Zero Speed Sensorless Scheme for PMSM Drives Using Virtual Flux Signal Injection Based Hybrid Active Flux Observer

Sensorless zero-speed control of permanent magnet synchronous motors using high-frequency signal injection introduces acoustic noise and vibration, while conventional model-based observers fail due to unobservability and instability. This article proposes a hybrid active flux observer (HFO) based on virtual flux signal injection method. Compared to conventional sensorless control methods, this method achieves stable zero-speed sensorless control under rated load without high-frequency signal injection, eliminating additional noise and vibration. First, speed observability conditions under virtual flux signal injection are derived using local weak observability theory. Then, the boundary conditions for system stability were derived using the small signal perturbation theory. By injecting virtual flux signal into the current-model flux of the HFO, both local weak observability and stability requirements at zero speed are simultaneously satisfied. Experimental validation on a 5.2 kW interior permanent magnet synchronous motor (IPMSM) drive platform confirms the method’s effectiveness.