Common-Mode-Voltage-Reduced Model-Predictive Control Scheme for Current-Source-Converter-Fed Induction Motor Drives

Abstract

Common-mode voltages (CMVs) in a motor drive system could damage the motor insulation and induce destructive bearing current, especially at medium-voltage (MV) level. Various reduced CMV space vector modulation (RCMV SVM) methods have been proposed for current-source converter (CSC)-fed motor drives. However, no matter what kind of RCMV SVM methods, the CMV peak value can only be reduced to no larger than summation of half peak values of capacitor phase voltages at both rectifier and inverter sides, since only zero-state vectors with higher CMV values are eliminated. In this paper, a CMV reduced model-predictive control (RCMV-MPC) is proposed to further mitigate the CMV peak value through selecting optimal space vectors for both current-source rectifier and current-source inverter simultaneously. A novel unified cost function is developed to realize both rectifier- and inverter-side reference tracks and CMV peak value further reduction at the same time. With RCMV-MPC, the CMV peak value in a CSC-fed induction motor drive can be further reduced inside a calculated CMV peak value limitation. In fact, the CMV peak value of RCMV-MPC can be reduced to nearly 60% of that in existing zero-state vector selection-based RCMV SVM methods. Besides, satisfactory performance on reference tracks, especially during transients, is also guaranteed based on the unified cost function. Simulation results in a high-power MV CSC-fed IM drive (1 MW, 4160 V), and experiments in a low-power prototype (5 kW, 208 V) verify the effectiveness of RCMV-MPC.