Research On The Control Strategy Of Five-phase Pmsm Based On Third Harmonic Injection

To alleviate the increasingly serious environmental problem and adhere to sustainable development strategy,the electric vehicles for its green features arise at the historic moment. The reliability and security of these systems are highly demanded in recent years. Hoping a system can have enough fault-tolerant capability, and it may still work reliable when the motor drive system encounter some failures. Compared to the conventional three-phase motor, multi-phase motor can greatly improve its fault tolerance ability. On the other hand, it may also have the good performance of high speed range and overload rating which provides large potential for the control system’s safety.Firstly, during the normal operation of PMSM, the model of the synchronous rotating reference frame is deduced. While air gap magnetic field is sinusoidal, singleplane vector control strategy is proposed, and when there is third harmonic in the air gap magnetic field, daul-plane vector control strategy is analyzed, then the control system simulation model is built to validate the control strategy. Study on the third harmonic current injection method later to increase the output torque of the motor under the current RMS constraints, current amplitude constraints, torque and loss ratio constraints. Finally, the third harmonic current injection rates is optimized and verified with finite element emulation software Ansoft.Secondly, depending from the three-phase motor SVPWM method, both NFVSVPWM modulation and CPWM algorithm with zero-sequence injection used for the five-phase inverter are analyzed and compared. And ZI-CPWM method can be extended so that it can be applied to third harmonic current injection dual space vector control strategy. Then five-phase vector control system simulation model is established using MATLAB’s Simulink tools to verify the two PWM methods.Thirdly, research on the control strategy of five-phase fault-tolerant PMSM is undertaken, which is applied in open-circuit fault. The traditional fault-tolerant strategy relies on current hysteresis control, the switching frequency is not fixed, so that the decoupling vector control strategy is proposed. Under conditions of the the minimum copper loss and the current amplitude equal restrictions, zero-sequence component is optimized.In the case of non-sinusoidal gap magnetic field consideration, mathematical model of the third harmonic space is derived in this chapter, and we can use the third harmonic injection method to eliminate twice and fourth torque ripple, and the performance is validated through the finite element simulation.Finally, hardware design of the control system is completed, including the power drive unit and control unit using TMS320F28335 DSP chip as the core. At the same time software design and programming are finished. The experimental platform is constructed to verify the correctness and feasibility of the proposed control algorithm, including PWM method, vector control strategy and fault tolerant control strategy in the paper.