Study On Fault Tolerant Drive Of Permanent Magnet Synchronous Motor Based On Four-Switch Three-Phase Inverter

Study on fault-tolerant technique is one of the important research directions in modern AC servo system to improve the reliability and stability of the system. However, power electronic devices are prone to failure of the weak links. To solve the above problems,fault-tolerant topology is improved to achieve running stably when power devices are in failure. The four-switch three-phase running mode is introduced to acquire fault-tolerant running on the basis of the characteristics of lower cost, unrestricted with winding connection, integrating with space vector pulse width modulation(SVPWM). The vector control is adopted with the current as variable, having a better current tracking performance, be tracked and regulated rapidly the uneven current resulting of the unbalance of the bus capacitor voltage, reducing the current ripple and torque ripple. In this paper, the four-switch three-phase fault-tolerant driver system is researched for permanent magnet synchronous motor(PMSM).Firstly, the theory of vector control and PID control algorithm are analyzed and the PID parameters are setted on the basis of the different mathematical models of PMSM. Then the SVPWM principle and DSP Implementation are further studied and SPWM and SVPWM techniques are compared.Secondly, the principle of the three-phase four-switch inverter and the algorithm four-switch SVPWM are described. Then several methods for implementation four-switch SVPWM using DSP are proposed. Considering the effect of capacitive impedance on the drive performance, that led to the DC bus capacitor voltage unbalance are pointed out, next the SVPWM voltage imbalance formula are detailedly discussed. The three-phase four-switch vector control system can effectively track the three-phase sinusoidal current, automatically compensate the unbalanced voltage, reduce current ripple and torque ripple.Finally, the proposed vector control system is simulated under the Matlab / Simulink, the hardware and software of the PMSM drive system are designed based on the TMS320LF2812. Then three-phase four-switch fault-tolerance control is realized. The simulation results as well as experimental ones illustrate the validity and efficiency of the proposed algorithm.