Control Performance Optimization Of High-power Permanent Magnet Synchronous Motor In High-speed Region

Permanent magnet synchronous motor(PMSM)has a series of advantages such as high power density and high efficiency,which makes it more and more widely used in the field of rail transit.Traction motors for rail transit generally operate on square-wave modulation condition in the high-speed region.Under square-wave modulation condition,the selection of different control strategies,non-ideal factors(system delay,motor parameter offset),and the fluctuating dc-link voltage will affect the motor output torque performance,which in turn affects the safe and stable operation of the rail transit system.In order to improve the control performance of high-power permanent magnet synchronous motor,this paper takes high-power permanent magnet synchronous motor as the research object,and studies three parts: the control strategy of the single current regulator under the square wave condition,the compensation strategy of the non-ideal factor and the elimination strategy of the torque ripple.The main research contents of the paper are as follows:By analyzing the optimal current trajectories of the finite-speed permanent magnet motor and the infinite-speed permanent magnet motor in the field weakening region,the variation range of the voltage phase angle and the monotonic relationship between the torque and voltage phase angle and the d、q axis voltage within this range are analyzed.Through the derivation,six control strategies based on the single current regulator under the square wave condition are obtained.The stability of these six control strategies is analyzed by means of small-signal modeling,and a comparative analysis of these six single-current regulator control strategies is carried out from the perspective of whether it is necessary to switch the direction of the regulator in the whole field weakening region..Aiming at the problem that the non-ideal factors lead to the decrease of the output torque accuracy of the motor,the influence of system delay and motor parameter offset on motor control performance and the corresponding compensation strategy are analyzed.The research results show that due to the existence of the current regulator,the system delay has no effect on the accuracy of the motor torque output;and the motor parameter offset has a greater impact on the accuracy of the motor torque output.By analyzing the influence of motor parameter offset on motor control variables,corresponding parameter compensation strategies are proposed for six single current regulator control strategies.Aiming at the problem of secondary pulsation in the motor output torque caused by the secondary pulsating voltage of the DC side of the rail transit traction converter,by analyzing the relationship between the pulsating component in the torque of the permanent magnet synchronous motor and the pulsating components in the d and q-axis currents,an improved closed-loop frequency compensation strategy is proposed.Compared with the traditional open-loop frequency compensation method,the proposed method can eliminate the ripple in the torque by extracting the ripple components in the d and q-axis currents and design the corresponding closed-loop frequency compensator,which further improves the output accuracy of the torque..By building simulation models and experimental platforms,simulation and experimental verification of different single current regulator control strategies,compensation strategies for non-ideal factors and torque ripple elimination strategies are carried out.Simulation and experimental results confirm the accuracy of the above theoretical analysis.