Development Of High Energy Density Five-phase Permanent Magnet Synchronous Motor Drive System

With the industry development,the requirement for the motor’s energy density is increasing.Due to the advantages of high torque density,and high power density,the five-phase permanent magnet synchronous motor（FPMSM）has gradually attracted the extensive attention of scholars.Through the FPMSMs have significant advantages compared with the three-phase PMSMs,the FPMSMs have inevitable harmonic problems.If we do not suppress the harmonic current in the FPMSMs,the harmonic current will significantly increase the harmonic loss,and affect the five-phase machine’s efficiency and energy density.Therefore,the crucial problem for studying the high power density five-phase motor drive system is that suppresses the harmonic current,and improves the efficiency of the five-phase drive system.In the five-phase motor drive system,there are obvious 3^rd,7^th,and 9^th harmonic problems due to the non-linear air gap flux linkage and the inverter dead time.In order to reduce the harmonic loss of the five-phase motors and increase the motor drive system’s efficiency,it is necessary to suppress the harmonic current.In order to solve these problems,this paper studies the high energy density five-phase motor drive system from four aspects:the mathematical model of the five-phase motor,the PWM algorithm of the five-phase motor,the flux observation of the five-phase motor,and the high-order harmonic suppression of the five-phase motor.The structure and content of this paper are as follows:In Chapter 2,a high-fidelity mathematical model of the FPMSM and the cause of the 3^rd harmonic has been analyzed,which solves the problem that the former researchers ignored the mutual inductance between the fundamental frame and the3rdharmonic frame.A high-fidelity FPMSM model not only can benefit the analysis of the harmonic characteristics but also improve the accuracy of the FPMSM simulation system and lay the foundation for the motor control algorithm development.However,in FPMSM,the inductance and flux linkage will vary nonlinearly with the load and the electrical angle of the FPMSM.In order to build a high-precision FPMSM model,this chapter further considers the effects of the motor angle and the load.The inductances and the flux linkages under different load conditions are extracted based on the finite element analysis（FEA）software.The results show that the proposed model has high accuracy and has considered the mutual inductance between the fundamental frame and the 3rd harmonic frame in FPMSM.In Chapter 3,the PWM algorithm of the five-phase motor is researched,and a novel near six-vector（i.e.three large vectors and three medium vectors）SVPWM algorithm（NSV-SVPWM）is proposed.The proposed NSV-SVPWM algorithm can modulate the arbitrary 3rd harmonic voltage.In this chapter,a PMSM FOC control system is further built based on the NSV-SVPWM algorithm.The experimental results show that the proposed NSV-SVPWM algorithm can well suppress the third harmonic component in the motor phase current.In Chapter 4,to improve the dynamic-response ability of the FPMSM drive system,the FPMSM FOC control system mentioned in Chapter 3 has been improved by establishing a parameter-based control system.Although Chapter 2 gives an accurate mathematical model of the FPMSM,this model exist too many parameters to identify.In order to simplify the FPMSM model,a flux linkage-based voltage equation of the FPMSM is proposed in Chapter 4.Besides it,A frequency adaptive dual space flux observer is designed for the FPMSM.The proposed flux observer can accurately observe the motor flux.In Chapter 5,due to the influence of inverter dead time and high-order harmonic flux in the air gap,there are a large number of high-order harmonic components in phase currents.To reduce the loss of the FPMSM,Chapter 5 further discusses how to suppress the high-order harmonic current in the FPMSM.Firstly,this chapter proposes a voltage equation of FPMSM including high-order harmonic components.Then,to suppress the 7th and 9th harmonic currents in the FPMSM,a multi synchronous rotation frame transformation algorithm（MSRFTs）based on the FPMSM is proposed in this chapter Through the proposed MSRFTs algorithm,the 7th and 9th harmonic components in phase current can be converted into DC components in 7th and 9th harmonic frame,respectively,so that the high-order harmonic component in the phase current can be successfully suppressed by PI controller.In conclusion,this paper has researched the FPMSM drive system from the perspective of high efficiency,high energy density,and fast response,and verifies the feasibility of the proposed algorithm through experiments.