Research on the Over-voltage Suppression Strategy for HVDC with New-generation Synchronous Condensers

Under isolated mode of the direct current (DC) transmission system, when bipolar blocking occurs in high voltage direct current(HVDC), the alternating current (AC) system will generate high power frequency over-voltage. Therefore, whether the over-voltage can be suppressed is the key to whether the DC system can operate on an island. The new-generation synchronous condensers can effectively change the grid voltage level. In particular, the AC over-voltage level can be effectively suppressed by a reasonable control strategy. In this paper, a reasonable control strategy is proposed.The new-generation synchronous condenser's reactive power output characteristics were analyzed. Then, the relationship between power frequency over-voltage and short circuit ratio is derived. Simulation results demonstrate the effectiveness of the proposed scheme.