Coordinated Control Strategy for Cascaded Current-Source Converter Under Unbalanced Grid Voltage

Current-source converter is getting more and more attention due to its high reliability, which is suitable for electrical vehicle charging applications. To achieve popular 800 V or promising 1000 V fast charging, a cascaded current-source converter with higher output voltage capability has been proposed in recent years. However, the present control strategy for cascaded current-source converter is susceptible to unbalanced grid voltage, which is common in practical EV charging applications. To mitigate the unbalance and distortion of grid-side current and achieve reference voltage output under the unbalanced grid voltage, a coordinated control strategy for cascaded current-source converter is proposed in this article. The proposed strategy could coordinate and regulate the grid-side current, dc-link current and output voltage based on the degrees of freedom in front-stage and back-stage converters to maintain a more balanced and sinusoidal input current with target voltage output. Both Simulink simulations and hardware-in-the-loop tests demonstrate the effectiveness and superiority of the proposed coordinated control strategy.