Research For Control System Of Five-leg Voltage Source Inverter Two Permanent Magnet Synchronous Motors

Five-leg voltage source inverters can not only reduce the costs of the controlsystem, but can also improve the fault tolerance of the dual voltage source inverterswhen failure occurs in one phase leg of the dual voltage source inverters that switch tothe operating mode of five-leg bridge inverters.This paper mainly studies themodulation technology of five-leg voltage source inverters.To resolve the issues such as long action time of zero voltage vector in thetraditional half-cycle modulation strategy, the low DC voltage use of two motors,narrow speed range and so on, this paper proposes a new duty cycle modulationoptimization strategy. Within each modulation period, pace vector pulse widthmodulation is adopted for two motors to obtain reference values corresponding to theduty cycle of the two motors drive signal, respectively. Since the zero vector does notaffect the control performance of the two motors, in the range of duty, the duty cycleof driving signal of the each phase of the two motors can be increased or decreased bythe action time a zero voltage vector without changing the control performance of themotors. Based on this characteristic, this paper adjusts the reference value of the dutycycle in the range of the duty cycle reference value by comparing the duty cyclereference value of public arm of two motors, and to meet the requirement of theswitching state of the public arms, reduce the action time of the zero voltage vectortime, improve the utilization of the DC bus voltage of the two motors, extend thespeed range and achieve the independence of the speed control.For the poor adaptive ability of PI controller parameters, and the uncertainty ofthe deviation of the reference value and the given value, which will cause thedegradation and other issues of the control performance of the system. This paper usesthe deadbeat current controller instead of the PI controller and applies it to two motorcontrol systems. Combining the mathematical model of the two motors under d-q axis,deadbeat current controller can make the output of the controller in the next timeequal to the given value of the controlled value, so as to achieve the static errorcontrol of both two motors’ currents. This control method can ensure its stability, andsimultaneously greatly improve the dynamic response of the speed of the two motors.This paper conducts the simulation and experimental analysis of the modulation and control algorithm for the five-leg voltage source inverter. The results show thatthe improved modulation strategy can effectively improve the utilization of the DCbus voltage of the two motors, extend the speed range of the two motors and thedeadbeat current controller of the five-leg voltage source inverter of two motors canachieve good dynamic performance and rapid response speed of the two motors.