Sensorless Control of Five-Phase Permanent-Magnet Synchronous Motor Based on Third-Harmonic Space

Different from three-phase motor, the decoupled model of five-phase motor contains two orthogonal subspaces. In this article, a sensorless hybrid control strategy of five-phase permanent-magnet synchronous motor based on third-harmonic space with no need of motor parameters for whole speed range operation is proposed. At low-speed range, a high frequency pulse voltage is injected into the third-harmonic space to obtain the rotor position information, and the torque ripple is reduced by controlling the third-harmonic space current. Meanwhile, linear extended state observers are applied to replace the low-pass and band-pass filters for signal processing. At middle- and high-speed ranges, the back electromotive force at third-harmonic space is obtained to estimate the rotor position by controlling the third-harmonic space current. Compared with conventional methods, motor parameters and additional circuits are not needed. Software phase-locked loops are also adopted to estimate the rotor position. During the switch-over area, the two position estimation methods are both enabled for the sensorless control. The experimental results demonstrate that the robustness of the hybrid sensorless control system is well-performed in the whole speed range.