Research On Control Of Five-Phase Permanent Magnet Synchronous Motor Based On Harmonic Current Injection

Nowadays,the development of multilevel inverter technology breaks through the constraint of power electronic devices and clears the way for the control research and application of multiphase motor.More and more high-power applications,such as all-electric aircraft,electric vehicles and ship propulsion,require the motor control system to have the characteristics of high reliability,good fault tolerance and high-power density,because of the advantages of both multi-phase and permanent magnet synchronous motors,five-phase permanent magnet synchronous motor(PMSM)has good application prospects in these fields.This dissertation chooses five-phase PMSM with third harmonic in air-gap flux density as the research object,and its magnetic potential analysis,mathematical modeling,third harmonic current injection theory and SVPWM algorithm(Space Vector Pulse Width Modulation Strategy)are deeply studied and tested.Firstly,in order to analyze the winding magnetic potential of five-phase PMSM,the winding function is introduced,and the magnetic potential is decomposed by Fourier transform.In this way,the dissertation determines the different effects between the harmonics of different times of phase current and the harmonics of winding,and verifies the hypothesis that the third harmonic current can react with the third harmonic in the winding function of motor to produce constant torque to increase the torque density.At the same time,based on the conclusion of magnetic potential analysis,the decoupling mathematical model of five-phase PMSM with third harmonic winding is deduced.Five-phase PMSM can achieve similar control performance as DC motor by decoupling control components,by the using of rotating coordinate transformation.Secondly,in order to minimize the copper consumption of the motor,a vector control scheme based on“I_d=0”is formulated.Considering that the traditional single-space control of three-phase motor can't satisfy the purpose of injecting third harmonic current,the control vector dimension of the control strategy is increased,and the double-space closed-loop control strategy is adopted to restrict the third harmonic current injection from two aspects:the amplitude ratio of harmonic current to fundamental current and the phase relationship.While ensuring the maximum output torque of the motor,the output phase current can be symmetrical.A model of speed-current double closed-loop speed regulation system is built in Matlab,which can improve the dynamic response characteristics of the system.Thirdly,after discussing the implementation process of SVPWM algorithm,the performance of four different SVPWM algorithms in third harmonic injection is compared.The two-vector SVPWM algorithm is developed from three-phase motor vector control strategy,which can only achieve single-space current closed-loop,so it can not control the harmonic component of the third harmonic subspace.After introducing two new basic voltage vectors,the standard four-vector SVPWM guarantees the unique solution of the target voltage vector synthesizer switching time in two subspaces,and ensures the closed-loop control of the third harmonic component,so it can realize the controllable injection of the third harmonic current.The simplified four-vector SVPWM algorithm is not much different from the two-vector SVPWM in principle,although it can introduce the third harmonic component by changing the amplitude length of the new synthetic vector,however,the third harmonic component is in an open-loop state.The six-vector SVPWM algorithm breaks the thinking formula and chooses different basic voltage vectors in two planes to synthesize the fundamental and third harmonic voltage components.It not only achieves high utilization ratio of DC bus voltage,but also achieves closed-loop control of third harmonic current.Finally,a hardware-in-the-loop simulation experiment platform is built based on dSPACE 1007.Through the experiment of harmonic injection,the dynamic stability of the control system and the effectiveness of the modulation strategy in the third harmonic current injection are verified.The third harmonic current is injected into the five-phase motor with different contents,by comparing the experimental results with the simulation data,it is proved that the standard four-vector SVPWM and the six-vector SVPWM can realize the controlled injection of the third harmonic current.When the injection rate of the third harmonic current is 20%,the output torque of the motor reaches the maximum.