Coupling and Digital Control Delays Affected Stability Analysis of Permanent Magnet Synchronous Motor Current Loop Control

Under the condition of high frequency operation of permanent magnet synchronous motor (PMSM) and low control carrier ratio, the current loop control is apt to lose stability due to the influence of motor impedance coupling and digital control delays. In this paper, the current open and closed loop transfer function based on complex coefficients theory is established in the dq-axes synchronous reference frame. On this basis, the root locus method is used to analyze the coupling and digital control delay effects on the stability, and the instability conditions of the current loop are presented. Simulation and experiment prove the correctness and validity of the theoretical analysis and the proposed method.