Phase Voltage Compensation Strategy Of Pmsm For Electric Vehicle Based On Three-level Inverter

The expanding usage of motors in various sectors has set increasingly higher standards for the accuracy and efficiency of the motor drive and control system, especially at the working condition of high voltage and large capacity. The traditional motor drive and control system, based on two-level inverters, reveals such shortcoming as low output efficiency and large harmonic component, which has stemmed the improvement of the motor drive and control system in terms of the accuracy and efficiency. Consequently come multi-level inverters, to get better performance against the restriction of the structure.Multi-level inverters, compared with two-level inverters, have better performance in such aspects as lower switch stress, smaller harmonic component, better output waveform. At present, multi-level inverters have already been put into application, but the practical design of the control algorithm and the hardware does not match the theoretical usage of N-level inverters. Then as a good compromise in the family of multi-level inverters, threelevel inverters become the focus of current researches, yet are accompanied by the problem of output waveform distortion. Therefore, this thesis takes the motor drive and control system based on three-level inverters as the research subject, focuses on issues relevant to phase voltage distortion and further deduces the compensation algorithm.Firstly, the common topological structures, working principle and control algorithms of three-level inverters are introduced. Secondly, the structure of permanent magnet synchronous motors(PMSM) is stated, and the principle of action between the motor stator current and the rotor permanent magnet and the electromagnetic torque are analyzed. Then, the mathematical model of PMSM is established, and the equations of the motion of PMSM in the three-phase static coordinate system, the two-phase static coordinate system and the synchronous rotating coordinate system are derived.This thesis, by analyzing the reason for the output waveform distortion happening to three-level inverters and quantitatively analyzing the effect of relevant factors on the phase error voltage in terms of amplitude and polarity, has deduced expressions of voltage error that can be applied to various working conditions. Phase voltage compensation algorithms are proposed according to corresponding theoretical derivation.Based on the theoretical derivation of the phase voltage compensation algorithm, the simulation model is built, and the accuracy of the theoretical derivation is verified through the simulation in different working conditions. The results of the simulation experiments strongly show that the phase voltage compensation algorithm proposed in this thesis can achieve satisfactory effect in improving the output waveform and the performance of the inverters.The hardware platform of the PMSM drive and control system based on three-level inverters is established, and the stability and reliability of the system is verified through testing programs. After combining the simulation experiments and the theoretical derivation, the control programs with the compensation algorithm added into is deduced and corresponding testings are conducted in static and dynamic conditions. The analysis of experimental results demonstrates that the phase voltage compensation algorithm based on three-level inverters that is raised in this thesis has obtained good results in improving the performance of the drive and control system.