A Control Strategy for Suppressing the DC Overvoltage under the Fault of DC Power Grid

Unbalanced power in DC power grid causes DC overvoltage, which damages the capacitors, IGBT and other devices, so it is essentially important to suppress the DC overvoltage. Aiming at the problem of DC overvoltage suppression, this paper proposes a new control strategy to suppress the rise of DC voltage by adding DC voltage signal to traditional constant AC voltage controller. Firstly, the mechanism of DC overvoltage is studied, and the relationship between the DC voltage and the unbalanced power in DC power grid is qualitatively and quantitatively analyzed according to the law of energy conservation. Then the relationship between the DC voltage and AC voltage is obtained, and an additional DC voltage control strategy is proposed for constant AC voltage control to suppress the rise of DC voltage. Based on the PSCAD/EMTDC, the simulation model of four terminal VSC-HVDC is built. In the case of blocking fault at the receiving end, the effectiveness of the proposed control strategy is verified.