Position Estimation Based on Sequence Current Decoupling and Reconstruction for PMSM Drives Using Low-Frequency Injection

High-frequency (HF) noise is unavoidable with HF injection methods in sensorless permanent magnet synchronous motor (PMSM) drives, limiting its application scenarios. To reduce acoustic noise, a positive-negative sequence current (PNSC) decoupling and reconstruction-based position estimation method using low-frequency (LF) injection is proposed. Based on the positive-negative frequency characteristics of the excited currents, a cross-decoupled complex coefficient filter is used to overcome the phase shift of conventional filters under LF injection. Stability analysis and parameter design demonstrate that the proposed method achieves a phase-shift-free separation between the fundamental and the LF excited currents. Furthermore, to compensate for errors originating from the stator resistance and mutual inductance, a position error suppression method based on the reconstruction of the PNSC is proposed. A unified mapping model between the injection frequency and the estimation error is established to optimize the injection method for increasing estimation accuracy. Analysis of the current power spectral density and A-weighted curve demonstrates that the proposed method can reduce acoustic noise. Finally, the effectiveness of the proposed method is verified on a 2.2-kW interior PMSM drive platform.