T-type Inverter Based Position Sensorless Control Of High-speed Permanent Magnet Synchronous Motor

High-speed permanent magnet synchronous motors(HSPMSM)have been widely used in the fields of Micro-turbines,CNC machine tools and compressors due to its high power density,small size,high transmission efficiency and high reliability.HSPMSM has problems such as wide speed regulation range,high stator current harmonics and difficulty in installing mechanical position sensor.Therefore,this paper focuses on the position sensorless control system of HSPMSM based on T-type inverter.Due to the small number of windings of the HSPMSM and the small stator inductance,the stator current harmonic content is high.The T-type multi-level inverter is used to reduce the stator current high-frequency harmonic by increasing the level of the output voltage.Based on the establishment of the switching function model of the T-type inverter,the three-level space vector modulation strategy is derived and simulated.The chattering increased by the asymmetry of the sliding mode surface on the two sides of the sliding mode obscuration is analyzed.The weight coefficient sliding mode observer(SMO)and the back electromotive force(EMF)feedforward SMO are proposed.In the weight coefficient SMO,the switching amount and its bandpass filtering amount are used for weighting and then used for observer control.In the back EMF feedforward SMO,the approximate back EMF is calculated by the observation angle and the speed,which is used to sliding mode control.The error sources are analyzed in detail according to the sliding mode arrival conditions,and the parameters design methods for the two proposed improved SMO are given.The normalized phase-locked loop(PLL)is used to get the rotor position and speed from the observed back-EMF.The BPF is performed before the normalized PLL,and the steady-state angle error during the acceleration and deceleration is compensated to improve the observation accuracy.The PMSM has low carrier ratio at high speed operation,which causes the control performance degradation of the current loop.The control performance degradation of the current loop adversely affects the performance of the speed loop and the observer.The continuous mathematical model of the HSPMSM is discretized,and the current loop controller is directly designed in the discrete time domain.The tuning method of the controller parameters is given to improve the performance of the current loop.Finally,a HSPMSM experimental platform based on T-type inverter is built.Based on the theoretical analysis and simulation,the experiment of HSPMSM is carried out to verify the correctness and feasibility of the proposed method.