Improved model-based predictive torque control algorithm with modified modulation index for doubly salient permanent magnet synchronous machines

Abstract

The doubly salient permanent-magnet synchronous machine (DSPMSM) is a new type of brushless machine and has got worldwide concern for some advantages, such as high power/torque density, simple structure, and wide speed range. Due to its inherited doubly salient structure and special working principle, the DSPMSM suffers from severe torque and flux ripple. Although some conventional control algorithms have already found some applications to DSPMSM drive system, their drive performance are not excellent during the operation, e.g. slow dynamic response, large torque ripple especially in starting or low speed. This paper proposes an improved model based predictive torque control (MPTC) algorithm to reduce the torque and flux ripple of DSPMSM. First, it derives the mathematical model of DSPMSM and then obtains its mathematical equations of ABC and d-q coordinate systems. Second, it studies the model based predictive torque control strategy, including optimality and implementation principle. Third, it proposes an improved MPTC strategy with a modified modulation index to increase the drive performance of DSPMSM, such as dynamic response and stable smoothness of torque. Based on this strategy with the modified modulation index, the torque and flux ripple of DSPMSM are reduced obviously, along with controlling the inverter in real-time to minimize the converter switching frequency. Comprehensive simulations validate relevant theoretical analysis.