Mechanism Analysis and Improvement of Harmonic Current Extraction for Multiple Virtual Winding Systems Under Non-Stationary Conditions

Abstract

To enhance the harmonic current extraction and control capabilities of permanent magnet synchronous motors under non-stationary conditions, this paper proposes an improved harmonic current extraction method based on multiple virtual winding systems. This paper analyzes the limitations of harmonic current extraction methods based on virtual coordinate systems under non-stationary conditions, pointing out that, due to the use of delayed signals to construct virtual currents, the fundamental component cancellation condition is violated under non-stationary conditions, thereby causing disturbances in harmonic extraction, which is most pronounced under low-speed, large load transient conditions. To address this issue, a fundamental component reconstruction method is employed to suppress the influence of the fundamental component in advance, thereby enhancing the applicability of the virtual coordinate system method under non-stationary conditions without significantly increasing computational complexity. Simulation results show that the proposed method can reduce the peak-to-peak values of harmonic extraction disturbances by approximately 69.8% and 60.5% under load step and continuous load variation conditions, respectively. In closed-loop control, it further reduces the harmonic extraction and electromagnetic torque disturbances by approximately 79.08% and 80.46%, respectively, while maintaining good steady-state performance. The proposed method is applicable to various delay-based virtual coordinate system methods, features a simple structure and convenient implementation, and exhibits strong generality.