Improving Fault Recovery Performance of an HVDC Link with a Weak Receiving AC System by Optimization of DC Controls

A problem associated with an HVDC link feeding into a weak AC system is the poor fault recovery performance from commutation failures caused by inverter AC system faults, especially when the receiving AC system is further weakened due to faults clearing. To obtain acceptable recovery performance, the pre-fault DC power transfer capability may have to be limited below the rated DC power. Based on electromagnetic transient simulations, the available power transfer capability of an actual HVDC system is evaluated by considering fault recovery performance of the AC/DC system under specified receiving AC system faults. To increase the available power transfer capability, the optimization of HVDC controls is implemented aiming at obtaining acceptable recovery performance. Simulation results show that the optimized HVDC controls can help to improve fault recovery performance and hence obviously increase the DC power transfer capability.