Research on Coordinated Control Strategy of Cascade Voltage Source Converter

To achieve fast charging at the current mainstream voltage levels of 800 V or 1000 V, a cascaded voltage source converter with higher voltage output capability has been proposed. However, current cascaded voltage source converters often adopt two-stage independent control and are susceptible to the impact of power grid voltage imbalance. To reduce control complexity and alleviate distortion and imbalance of grid side currents, this paper proposes a coordinated control strategy for cascaded voltage source converters. This strategy coordinates the degrees of freedom of the preceding and succeeding stages, enabling the converter to have higher voltage output capability without the need for sampling the DC link voltage. Meanwhile, when the power grid is unbalanced, this article adopts a phase voltage reconstruction scheme to ensure the stability and reliability of the coordinated control strategy, making the grid side current and output voltage more balanced and stable. The experiment verified the effectiveness and superiority of the strategy.