The Research Of Flux Weakening Control Strategy For PMSM

The permanent magnet synchronous machine(PMSM)is applied in the area of transportation more widely due to its several advantages like high power density,high efficiency,etc.On the application areas of high speed railway and electric vehicle which require wide speed range,flux weakening(FW)control technique is more important than other areas.PMSM always operates at constant torque mode below rated speed and constant power mode above rated speed.Because the back electromotive force generated by high-speed rotor under constant power mode will cause the voltage saturation of inverter,FW current of stator is needed to assure controller works in the linear region.FW control technique can significantly improve the highest speed of PMSM without changing the machine structure and inverter capacity.Therefore,it is very meaningful to research on the FW control strategy of PMSM.The thesis aims at solving the problem of PMSM such as voltage saturation and torque instability at high speed range.Some new algorithms are proposed and simulations as well as experiments are done to verify the effectiveness and stability of these algorithms.The main content of this thesis are listed below.The first chapter summaries the research of FW control algorithms in the past two decades and analyzes their different application backgrounds,merits and demerits.The second chapter introduces the math model of PMSM and FW operation principle.It provides theoretical foundation for proposed FW control algorithms.The third chapter proposes new torque feedforward FW control algorithm and includes three different torque and stator flux linkage command adjustment algorithms and three different current command online lookup algorithms.The fourth and fifth chapter verify the proposed algorithms in the third chapter by simulation and experiment respectively.