of claim 1, wherein the controller is further configured to perform a positive active power control with respect to the positive sequence component and to perform a negative active power control with respect to the negative sequence component and wherein the controller is further configured to use the positive and negative active power controls in generating the control signal.

3. The system of claim 1, wherein the power source comprises an electrical machine, the power converter comprises a machine-side converter and a grid-side converter, the machine-side converter is electrically coupled to the electrical machine for converting alternating current (AC) electric power generated by the electrical machine to direct current (DC) electric power, and the grid-side converter is electrically coupled to the electrical grid for converting the DC electric power to AC electric power in response to the control signal transmitted from the controller.

4. The system of claim 3, wherein the DC link of the power converter is coupled between the machine-side converter and the grid-side converter, the system further comprises a DC sensor for measuring the monitored DC voltage across the DC link, and the controller is further configured to use the measured DC voltage in generating the control signal.

5. The system of claim 1, further comprising a voltage sensor configured to monitor a system voltage of the electric power transmitted between the power converter and the electrical grid and a current sensor configured to monitor a system current of the electric power transmitted between the power converter and the electrical grid.

6. The system of claim 5, wherein the controller comprises a crossed-coupled phase locked logic (CCPLL) circuit and a current decoupling circuit, wherein the CCPLL circuit is configured to decouple a positive sequence voltage component, a negative sequence voltage component, a positive phase angle, and a negative phase angle from the monitored system voltage;

and wherein the current decoupling circuit is configured to decouple a positive sequence current component and a negative sequence current component from the monitored system current according to the positive phase angle and the negative phase angle.

7. The system of claim 6, wherein the controller further comprises a power calculating circuit configured to calculate the feedback positive reactive power according to the positive sequence voltage component and the positive sequence current component, and to calculate a feedback negative reactive power according to the negative sequence voltage component and the negative sequence current component.

8. The system of claim 7, wherein the controller further comprises:

a pulse width modulation (PWM) modulator to supply the control signal;

a positive power regulator to generate the first d-axis positive current command according to the DC voltage across the DC link of the power converter and the specified DC voltage command and to generate the first q-axis positive current command according to the calculated feedback positive reactive power and the specified positive reactive power; and

a positive current regulator to regulate the first d-axis positive current command and the first q-axis positive current command to generate the d-axis positive voltage command and the q-axis positive voltage command and to transform the d-axis positive voltage command and the q-axis positive voltage command to generate the voltage command signals, and to supply the voltage command signals to the PWM modulator.

9. The system of claim 8, wherein the positive power regulator is further configured to generate a second q-axis positive current command upon determination that a monitored d-axis voltage is being subjected to a voltage ride through condition, and to generate a third q-axis positive current command by summing the first q-axis positive current command and the second q-axis positive current command and to generate a second d-axis positive current command upon determination that a monitored q-axis voltage is being subjected to a voltage ride through condition, and to generate a third d-axis positive current command by summing the first d-axis positive current command and the second d-axis positive current command;

wherein the positive current regulator is further configured to regulate the third d-axis positive current command and the third q-axis positive current command to generate the d-axis positive voltage command and the q-axis positive voltage command.

10. The system of claim 7, wherein the controller further comprises a pulse width modulation (PWM) modulator to supply the control signal;

a negative power regulator to generate a first d-axis negative current command according to a monitored q-axis negative voltage and to generate a first q-axis negative current command according to a monitored d-axis negative voltage; and

a negative current regulator to regulate the first d-axis negative current command and the first q-axis negative current command to generate a d-axis negative voltage command and a q-axis negative voltage command, to rotate the d-axis negative voltage command and the q-axis negative voltage command in a positive sequence, to transform the rotated d-axis negative voltage command and the rotated q-axis negative voltage command in the positive sequence to generate the voltage command signals, and to supply the voltage command signals to the PWM modulator.

11. The system of claim 10, wherein the negative power regulator is further configured to generate a second q-axis negative current command upon determination that a difference between a calculated feedback negative reactive power and a specified negative reactive power command is not zero, and to generate a third q-axis negative current command by summing the first q-axis negative current command and the second q-axis negative current command;

wherein the negative current regulator is further configured to regulate the third q-axis negative current command to generate the q-axis negative voltage command.

12. The system of claim 1, wherein performing the positive reactive power control and the negative reactive power control comprises:

calculating a positive reactive power with respect to the decoupled positive sequence component;

calculating a negative reactive power with respect to the decoupled negative sequence component; and

wherein the positive reactive power control is based on the calculated positive reactive power and the negative power control is based on the calculated negative reactive power control.

13. A method for performing reactive power control with respect to electric power transmitted between a power source and an electrical grid, the method comprising:

monitoring the electric power transmitted between the power source and the electrical grid;

decoupling a positive sequence component and a negative sequence component from the monitored electric power;

performing a positive reactive power control with respect to the positive sequence component by generating a first d-axis positive current command according to a monitored DC voltage across a DC link of a power converter and a specified DC voltage command;

generating a first q-axis positive current command according to a calculated feedback positive reactive power and a specified positive reactive power;

regulating the first d-axis positive current command and the first q-axis positive current command to generate a d-axis positive voltage command and a q-axis positive voltage command;

transforming the d-axis positive voltage command and the q-axis positive voltage command to generate voltage command signals;

performing a negative reactive power control with respect to the negative sequence component; and

adjusting a reactive power of the electric power transmitted between the power source and the electrical grid based on the positive reactive power control and the negative reactive power control.

