Study On Model Predictive Control Strategy For Open Winding Permanent Magnet Synchronous Motor

Open winding permanent magnet synchronous motor(OW-PMSM)can be obtained by untangling the neutral point of stator windings and connecting another inverter in conventional permanent magnet synchronous motor(PMSM).By comparison with PMSM,the topology of OW-PMSM powered by two inverters reduces the requirement of voltage level in single inverter.Besides,multilevel modulation effect and excellent fault-tolerance performance also can be achieved.In all,the advantages of open winding structure and PMSM are inherited in OW-PMSM and it makes OW-PMSM available to the applications of larger capacity and higher power.For OW-PMSM with common dc bus,the volume of system is compressed and the cost is saved.However,in the structure of common dc bus,the flowing path of zero-sequence current exists and the suppression of zero-sequence current should be considered.In this paper,OW-PMSM with common dc bus is chosen as the object of study,and the optimization control strategy of model predictive control(MPC)in OW-PMSM system is mainly studied.The main research of this paper are as follows:(1)In order to solve the problem that the control performance of OW-PMSM in conventional single vector model predictive current control(CSV-MPCC)method is affected by the fixed dead-zone,an optimized model predictive current control considering dead-zone effect(MPCC-DZE)method is put forward.Firstly,the influence of dead-zone voltage vector in CSV-MPCC method is analyzed,and the process of judging dead-zone voltage vector is summarized.Then,the applied time of dead-zone voltage vector related to Inverter2 is redistributed.On the basis of deadbeat predictive current control principal,the variable applied time of dead-zone voltage vector related to Inverter2 can be obtained by using the current information of dq0-axes.As a result,the equivalent number of voltage vectors applied to Inverter2 in one control period is increased to two,which means that the steady-state performance of OW-PMSM system shall be improved.(2)Aiming to address the problem that the control performance improvement of OW-PMSM in CSV-MPCC method is limited by the number of voltage vectors in one control period,a simple model predictive current control based on duty ratio control(MPCC-DRC)method is proposed.In MPCC-DRC method,the optimal voltage vectors corresponding to Inverter1 and Inverter2 can be determined by using fast vector selection method firstly.Then,the applied time of optimal voltage vectors and zero voltage vectors can be calculated in combination of reference voltage prediction model and deadbeat predictive current control principal.In addition,the applied time of zero voltage vectors is reordered to reduce the action times of switching tubes,which means that the switching loss caused by the number increase of voltage vectors can be lowered.As a result,the way of applying duty ratio control to CSV-MPCC method can further enhance the steady-state performance of OW-PMSM system.Finally,experimental tests are finished to compare the control performance of OW-PMSM system in CSV-MPCC method,MPCC-DZE method and MPCC-DRC method,and the results verify the validity and innovation of the proposed methods in this paper.