Instantaneous harmonic decomposition technique for three‐phase current based on multiple reference coordinates

Abstract

Current harmonic decomposition is important to power systems. Current signal is classified into stationary and non-stationary signal according to whether the parameters change with time. This study focuses on the instantaneous harmonic decomposition of three-phase permanent magnet synchronous motor currents in non-stationary process. First, based on the definition of the instantaneous frequency in non-stationary process, the concept of the spatial frequency based on the electrical angle is proposed. Under this definition, the spatial frequency no longer varies with the rotational speed. A new instantaneous harmonic decomposition method based on multiple reference coordinates is then proposed. To verify the effectiveness of the new method, it is used to analyse constructed currents and experimental currents. Finally, the new method is compared with other analysis methods and proved to be the most accurate and effective.