Along with the successive operation of high-capacity HVDC transmission projects, the voltage stability level of multi-HVDC-feed power system is decreasing continually. AC and DC faults can easily lead local grid or whole system voltage instability or even voltage collapse. Transient voltage stability has become a significant constraint for the stable operation of multi-HVDC-feed power grids. This paper firstly analyses various key factors related to transient voltage instability in the receiving side power grid, and points out the gradual development processes of transient voltage instability in multi-HVDC-feed power system with multi-factor-coupling effect after AC and DC faults. On this basis, the countermeasures which can effectively suppress transient voltage instability and improve the voltage stability level of the receiving end system are proposed. Finally, the effectiveness of the proposed measures is verified by simulation based on a practical grid.
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