Research On Simplified Model Predictive Torque Control For Open Winding Permanent Magnet Synchronous Motor Drive System

With the increases in environmental pollution and global energy crisis,the sustainable and green development has been a national focus,and thus the high efficiency electromechanical energy conversion mode has become a hot area.Due to the features of high efficiency and power density,simple structure,the permanent magnet synchronous motor(PMSM)has been widely applied in industrial application,such as new energy power generation and the electrical power traction filed.Meanwhile,with the fast development of economy and industrial,the power level of PMSM application system increases raplidly,which requires larger capacity of corresponding power converter.However,with the limination of existed switching device,large capacity converter always requires high cost.Therefore,a novel open-winding(OW)permanent magnet synchronous motor(PMSM)system has been received plenty of attention,which is configured by disconnecting the stator winding neutral point of the conventional PMSM and can be fed by two inverters.Thus,the power converter capacity can be reduced effectivelyCommonly,the OW-PMSM system has two typical power supply modes:isolated and commom dc bus supply.Compared to commom dc bus structure,the OW-PMSM fed by two isolated power sources has the advantages of two terminal inputs/outputs,multilevel characteristic,strong fault tolerance,flexible control modes and no zero sequence current,which has been received a plenty of attentions in the past few years and been concerned as a well prospective topology.Moreover,recent years,model predictive control(MPC)has attracted increasing attention due to its intuitive principle and flexibility to include multiple nonlinear constraints,which is most suitable to handle the unique multivariable system constraints and nonlinearities in OW-PMSM system.Therefore,the target of this paper is to make a research of how to make full use of MPC strategy for OW-PMSM system.The main content is organized as follow:Firstly,a simplified model predictive control(SMPC)for OW-PMSM system fed by two isolated power sources is proposed in order to remove the complex tuning work of weighting factors and reduce the calculation burden in the conventional MPC.By researching the cost function of MPC,the inherent effect of the weighting factor is revealed and a tuning guidance of the weighting factor is given.Then,based on the above analysis,control constraints torque and flux in the conventional MPC are converted into an equivalent flux vector for the purpose of eliminating the weighting factor in the cost function.Moreover,a novel prediction strategy and a fast voltage selection scheme are presented to reduce the system calculation burden.As a result,the optimal voltage is selected through only twice evaluations.Furthermore,a switching states distribution strategy is introduced to reduce the switching frequency of dual-inverter.Comparative experiments are conducted to verify the effectiveness of the proposed method.Secondly,a two-vector-based simplified model predictive torque-vector control(TV-SMPC)is proposed to cope with these problems.Firstly,the inherent effect of the weighting coefficient in the C-MPC is revealed.Accordingly,a concept of torque-vector is employed to replace the torque and flux constraints in the cost function in order to eliminate the weighting coefficient and remove the tedious tuning work.More importantly,based on the torque-vector,a simplified two-vector-based prediction strategy is put forward to determine the two optimal voltage vectors and their duty cycles by twice simple comparisons based on twice simple calculations.Comparative experimental studies are carried out to validate the validity of the proposed TV-SMPTC method.In third part,an immediate model predictive flux control(IMPFC)is proposed and implemented in the hybrid-inverter open-winding PMSM to suppress the dc-link capacitor voltage fluctuation.Firstly,a new prediction model of capacitor voltage is established.Then,the voltage control constraints is employed to replace the torque,flux and capacitor voltage constraints in the cost function to eliminate the weighting coefficient.Moreover,a fast three-vector-based voltage selection scheme are presented to reduce the system calculation burden.Comparative experimental studies are carried out to verify the effectiveness.