Application of ZnO varistor protection to capacitors of artificially commutated inverter in MTDC system

The dynamic analysis of a mesh-type multiterminal HVDC (MTDC) transmission system including an artificially commutated inverter (ACI) with varistor-protected series capacitors is carried out using digital simulation techniques. The study shows that the varistor protection is feasible and improves the performance of normal rated inverters which connect weak AC systems. It reduces the magnitude of the dynamic overvoltage and the peak direct current at the ACI during abnormal conditions, resulting in significantly improved dynamic performance for the MTDC system.<
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