Analysis method of transient overvoltage caused by DC bipolar blocking based on second-order equivalent circuit

Abstract In the wind power transmission system via DC under the support of a weak grid, there is a transient process on the same time scale as the fault duration. The existing calculation method of temporary overvoltage based on surplus reactive power does not consider the transient characteristics of the system, and there is a large error in the calculation of temporary overvoltage under a weak grid. In this paper, research is carried out through theoretical derivation and simulation verification. Firstly, the AC grid near the sending end is reasonably simplified and equivalent to a second-order circuit, and the analytical expression of the transient voltage is given. Then, combined with the actual physical process, the physical meanings of the transient component and the steady-state component in the total transient voltage response are respectively discussed. Finally, based on the Matlab/Simulink simulation platform, a typical system model of wind power transmission via DC is built to verify the correctness of the proposed method. The results show that the equivalent second-order transient response method proposed in this paper has high accuracy in describing the short-term temporary overvoltage characteristics and calculating the overvoltage peak value after the DC bipolar blocking fault.