Dynamic Performance Optimization of Sensorless PMSM System with Low Switching Frequency Based on Improved Deadbeat Control PLL

The dynamic performance of sensorless PMSM control systems at low switching frequency is suboptimal due to issues such as position estimation error with proportional-intregral (PI)-based phase-locked loops (PLLs) and the inaccuracy of the system model. To solve this problem, this article first proposes an improved PLL based on a deadbeat controller with a damping factor (DDCPLL). It rapidly converges the estimated rotor position to the actual position during speed transients while ensuring the smoothness of the estimated speed. This approach reduces the number of undetermined coefficients from two in traditional methods to one, simplifying the structure and facilitating implementation. Additionally, to address the current cross-coupling issues in traditional current control strategies at low switching frequencies, a novel controller was directly designed based on the discrete-domain model of the PMSM. Then, by integrating the proposed DDCPLL, a discrete-domain model of the entire positionless control system was established. The parameters of the speed controller are optimized to further enhance the system’s dynamic response performance. Furthermore, the robustness of the system under speed estimation errors and motor parameter variations is analyzed. The results demonstrate that the proposed control system maintains good robustness despite the presence of speed estimation errors and parameter mismatches. The effectiveness and feasibility of the proposed PLL and control strategy are demonstrated by detailed results.