Real-time small-signal stability assessment of power electronic-based components in contemporary power systems

Patent metadata

Field	Value
Publication number	US-9316701-B1
Application number	US-201514702063-A
Country	US
Kind code	B1
Filing date	May 1, 2015
Priority date	May 6, 2014
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

A novel method for real-time small-signal stability analysis for power electronic-based components in a power system. The method is based on impedance measurement techniques and Generalized Nyquist Criterion. The method is capable of real-time application. The method may be used to monitor a system in real-time by perturbing the system persistently and utilizing the system's responses to calculate source/load impedance in time-domain and based on d-q impedance measurement theory. Time-domain results may be transferred to frequency-domain results by taking advantage of a fast Fourier transform algorithm (or optionally discrete Fourier transformer for discrete systems) and monitoring the system's stability by obtaining a Nyquist contour and employing Generalized Nyquist Criterion or unit circle criterion.

First claim

What is claimed is:

1. A method comprising:
providing non-transitory computer readable media as executed by a system controller comprising a specialized chip to perform a method for real-time analysis of small-signal stability of a power system comprising at least one power electronic-based component, the method comprising:
observing the power system in a real-time operational mode, the power system comprising a source side and a load side from a perspective of the power electronic-based component;
perturbing the source side of the power electronic-based component by injecting a current of about 0.5 to about 1 percent of a nominal current of the power system at the source side, and perturbing the load side of the power electronic-based component by varying a voltage of the power system;
measuring currents and voltages at the source side and at the load side;
determining a phase of the power system using single-phase Phase Lock Loop;
transforming the measured source side current and voltage and the measured load side current and voltage to a d-q reference frame using the determined phase of the power system;
transferring time-domain source side current and voltage values and time-domain load side current and voltage values to frequency-domain current and voltage values using Fourier transforms;
calculating a frequency-domain return-ratio matrix in the d-q reference frame using the frequency-domain source side current and voltage values and the frequency-domain load side current and voltage values;
plotting a Nyquist contour of a d-d component using the frequency-domain return-ratio matrix; and
evaluating small-signal stability of the power system using stability criteria.

2. The method of claim 1 , wherein perturbing the power system comprises perturbing the source side and the load side of the power electronic-based component simultaneously.

3. The method of claim 2 , wherein a frequency of the perturbations range from about 0.1 Hz to about 1000 Hz.

4. The method of claim 2 , wherein perturbing the source side of the power electronic-based component comprises varying a current of the power system.

5. The method of claim 1 , wherein perturbing the load side of the power electronic-based component comprises injecting a voltage of about 0.5 to about 1 percent of a nominal voltage of the power system.

6. The method of claim 1 , wherein perturbing the power system comprises more than one independent perturbation.

7. The method of claim 6 , wherein the one or more independent perturbations occur over a range of frequencies other than a fundamental frequency of the power system.

8. The method of claim 7 , wherein the one or more independent perturbations are based on responses of the power system to one or more previous perturbations.

9. The method of claim 1 , wherein using Fourier transforms further comprises defining a phase and magnitude of the current of the load side and the source side of the power system.

10. The method of claim 1 , wherein the stability criteria comprises unit circle criterion or Generalized Nyquist criterion.

11. The method of claim 1 , wherein evaluating the small-signal stability of the power system further comprises defining a relative stability of the power system and comparing the relative stability to instability borders of the power system.

12. The method of claim 1 , wherein evaluating the small-signal stability of the power system further comprises utilizing Nyquist immittance criterion.

13. A method comprising:
providing non-transitory computer readable media as executed system controller comprising a specialized chip to perform a method for real-time analysis of small-signal stability of a power system comprising at least one power electronic-based component, the method comprising:
observing the power system in a real-time operational mode, the power system comprising a source side and a load side from a perspective of the power electronic-based component;
perturbing the source side of the power electronic-based component by injecting a current of about 0.5 to about 1 percent of a nominal current of the power system using shunt current injection;
perturbing the load side of the power electronic-based component by varying a voltage of the power system using series voltage injection;
measuring voltages and currents due to perturbations at the source side and at the load side;
determining a phase of the power system using single-phase Phase Lock Loop;
transforming the measured source side current and voltage and the measured load side current and voltage to a d-q reference frame using the determined phase of the power system by Phase Lock Loop;
transferring time-domain source side current and voltage values and time-domain load side current and voltage values to frequency-domain current and voltage values using Fourier transforms;
calculating a frequency-domain return-ratio matrix in the d-q reference frame using the frequency-domain source side current and voltage values and the frequency-domain load side current and voltage values;
plotting a Nyquist contour of a d-d component using the frequency-domain return-ratio matrix; and
evaluating small-signal stability of the power system using stability criteria.

14. The method of claim 13 , wherein perturbing the power system comprises more than one independent perturbation.

15. The method of claim 14 , wherein the one or more independent perturbations are based on responses of the power system to one or more previous perturbations.

16. The method of claim 14 , wherein the one or more independent perturbations are based on responses of the power system to one or more previous perturbations.

17. A method comprising:
providing non-transitory computer readable media as executed system controller comprising a specialized chip to perform a method for real-time analysis of small-signal stability of a power system comprising at least one power electronic-based component, the method comprising:
observing the power system in a real-time operational mode, the power system comprising a source side and a load side from a perspective of the power electronic-based component;
perturbing the power electronic-based component by varying a voltage of the power system using series voltage injection;
measuring a current and a voltage at the source side and at the load side;
determining a phase of the power system using single-phase Phase Lock Loop;
transforming the measured source side current and voltage and the measured load side current and voltage to a d-q reference frame using the determined phase of the power system;
transferring time-domain source-side current and voltage values and time-domain load side current and voltage values to frequency-domain current and voltage values using fast Fourier transforms;
calculating a frequency-domain return-ratio matrix in the d-q reference frame using the frequency-domain source side current and voltage values and the frequency-domain load side current and voltage values;
plotting a Nyquist contour of a d-d component using the frequency-domain return-ratio matrix; and
evaluating small-signal stability of the power system using unit circle criterion or Generalized Nyquist Criterion.

18. The method of claim 17 , wherein perturbing the power system comprises more than one independent perturbation.

Assignees

• Univ Florida State Res Found

Inventors

• Salmani Mohamadamin
• Edrington Chris S

Classifications

• G01R31/40 Primary

  Testing power supplies (testing photovoltaic devices H02S50/10) · CPC title

• G01R27/00

  Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom · CPC title

• G01R19/2513 Primary

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title

• G01R27/16

  Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line · CPC title

• G01R27/02

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title