Research On PMSM Drive Control System With Fault Tolerance

Permanent magnet motor with small volume, high efficiency, high speed, has been widely used in military, industry, life and other fields. The stability of the motor driving system is critical for the whole equipment. There are two commonly used control methods for permanent magnet synchronous motor: Field Oriented Control and Direct Torque Control. There is something in common. They do electromechanical energy conversion with space vector. The traditional DTC changed controlled variable with hysteresis controller while FOC uses space vector pulse width modulation.This paper introduces the method of traditional DTC and constructs the corresponding control system in MATLAB, then introduces the expected voltage DTC using space vector pulse width modulation(SVPWM) instead of hysteresis controller. Finally the paper compares the similarities and differences between the two systems and proves that SVPWM is suitable for both FOC and DTC. The paper selects the FOC of PMSM to explain fault-tolerance strategy.Traditional power converter consisting of three half-bridge does not have the ability of fault-tolerance. When a bridge arm breaks down, power converter can’t normally generate six effective space vectors. Neutral-point voltage is used instead of broken bidge arm. Simulation model is set up to study similarities and differences between six-switch three-phase SVPWM and four-switch three-phase SVPWM. The capacity of the two capacitances on the dc bus may be different and the basic space vector of four-switch SVPWM is affected by the difference. Finally a power converter model observer has been set up. The power converter model observer can recognize the power switch failure by calculated current.This paper designed the experimental platform with STM32 as the control chip, including the hardware and software. Hardware design includes main circuit, drive circuit, current/voltage detection circuit, fault switching circuit, power circuit, etc. Software part includes the main routine, zero pulse capture interrupt routine, overflow timer interrupt routine, and power interrupt subroutine to adjust current and speed and so on. The paper verifies the feasibility of control scheme and analyses the insufficient in the system. Next plan has also been done.