Method for small-signal stability assessment of power systems using source side and load side perturbations and generalized Nyquist criterion

Patent metadata

Field	Value
Publication number	US-9612293-B1
Application number	US-201615131707-A
Country	US
Kind code	B1
Filing date	Apr 18, 2016
Priority date	May 6, 2014
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A novel method for real-time small-signal stability analysis for power electronic-based components in a power system. The method may be used to monitor a power system in real-time by perturbing the source side of an electronic-based component of the power system of about 0.5 to 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 the voltage at the load side. Time-domain results of the simultaneous perturbations may be transferred to frequency-domain results and the stability of the power system may be monitored by obtaining a Nyquist contour and employing Generalized Nyquist Criterion.

First claim

What is claimed is:

1. A method for real-time analysis of small-signal stability of a power system, the method comprising:
providing non-transitory computer readable media having computer-executable instructions for performing a method of running a software program on a computing device, the computing device operating under an operating system, the method including issuing instructions from the software program 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-base 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, wherein perturbing the source side of the power electronic-based component and perturbing the load side of the power electronic-based component occurs simultaneously and independently;
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 of the frequency-domain return-ratio matrix; and
evaluating small-signal stability of the power system using General Nyquist Criterion.

2. The method of claim 1 , wherein perturbing the source side of the power electronic-based component and perturbing the load side of the power electronic-based component comprises more than one independent perturbation.

3. The method of claim 2 , wherein the one or more independent perturbations occur over a range of frequencies other than a fundamental frequency of the power system.

4. The method of claim 2 , wherein the one or more independent perturbations are based on responses of the power system to one or more previous perturbations.

5. The method of claim 1 , wherein a frequency of the perturbations range from about 0.1 Hz to about 1000 Hz.

6. The method of claim 1 , wherein perturbing the source side of the power electronic-based component comprises varying a current of the power system.

7. 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.

8. 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.

9. 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.

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

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

• G01R27/16

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

• G01R19/2513 Primary

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

• G01R19/2506

  Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values (G01R19/003 takes precedence); Details concerning sampling, digitizing or waveform capturing (displaying waveforms G01R13/00; analog sampling G01R19/0053) · 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