14. The method of claim 13, further comprising:

performing a positive active power control with respect to the positive sequence component; and

performing a negative active power control with respect to the negative sequence component.

15. The method of claim 13, wherein decoupling the positive sequence component and the negative sequence component from the monitored electric power comprises:

decoupling a positive sequence voltage component, a negative sequence voltage component, a positive phase angle, and a negative phase angle from a monitored voltage of the electric power;

using the positive phase angle and the negative phase angle while decoupling a positive sequence current component and a negative sequence current component from a monitored current of the electric power; and

calculating a feedback positive reactive power and a feedback negative reactive power using the decoupled positive sequence voltage component, the decoupled negative sequence voltage component, the decoupled positive sequence current component, and the decoupled negative sequence current component.

16. The method of claim 13, further comprising

supplying the voltage command signals to a pulse-width modulation (PWM) modulator to trigger the PWM modulator to generate a control signal.

17. The method of claim 16, further comprising:

determining whether a monitored d-axis voltage is being subjected to a voltage ride through condition;

generating a second q-axis positive current command according to the monitored d-axis voltage upon determination that the monitored d-axis voltage is being subjected to a voltage ride through condition;

generating a third q-axis positive current command by summing the first q-axis positive current command and the second q-axis positive current command;

determining whether a monitored q-axis voltage is being subjected to a voltage ride through condition;

generating a second d-axis positive current command according to the monitored q-axis voltage upon determination that the monitored q-axis voltage is being subjected to a voltage ride through condition;

generating a third d-axis positive current command by summing the first d-axis positive current command and the second d-axis positive current command; and

regulating the third d-axis positive current command and the third q-axis positive current command to generate the d-axis positive voltage command and the q-axis positive voltage command.

18. The method of claim 13, wherein performing the negative reactive power control with respect to the negative sequence component comprises:

generating a first d-axis negative current command according to a monitored q-axis negative voltage;

generating a first q-axis negative current command according to a monitored d-axis negative voltage;

regulating the first d-axis negative current command and the first q-axis negative current command to generate a d-axis negative voltage command and a q-axis negative voltage command respectively;

rotating the d-axis negative voltage command and the q-axis negative voltage command in a positive sequence;

transforming the rotated d-axis negative voltage command and the rotated q-axis negative voltage command in the positive sequence to the voltage command signals; and

supplying the voltage command signals to a pulse-width modulation (PWM) modulator to trigger the PWM modulator to generate a control signal accordingly and wherein the control signal comprises a pulse signal.

19. The method of claim 18, further comprising:

determining whether a difference between a calculated feedback negative reactive power and a specified negative reactive power command is zero;

generating a second q-axis negative current command according to the calculated feedback negative reactive power and the specified negative reactive power command upon determination that the difference is not zero; and

generating a third q-axis negative current command by summing the first q-axis negative current command and the second q-axis negative current command; and

regulating the third q-axis negative current command to generate the q-axis negative voltage command.

20. A system capable of performing reactive power control, the system comprising:

a power converter, the power converter comprising a machine-side converter and a grid-side converter, the machine-side converter being electrically coupled to a power source for converting alternating current (AC) electric power to direct current (DC) electric power, the grid-side converter being electrically coupled to an electrical grid for converting the DC electric power to AC electric power; and

a controller operatively coupled to the grid-side converter, the controller configured to monitor the AC electric power transmitted between the grid-side converter and the electrical grid and to decouple a first sequence component and a second sequence component from a monitored AC electric power, the controller further configured to perform a first reactive power control with respect to the first sequence component to generate a first command signal, the controller further configured to perform a second reactive power control with respect to the second sequence component to generate a second command signal, the controller further configured to transmit a control signal to the grid-side converter in response to the first command signal and the second command signal to enable the grid-side converter to adjust a reactive power of the AC electric power transmitted between the grid-side converter and the electrical grid, wherein the controller comprises;

a voltage decoupling circuit configured to decouple a positive sequence voltage component, a negative sequence voltage component, a positive phase angle and a negative phase angle from the monitored AC electric power;

a current decoupling circuit configured to decouple a positive sequence current component and a negative sequence current component from the monitored AC electric power using the positive phase angle and the negative phase angle;

a power calculating circuit configured to calculate a feedback positive reactive power according to the positive sequence voltage component and the positive sequence current component, and to calculate a feedback negative reactive power according to the negative sequence voltage component and the negative sequence current component;

a positive power regulator configured to generate a first d-axis positive current command according to a DC voltage across a DC link of the power converter and a specified DC voltage command and to generate a first q-axis positive current command according to a calculated feedback positive reactive power and a specified positive reactive power command;

a positive current regulator configured to regulate the first d-axis positive current command and the first q-axis positive current command to generate a d-axis positive voltage command and a q-axis positive voltage command, and to transform the d-axis positive voltage command and the q-axis positive voltage command to generate voltage commands; and

a pulse width modulation (PWM) modulator configured to receive the generated voltage commands and to supply the control signal.