High-Precision Harmonic Current Extraction for PMSM Based on Multiple Reference Frames Considering Speed Harmonics

Based on multiple reference frames (MRF), this article investigates high-precision harmonic current extraction for permanent magnet synchronous motor, while taking the disturbance of speed harmonics into account. First, the extraction error in MRF caused by speed harmonics is deduced and analyzed, showing that the error is nonignorable and detrimental. Second, a novel preprocessing of fundamental current reconstruction and elimination in MRF is proposed, which effectively suppresses the extraction error. Third, a variable forgetting factor recursive least squares algorithm is proposed for the fundamental current amplitude identification, which guarantees fast and accurate preprocessing. Furthermore, the above method parallelly resolves the conflict between rapid extracting and low steady-state fluctuation in MRF, which significantly enhances harmonic current extraction performance. The superiority and accuracy of the proposed algorithms are proved by experiments.