An Accurate Virtual Signal Injection Control of MTPA for an IPMSM with Fast Dynamic Response

A maximum torque per ampere (MTPA) control based on virtual signal injection for an interior permanent magnet synchronous motor with fast dynamic response is proposed in this paper. A small square wave signal is mathematically injected into the current angle for accurately tracking MTPA points. The extracted derivative of electromagnetic torque is utilized to compensate the initially set current angle to the real MTPA operation current angle. Due to the absence of bandpass and low-pass filters, which are essential in the sinusoidal injected signal scheme, this method shows good dynamic response. By incorporating a modified equation for the torque after signal injection, the steady-state accuracy is also enhanced. The $d$-and $q$-axis current references are obtained through the current vector magnitude and optimal current angle instead of using the torque equation with nominal motor parameters, which guarantees the accuracy of the output torque. The proposed scheme is parameter independent, and no real signal is injected to the current or voltage command. Thus, the problems of the high-frequency signal injection method are avoided. A prototype is set up, and experiments are carried out to verify effectiveness and robustness of the proposed control scheme.