Method of damping electromechanical oscillations on a power system

Patent metadata

Field	Value
Publication number	US-2018138709-A1
Application number	US-201715809669-A
Country	US
Kind code	A1
Filing date	Nov 10, 2017
Priority date	Nov 14, 2016
Publication date	May 17, 2018
Grant date	—

Abstract

A method is for damping electromechanical oscillations on a power system by injecting reactive power generated by one or more wind energy turbines, wherein a reactive power controller is adapted to determine a reference reactive power value depending on an actual system voltage. The method includes: measuring oscillation data associated with the power system, filtering the measured oscillation data to remove a steady state offset, determining a frequency value and an amplitude value from the filtered data, and triggering a damping according to at least one of the following: the frequency value determined from the filtered data falling within a predetermined frequency interval, and the amplitude value determined from the filtered data exceeding a predetermined threshold value. The damping of the electromechanical oscillations on the power system is achieved by compensating a gain and a delay applied by the reactive power controller to the reference reactive power value.

First claim

What is claimed is:

1 . A method of damping electromechanical oscillations on a power system by injecting reactive power generated by one or more wind energy turbines, wherein a reactive power controller is adapted to determine a reference reactive power value (Q ref ) depending on an actual system voltage (U meas ), the method comprising:
measuring oscillation data associated with the power system; filtering the measured oscillation data to remove a steady state offset; determining a frequency value and an amplitude value from the filtered oscillation data; and, triggering a damping according to at least one criteria of the following:
the frequency value determined from the filtered oscillation data falling within a predetermined frequency interval, and
the amplitude value determined from the filtered oscillation data exceeding a predetermined threshold value; and,
wherein the damping of the electromechanical oscillations on the power system is achieved by compensating a gain and a delay applied by the reactive power controller to the reference reactive power value (Q ref ).

2 . The method of claim 1 , wherein the measured oscillation data correspond to the actual system voltage (U meas ).

3 . The method of claim 1 , wherein the measured oscillation data correspond to the reference reactive power (Q ref ) as determined depending on the actual system voltage (U meas ).

4 . The method of claim 1 , wherein the step of filtering of the measured oscillation data includes band-pass filtering so as to eliminate an influence of frequencies higher and lower than frequencies of the electromechanical oscillations on the damping.

5 . The method of claim 1 , wherein the predetermined frequency interval is between 0.2 Hz and 1.5 Hz.

6 . The method of claim 1 , wherein the predetermined frequency interval is between 0.5 Hz and 1.1 Hz.

7 . The method of claim 1 , wherein the predetermined frequency interval is between 0.6 Hz and 1 Hz.

8 . The method of claim 1 , wherein the oscillation data are applied to a 2 nd -order lag element (PT2).

9 . The method of claim 8 , wherein the 2 nd -order lag element (PT2) depends on at least one of the following data obtained from the oscillation data: frequency, gain, phase and amplitude.

10 . The method of claim 1 , wherein an additional continuous power oscillation damping is provided, which comprises the steps:
a) applying a gain and a shift to the filtered oscillation data to compensate
i. a gain applied to the reference reactive power value (Q ref ) by the reactive power controller and
ii. a delay applied to the reference reactive power value (Q ref ) by the reactive power controller; and to generate corrected oscillation data; and,
b) determining a reactive power setpoint (Q set ) based on the reference reactive power value (Q ref ) and the difference between the oscillation data and the corrected oscillation data.

11 . A wind farm connected to a power system, the wind fam comprising:
a plurality of wind energy turbines; a wind farm controller configured to provide setpoints for active and reactive power to each of the plurality of wind energy turbines; a measurement device for measuring oscillation data associated with the power system; the wind farm controller including a filter unit for removing a steady state offset from the measured oscillation data; the wind farm controller further including a reactive power controller configured to provide a reference reactive power value (Q ref ) depending on an actual system voltage (U meas ); the wind farm controller further including a power oscillation damping device (POD-device) adapted for damping electromechanical oscillations on the power system and to compensate at least one of the following effects caused by the reactive power controller:
a gain applied to the reference reactive power value (Q ref ) by the reactive power controller and
a delay applied to the reference reactive power value (Q ref ) by the reactive power controller;
wherein the wind farm controller is configured to output a reactive power setpoint (Q set, WTGs ) to at least one of the plurality of wind energy turbines based on the reference reactive power value (Q ref ) and the compensated output of the POD-device.

12 . The wind farm of claim 11 , wherein the wind farm controller comprises a switch unit configured to determine a frequency value and a amplitude value from the filtered oscillation data and to switch the POD-device based on at least one of the following criteria:
the frequency value determined from the filtered oscillation data falling within a predetermined frequency interval, and the amplitude value determined from the filtered oscillation data exceeding a predetermined threshold value.

13 . The wind farm of claim 11 , being adapted for damping electromechanical oscillations on the power system according to claim 1 .

Assignees

• Nordex Energy Gmbh

Inventors

• Hamann Niels

Classifications

• H02J3/00142

  Oscillations concerning frequency · CPC title

• H02J3/0014 Primary

  for preventing or reducing power oscillations in networks · CPC title

• H02J3/18

  Arrangements for adjusting, eliminating or compensating reactive power in networks · CPC title

• F03D7/048

  controlling wind farms · CPC title

• F05B2220/706

  an electrical generator · CPC title