The control scheme based on voltage model-based rotor flux observer and quadrature phase-locked loop has been extensively applied for permanent magnet synchronous motor (PMSM) sensorless drive systems. However

such scheme is susceptible to integral drift

DC bias and dynamic tracking error. Aiming at that

the sensorless control scheme based on limit cycle flux observer and iterative phase-locked loop is proposed. Firstly

the rotor flux observer is designed based on the nonlinear limit cycle oscillator. The unique closed trajectory of back electromotive forces is designed to achieve the accurate observation of rotor flux signals

thereby avoiding the integral drift or phase lag in the traditional flux observers and suppressing the influence of DC bias on flux observation. Moreover

a novel iterative phase-locked loop is further designed

which sets the initial compensation angle for iterative initial value by partitioning the estimated rotor flux signals. Based on the Newton iteration principle

an iterative operation process was designed to achieve the high-precision position observation through four iterations

improving the dynamic response of sensorless control. Finally

the effectiveness of the proposed control scheme is verified based on the PMSM drive platform.