Transient Voltage Security Assessment for the High Renewable Power-Penetrated UHVDC Sending-End Power Grid

The UHVDC sending-end power grid with high proportion of renewable energy has serious transient voltage stability problems. Firstly, the structure of renewable power systems and the overvoltage protection logic of the convertor-based renewable generators are introduced. Then, the transient overvoltage characteristic of the high renewable power-penetrated UHVDC sending-end power grid under the DC blocking fault and the commutation failure is analyzed. And the mechanism of renewable generator cascading overvoltage tripping is analyzed in the meantime. On this basis, the transient voltage security index system based on the multiple-two-element table, consisting of the local index for a single node and the global index for the whole system, is established under the single fault and the multiple-fault set respectively. Finally, the effectiveness of the proposed indexes is shown by some case studies of Qinghai Power Grid in China.