Calculation of DC Fault Overvoltage Considering the Connection of Renewable Energy at Sending End

Ultra high voltage direct current (UHVDC) will have significant temporary overvoltage (TOV) phenomenon when bipolar locking (BB) and commutation failure (CF) occur at the sending end, and TOV will become more and more serious with the increase of renewable energy sources access in the sending end system. According to the characteristics of the TOV caused by BB and CF and the large-scale renewable energy sources access situation, this paper proposes a unified calculation formula for TOV after the two types of faults occur. Considering the characteristics of the operating conditions of the sending power grid, a typical working condition of bipolar blocking and commutation failure under different renewable energy sources access ratios is constructed to verify the accuracy of the proposed calculation method. The effectiveness and practicability of the proposed method are verified in the actual grid example at the sending end.