Improved Rotor Position Estimation in Sensorless SPMSM Using NSMO and QPLL-Based Frequency Control for Wide Speed Range

In sensorless control accurate position estimation is crucial for improving system dynamics and achieving better performance under dynamic operating conditions. The fixed-gain proportional integral (PI) controller in conventional quadrature phase-locked loops (CQPLLs) exhibits limited performance over a wide speed range due to poor adaptability and degraded tracking under dynamic conditions. Hence, this article proposed the limit frequency control (LFC) within a QPLL for effective rotor position estimation in sensorless FOC for surface permanent magnet synchronous motor (SPMSM). The proposed method uses a nonlinear sliding mode observer (NSMO) with LFC-QPLL for speed and position estimation. The proposed control adjusts the bandwidth of the loop filter and allows adaptive tunning of the PI controller within a QPLL. The effectiveness of the proposed control is validated through theoretical analysis, MATLAB/Simulink simulations, and hardware experiments, demonstrating its robustness under dynamic operating conditions. A comparison between the proposed method with different PLLs is performed. Finally, the proposed control is validated in contrast to conventional method and implemented on a four-pole, 1.07 kW PMSM using dSPACE DS1104. In hardware, the position estimation errors using LFC-QPLL at 0.1 and 1 pu are −1.5° and 4.3°, respectively, whereas under the same conditions, the fixed-gain CQPLL yields errors of −18° and −8.75°.