Research On Current Control Strategy Of High Speed Permanent Magnet Synchronous Motor Based On Discrete Model

With the high efficiency and high inertia ratio characteristics,permanent magnet synchronous motor(PMSM)has been widely applied in electric vehicles,heavy industrial machinery and other industrial occasions.High-speed interior permanent magnet synchronous motor(IPMSM)gets more attention because of its smaller,lighter weight,higher power density.But the maximum fundamental frequency makes the control more difficult.The current control performance has been deteriorated by the d-q axis current cross-coupling,the control system delays,the errors introduced by discretization method approximation,and the motor parameters variations.Based on these issues,the main research works include the following aspects:Firstly,the characteristics of the IPMSM voltage equation are analyzed at high speed,and the discrete model of IPMSM driven by an inverter is constructed from the flux linkage.The delay model is established for the delay of digital control system.The discrete model of IPMSM and the delay model are combined,which lays the foundation for the design of current controller.Secondly,the current controller based on surface PMSM is analyzed through the zero-pole distribution of closed-loop system.The performance of discrete current controller which designed on the traditional PI,indirect design and direct design is discussed.Based on the discrete model of IPMSM controlled system,the improved discrete current regulator is designed through the direct design method,which solves the problems of control delay,indirect discretization error and cross coupling,and improves the current control performance.The performance of the experiment is verified by simulation experiment.Thirdly,the zero-pole cancellation and damping coefficients of the closed-loop system are affected by the temporal variation of the IPMSM parameter,and the current control performance is degraded.Therefore,in order to improve the system adaptability and robustness,the discrete sliding mode control is introduced on the basis of the improved discrete current controller.With the sliding surface designed,the sliding mode arrival process is eliminated to ensure the global robustness of the system and verified by simulation experiments.Finally,a high-speed PMSM control system experiment platform is set up with DSP28335 as the core of control,and the control strategy is verified on this platform.The results show that the proposed control strategy can effectively solve the problems existing in current control at high speed and improve the performance of current control.