Research On Strategies Of Current Oscillation Suppression For PMSM In Flux-weakening Region

The permanent magnet synchronous machine(PMSM)has been widely applied in industrial transmission systems due to its high power density and efficiency.The flux-weakening control aims to widen the speed range by reducing the flux level,with constraint from the maximum voltage fed by the inverter.Under the conventional voltage feedback flux-weakening method,the coupling relationship between dq-axis current get stronger with the rising speed,in this case,the current shake and torque oscillation might be introduced into the system.This paper aims to relieve the current oscillation and increase the stability of the system in high speed range.Regarding the motor parameters,two revised flux-weakening schemes are proposed in this paper to solve the problem mentioned above.For motors whose characteristic point locate outside the current limit circle,the single current regulator flux-weakening method is adopted to give the q-axis voltage on the basis of the d-axis voltage,in this case,the current oscillation is relieved cause the q-axis output voltage saturation is eliminated.For motors whose characteristic point locates within the current limit circle,the operating point is switched from the current circle to the Maximum Torque per Volt(MTPV)trajectory,this method could reduce the equivalent gain of the q-axis current regulator,in this case,the current oscillation is relieved and the stability is improved.To testify the schemes' performance,simulations are implemented in Matlab/Simulink environment.The single d-axis current regulator flux-weakening method is testified on the experimental platform.The results show both the revised strategies could reduce the current oscillation and improve the stability of the drive system in flux-weakening region.