Unified Wide-Speed Sensorless Scheme Using Nonlinear Optimization for IPMSM Drives

This paper proposes a novel unified nonlinear optimization-based speed and position estimation algorithm for interior permanent magnet synchronous motor drives at wide speed range operations. A cost function based on the voltage equations in the stationary reference frame is employed for speed and position estimation. The speed and position can be estimated by minimizing the cost function. At low speed, including the standstill condition, the cost function is modified and high-frequency sinusoidal voltage signals are injected in the estimated magnetic axis. A phase locked loop is combined with the proposed position estimator for reducing the noise of estimation results. Compared with existing sensorless methods, a unified estimator is used at low- and high-speed operations and a better performance is obtained in transient and steady-state conditions. The convexity of the cost functions with respect to the speed and position estimation errors is analyzed in the paper. The feasibility of the proposed estimation algorithm is validated with an experimental test bench.