Direct Torque Control Of Matrix Converter-fed Permanent Magnet Synchronous Motor Drives

Matrix converter fed permancent magnet synchronous motor dirve system(MC-PMSM) received much attention in the process of the high-end equipmentmanufacturing nationalization due to their advantages like high power desity, highoperating efficiency, fast dynamic response, etc. However, the conventional directtorque control (DTC) of MC-PMSM always suffers the problems of low input-currentquality, large torque and flux ripples and unfixed switching frequency. To slove aboveproblems, this paper proposes a theoretical system which is named as MC-PMSMevaluation system, and also proposes three novel DTC strategies based on the theoy.The MC-PMSM evaluation system is proposed in this paper. A Unified modelingof MC and PMSM is carried out, and a series of different expressions of theMC-PMSM evaluation system are established, such as evaluation fuctions, impactfactor and enhanced swithing tables. The MC-PMSM evaluation system revealsnonlinear mapping relationships between the all MC switching states and the changerate of the torque and flux in the motor-side and the change rate of the input charge inthe grid-side. This proposed theoy lays the foundation for the novel DTC strategiesA novel DTC strategy of MC fed PMSM drives based on master and slavevectors is proposed. Based on the evaluation functions, the control effect of MC activevector on the change rate of torque and flux of PMSM is analysed, a MC switchingtable is established, and a novel duty cycle control method using master and slavevectors is proposed. The proposed strategy can allocate the multiple swithing states ofMC rationally and achieve fast dynamic response and smooth steady-stateprofermances.And then, a novel DTC strategy of MC fed PMSM drives using duty cycleoptimization is proposed. Based on impact factors, the process of the duty cyclecalculation in the strategy of master and slave vectors is optimized, and a very simpleduty cycle control strategy is proposed. Then, a comparative discussion about thedifference between the novel strategy of master and slave vectors and the novelstrategy of duty cycle optimization is carried out. The proposed strategy of duty cycleoptimization is a reasonable trade-off method, which has merit of easy to compute,robustness, high torque control performance, etc. Finally, the paper proposes a novel DTC strategy of MC fed PMSM drives basedon the optimal vetor. The mapping relationships between the all MC switching statesand the change rate of the torque and flux in the motor-side and the change rate of theinput charge in the grid-side is analysed by the enhanced switching tables. Based onthe tables, an optimal selection of switching states can be achieved. The proposedstrategy allows the use of all MC switching states including the rotation vectors, andeffectively controls input and output variables of the matrix converter.An MC-PMSM experiment setup is built to investigate the control performace ofthe conventional DTC strategy and three proposed DTC strategies. The results showthat all of the proposed DTC strategies can solve the problems of conventional DTCstrategy effectively, and they also can maintain the merits of fast torque response, noneed of rotary coordinate, and so on. Therefore, the proposed theory and controlstrategies in this paper are supported and verified.