Field Weakening Control Of IPMSM Drive System For Electric Vehicle

With the development of vehicle electrification, the R & D investment conducted by the governments and well-known automobile companies is increasing.Without doubt,the environmently friendly pure electric vehicles(PEV) will occupy an important place in the future auto sales market as the result of internal combustion engine vehicles exhaust emissions and the accompanyed hazy weather. The IPMSM has gained the top priority when it comes to the drive motor for the PEV with the inherent merits of higher power density and excellent field weakening performance.However the conventional IPMSM drive system with two current closed-loop PI regulators often suffer saturation fault in field weakening operation.lt is in urgently need to conduct research on field weakening control strategy of IPMSM drive system.The research is significant meaningful to realize the safe and reliable operation of PEV.Due to the wide speed range operation and large current variation of IPMSM,this paper has modeled the IPMSM in synchronous reference frame (d-q axis frame) considering the magnetic saturation and cross-coupling effect between d-q axis based on software Ansoft. It gives the expression of stator current command when IPMSM operates both in constant torque region and field weakening region.In view of limited dc bus voltage of on board inverter, the conventional IPMSM drive system with two current closed-loop PI regulators scheme has the drawback of often saturation in field weakening operation.This paper proposed the self-adaptive single d-axis current PI regulator control when IPMSM drive system enters into field weakening region in order to realize the high-efficient and robust operation over wide speed range.To cope with the parameter dependent of the mentioned single d-axis current PI regulator control scheme, this paper further proposes voltage phase control when IPMSM enters into field weakening region based on the inherent monotone increasing relationship between torque and voltage phase.Considering that the time delay effect of the discrete-time digital control system will intensify the cross-coupling between d-q axis,this paper has presented a compensation method for time delay to make sure the voltage phase control scheme can be applied successfully. The optimal voltage phase is generated by the application of torque PI regulator.The computer simulation results validate the reliable operation of IPMSM drive system based on voltage phase control.