Position Estimation Error Reduction Based on a Complex-Coefficient Extended State Observer for IPMSM Sensorless Drives

The sensorless control of interior permanent magnet synchronous motor (IPMSM) based on back electromotive force (BEMF) estimation has been widely studied. However, non-ideal conditions such as inverter nonlinearity and flux spatial harmonics inevitably cause harmonics in the estimated BEMF, especially the dominant fifth and seventh harmonics, which eventually lead to rotor position estimation error in the conventional BEMF observer. To reduce the rotor position estimation error, this paper proposes a first-order complex-coefficient extended state observer (CCF-ESO), which exhibits a frequency-adaptive bandpass characteristic and can effectively suppress the BEMF harmonics without additional digital filters. The proposed CCF-ESO is verified by experiments on a 1.2 kW IPMSM drive platform.