Rotor position error compensation based on third harmonic back-EMF in flux observer sensorless control

Two rotor position error compensators based on third harmonic back-EMF are proposed to improve the performance of rotor position estimation in flux observer sensorless control. Third harmonic flux-linkage obtained from the integration of third harmonic back-EMF is superior to conventional flux observer in terms of insensitivity of machine parameters. Different from the conventional rotor position estimation based on zero crossings of third harmonic flux-linkage, the continuous signal is taken as reference of compensators, and the estimated rotor position/speed error in flux observer can be compensated to improve the accuracy of the estimated rotor position. Furthermore, the robustness can also be enhanced due to the mutually complementary between the compensators and flux observer. Several experiments have been carried on a permanent magnet synchronous machine, and the experimental results validate that the position-error-based compensator has more accurate rotor position estimation under steady-state, whilst the speed-error-based compensator can achieve better response and robustness under dynamic situation.