On Model Predictive Control For Permanent Magnet Synchronous Motor System

Permanent magnet synchronous motor has been widely used in extraction of oil,wind power generation,industrial robots,high precision CNC lathe,and new energy vehicle since it present the features of high energy utilization rate,simple structure,and reliable operation.In many fields,those traditional control methods come into the problem on how to satisfy higher control needs than before in permanent magnet synchronous motor system.Therefore,it is of great practical significance to make an intensive research on new motor control method.Thus in this disertation,the model predictive control based on permanent magnet synchronous motor system will be deeply studied,two kinds of improvement on the model predictive control algorithms are proposed respectively.The major research and novelties can be illustrated as follows:First,the single-loop predictive control which is applied to the surface-mounted permanent magnet synchronous motor control system neglects the effect of external load torque in the whole predictive horizon,which causes imprecise predictive model.A state-prediction model in the form of piecewise function is proposed.Moreover,the amount of calculation is decreased by using a reduced-order model,a two-order linear predictive model is constructed in this paper.Singles-loop predictive controller is designed with this model.The simulation results show that performance of single-loop predictive controller can be improved by accurate modeling of external load torque.Second,in order to reduce computational procedures of space vector pulse width modulation algorithm for three-phase switches commutation,an improved pulse width modulation method is proposed.The conduction duty cycles of three-phase bridges of the inverter are determined by solving three element first order equations firstly,then switching time is solved by conduction duty cycles,Then PWM wave is produced.The simulation results verify the simplification of modulation algorithm does not affect the modulation effect.Third,if enumeration method is adopted to choose ideal voltage vector in model predictive current control,the algorithm will has large amount of calculation and poor real-time performance.To overcome this problem,the simplified voltage vector selection method is proposed.Based on this method,one nonzero voltage vector which is closest to optimal voltage vector is determined initially,then the current control effects of this nonzero voltage vector and zero voltage vector are compared,the control voltage at the current moment is finally selected.The scope of enumeration is reduced from the original 8 basic voltage vectors to 2 basic voltage vectors by resorting to this method.The simulation results prove that the simplified method is the same as the original method in the aspect of voltage vector selection,and the dynamic performance of the current predictive control based on simplified voltage vector selection is superior.