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

The back electromotive force (BEMF) observer for interior permanent magnet synchronous machine (IPMSM) sensorless control has been widely investigated. However, the steady-state position error of the conventional observer is positively correlated with the motor running frequency. In addition, due to the non-ideal conditions, such as inverter nonlinearity and flux spatial harmonics, the conventional LESO cannot achieve high robustness to the high-order harmonics without additional filters, which leads to harmonic position estimation error. To reduce the rotor position estimation errors, a first-order complex-coefficient extended state observer (CCF-ESO) with frequency-adaptive bandpass characteristic is proposed. Compared with the conventional LESO, the proposed CCF-ESO can eliminate the steady-state position estimation error and has a smaller harmonic position estimation error due to its better high-order harmonics immunity. The effectiveness of the proposed first-order CCF-ESO is verified by comparative experiments on a 1.2 kW IPMSM drive platform.