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

Current-source converter is paid more and more attention due to its high reliability which is suitable for electrical vehicle charging applications. In order to achieve popular 800V or promising 1000V fast charging, cascaded current-source converter with higher output voltage capability is proposed in recent years. However, present control strategy for cascaded current-source converter is susceptible to unbalanced grid voltage which is common in practical EV charging applications. In order 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. Proposed strategy could coordinated 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 more balanced and sinusoidal input current with target voltage output. Both Simulink simulations and hardware-in-the-loop (HIL) tests demonstrate the effectiveness and superiority of the proposed coordinated control strategy.