Flux Observer Based on Enhanced Second-Order Generalized Integrator With Limit Cycle Oscillator for Sensorless PMSM Drives

In a position sensorless permanent magnet synchronous motor (PMSM) drive system, parameter mismatch will introduce estimation error in the stator flux and rotor position information. A novel flux observer based on an enhanced second-order generalized integrator (SOGI) with a limit cycle oscillator is proposed to improve the robustness of sensorless PMSM drives. Based on the SOGI structure, the proposed method constructs a nonlinear oscillator with a self-excited oscillation function that can maintain the flux trajectory oscillation even in the absence of the input stator electromotive force. The enhanced observer can converge the stator flux trajectory to its expected state under external disturbances and reduce position estimation error. Moreover, the proposed limit cycle oscillator can improve the harmonic suppression ability of the SOGI-based flux observer. The convergence and robustness of the enhanced observer are both investigated, demonstrating that the proposed method can improve the performance of the flux observer. The effectiveness of this method is verified by experiments on a 2.2-kW PMSM drive platform.