<p>To solve the problem of fluctuation errors in the estimated back electromotive force caused by inverter nonlinearity and magnetic flux space harmonics, a sensorless control method based on an improved extended state observer and phase-locked loop is proposed for permanent magnet synchronous motor. The back electromotive force containing rotor position and speed information is expanded into a new state variable. An improved extended state observer based on adaptive fundamental extraction unit is designed to estimate the state variable, and the back electromotive force can be obtained. The adaptive fundamental extraction unit is utilized to extract the fundamental wave of the back electromotive force estimation and eliminate the harmonics. The rotor position and speed information can be calculated by an improved phase-locked loop with an extended state observer, which can eliminate disturbances and reduce estimation errors. To verify the effectiveness of the method, an experimental platform is built based on permanent magnet synchronous motors and real-time digital controllers. The experimental waveforms under different operating conditions including steady state and dynamic state are presented. The experimental results verified that the proposed method can adaptively suppress the harmonic components in the estimation. Therefore, the estimation accuracy of rotor position and speed can be improved.</p>