High Power CSI-Fed IPM drive System Control with Minimum DC-Link Current

In high-power current-source inverter (CSI) fed drives, reduction of losses in semiconductor devices and dc-link inductor through the dc-link current minimization is one of the primary goals. In this paper, a control strategy for the high power CSI-fed interior permanent magnet (IPM) drive is proposed for this purpose. This control strategy keeps the dc-link current at minimum level without exceeding the motor and drive operating limit. The proposed strategy includes two control methods based on field oriented control scheme of the CSI-fed IPM drive. These control methods are a maximum modulation index control scheme and an optimal stator current angle algorithm. In case of the modulation index control scheme, it is found from the relation between the dc-link current and the modulation index that the dc-link current can be reduced by setting the inverter modulation index to maximum value. In case of the optimal stator current angle algorithm, the relationship between the stator current angle and the dc-link current is first investigated thoroughly. Based on this analysis, the dc-link current can be kept as low as possible without exceeding the voltage operating limit of the motor. This can be achieved by choosing the proper stator current angle based on motor stator voltage limit. As a result of the proposed control strategy, the dc-link and switching devices loss are reduced. The effectiveness of the proposed control strategy is evaluated by both simulation and experimental results. The complete drive is implemented in real time using 10 kW CSI fed drive system with 8.7 hp interior permanent magnet synchronous motor.