Research On Measuring The Frequency-impedance Characteristic Of Shunt Filter Groups Based On Harmonic Wavelet Analysis

Reactive power compensator/ passive shunt filter group are widely used in power grid. They are often composed of capacitor, inductor and resistor. Their main usages were reactive power compensation and harmonic filtering. Every harmonic filter group has its own frequency-impedance characteristic which is determined by the value of all the components. The frequency-impedance characteristic can reflect the performance of the filter group and can indicate whether some component has been deteriorated. But up to now the measurement for frequency-impedance characteristic can only be done in off-line mode. The measuring test will be a hard work, the interval between two tests will be long and it will not be in time to find out defection in components. In this paper a measuring method was discussed by recording the current and voltage waveform during some transient status. The current waveform and voltage waveform will be filtered by harmonic wavelet and processed by proper transformation, and finally we will get the frequency-impedance characteristic. By this method it will be evidently simplified to measure the frequency-impedance characteristic of a reactive power compensator/ passive shunt filter group. In this paper the measuring principle is tested with a simulation waveform and a site recorded waveform. The test result is overall satisfactory. Finally the reasons for calculation error are discussed and the technical measures to improve the measuring accuracy are suggested.