Method and apparatus for detecting low-frequency oscillations
AssigneeWobben Properties GmbH
InventorAramis Schwanka Trevisan
Life of this patent
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Abstract
Provided is a method for detecting low-frequency oscillations, in particular subsynchronous resonance, in an electrical supply grid, wherein the electrical supply grid has a grid voltage at a grid nominal frequency, comprising the steps of capturing at least one electrical signal from the electrical supply grid, and evaluating the electrical signal by means of wavelet analysis, during which a time-dependent frequency pattern is created by analyzing a correlation of the captured signal with a predetermined wavelet mother function, wherein the presence of a low-frequency oscillation is assumed if at least one further low-frequency frequency component is present in the time-dependent frequency pattern in addition to a fundamental component.
Claims16
A method for detecting low-frequency oscillations in an electrical supply grid having a grid voltage associated with a nominal frequency, comprising:
- capturing at least one electrical signal from the electrical supply grid, the capturing including detecting a three-phase voltage of the grid voltage;
- transforming the three-phase voltage into a d/q representation;
- evaluating the transformed three-phase voltage using wavelet analysis, including:
- generating a time-dependent frequency pattern based on analyzing a correlation between the transformed three-phase voltage and a wavelet mother function;
- detecting a presence of a low-frequency component and a fundamental component in the time-dependent frequency pattern;
- and
- in response to detecting the presence of the low-frequency component and the fundamental component in the time-dependent frequency pattern, determining that a low-frequency oscillation is present,
- wherein the method is performed at a grid connection point where a wind power installation or wind farm supplies electrical current to the electrical supply grid, and
- wherein the at least one electrical signal is a voltage at the grid connection point or a voltage proportional to the voltage at the grid connection point.
A detection device for detecting low-frequency oscillations in an electrical supply grid having a grid voltage and an associated a grid nominal frequency, comprising:
- a sensor configured to capture at least one electrical signal from the electrical supply grid, the at least one electrical signal comprising a three-phase voltage of the grid voltage;
- and
- a controller configured to:
- transform the three-phase voltage into a d/q representation;
- evaluate the transformed three-phase voltage using wavelet analysis, including:
- generating a time-dependent frequency pattern based on analyzing a correlation between the transformed three-phase voltage and a predetermined wavelet mother function;
- detecting a presence of at least one low-frequency component and a fundamental component in the time-dependent frequency pattern;
- and
- in response to detecting the presence of the low-frequency component and the fundamental component in the time-dependent frequency pattern, determining that a low-frequency oscillation is present,
- wherein the detection device is positioned at a grid connection point where a wind power installation or wind farm supplies electrical current to the electrical supply grid, and
- wherein the at least one electrical signal is a voltage at the grid connection point or a voltage proportional to the voltage at the grid connection point.
A wind power installation or wind farm configured to supply electrical power to an electrical supply grid and to be connected to the electrical supply grid at a grid connection point, the wind power installation or wind farm comprising:
- a controller configured to:
- detect low-frequency oscillations in the electrical supply grid, wherein the electrical supply grid has a grid voltage and is associated with a grid nominal frequency, and the low-frequency oscillations to be detected have a lower frequency than the grid nominal frequency;
- and
- a sensor configured to capture at least one electrical signal from the electrical supply grid, the at least one electrical signal comprising a three-phase voltage of the grid voltage;
- wherein the controller is configured to:
- transform the three-phase voltage into a d/q representation;
- evaluate the transformed three-phase voltage using wavelet analysis, including:
- generating a time-dependent frequency pattern based on analyzing a correlation between the transformed three-phase voltage and a predetermined wavelet mother function;
- detecting a presence of a low-frequency component and a fundamental component in the time-dependent frequency pattern;
- and
- in response to detecting the presence of the low-frequency component and the fundamental component in the time-dependent frequency pattern, determining that a low-frequency oscillation is present,
- wherein the sensor is positioned at the grid connection point where the wind power installation or wind farm supplies electrical current to the electrical supply grid, and
- wherein the at least one electrical signal is a voltage at the grid connection point or a voltage proportional to the voltage at the grid connection point.
Dependencies are inferred from the claim text.