Harmonic Current Suppression And Fault-tolerant Control For Five-phase Open-end Winding Pmsm Drive System

Compared with traditional neutral connected motors,five-phase open-end winding permanent magnet synchronous motors not only have the advantages of high-power density,small torque ripples and good fault-tolerant performance,but also have the advantages of high bus voltage utilization rate and equal output of three-level inverter.Therefore,they have a good application advantage in electric vehicles,ship propulsion,all-electric aircraft and other fields.For the motor drive system,the harmonic content and reliability are key indicators related to the operation of the entire system under various conditions.However,with the increase of the number of phases and the use of dual inverter topology to drive the five-phase open-winding permanent magnet synchronous motors,the problems of efficiency and reliability will be particularly prominent,Therefore,the optimization of the matching strategy of two inverters in the drive system and accurate fault location are great significance for improving the application of five-phase open-end winding permanent magnet synchronous motor in various fields.This paper focuses on the control strategies of the drive system for five-phase open-end winding permanent magnet synchronous motor with common DC bus.A five-phase open-winding permanent magnet synchronous motor model is established in this paper and the zero-sequence current suppression strategy is studied.Because the dual inverter topology shares one DC bus,there is a zero-sequence circulating current path in the system,which will increase the system loss and produces torque ripples of the output torque.In order to better analyze the mechanism of torque ripple generated by the open-end winding motors and suppress it,an inductance model and decoupling model of the motor are established.Based on this,the voltage and torque equations including the zero-sequence space are established in the synchronous rotating coordinate system.In order to suppress the negative impact of zero-sequence current,the characteristics of the space-voltage vector of single inverter and dual inverter are analyzed,and a dual inverter space voltage vector combination that can make the output zero sequence voltage zero is found.The zero-sequence current suppression effect of the zero-voltage vector combination is utilized to maximize the system zero-equence current suppression performance.To suppress the zero-sequence current caused by zero sequence components,dead time,switch voltage drop and other reasons,the characteristics of the effective voltage vector and zero voltage vector of the dual inverter are fully analyzed,and the zero-sequence controller is designed to achieve better zero sequence current suppression effect.The mechanism and suppression method of harmonic components generated by dual inverter clamping strategy is studied.The clamping strategy is an effective method for optimizing switch sequences of open-end winding PMSM drive system.Traditional static medium and large vector clamping strategies maintain the switch state by fixing the reference voltage.However,a fixed reference voltage introduces third harmonic voltage and zero-sequence voltage into the system.To address this problem,the mechanism of the harmonic voltage generated by the static clamping strategy is first analyzed,and the position of the reference voltage vector that generates harmonic voltage is constrained,A five-phase drive system fed by dual inverter modulation strategy based on sliding clamp is proposed in this paper,which uses the optimal reference voltage equation to obtain the reference voltage of the clamp inverter,ensuring that the clamp inverter remains in a sliding state so that the clamped inverter would not introduce the harmonic voltage.At the same time,due to the optimization of the reference voltage,the modulation coefficient is further improved.The open-circuit fault diagnosis strategy for single-phase power devices in the five-phase permanent magnet synchronous motor drive system with a common DC bus fed by dual inverter topology is studied.The dual inverter topology not only has a large number of switces,but also has symmetrical switch positions.Therefore,open-circuit faults of switch in different positions would have the same fault phenomenon,which make the fault is different to be located.Traditional fault diagnosis methods are mostly based on the traditional motors with neutral connected drive system,and it is difficult to accurately locate the faulty switch in symmetrical positions.Therefore,according to the response of the zero-sequence circuit characteristics of the common DC bus,the characteristics of phase current and zero-sequence current under fault conditions is analyzed.In this method,the average value of phase current and zero-sequence reference voltage are calculated and they are used to obtain the fault combination.Then,by reconstructing the fault phase and utilizing the back electromotive force,the open-circuit fault location can be accurately obtained.The fault-tolerant control strategies for the five-phase permanent magnet synchronous motor drive system with a common DC bus fed by dual inverter topology are studied.Based on the proposed diagnostic method for open-circuit faults in switch,which can locate the faulty switch,the fault tolerance strategies under different fault types are studied.By fully utilizing the characteristics of the open-winding motor drive system with a common DC bus that allows zero sequence current to exist,this paper proposes a fault-tolerant operation method based on current injection.The anti parallel diode of the faulty switch has continuous current flow,and the diode conduction can keep the corresponding motor input connected to the corresponding bus.Therefore,the goal of outputting the target reference voltage is achieved.For multiple switch faults,this paper is conducted on the remaining four phase coordinate transformation method,and ensure fault-tolerant operation and control status under different fault conditions.