Research on stable regions of double-closed loop system for PMSM with low-pass filters

The object of this paper is to find the stable regions of current and speed regulators considering the effect of first-order low-pass filter and PI parameters of the double-closed loop system for PMSM. The influence of coupling between d axis and q axis voltage on the current loop stability is analyzed to prove the necessity of decoupling by Routh Stability Criterion. After that, this paper discusses stable regions of PI parameters and the effect of different sampling period. Finally, the stable regions in terms of the proportional gain, filter time constant and sampling period are optimized by designing the relations between the parameters of two regulators according to zero-pole cancellation in control theory, which not only ensures stability of the system but also improves the rapidity of current loop and the dynamic characteristics of speed loop. The stability analysis and optimization of stable regions are validated by Simulation.