Analytically Assessing the Effect of Strength on Temporary Overvoltage in Hybrid Multi-Infeed HVdc Systems

In hybrid multi-infeed HVdc (HMIDC) systems comprising both voltage-source and line-commutated converters’ inverters, the strength has a significant effect on the temporary overvoltage (TOV). However, this effect has always been assessed by the simulated approach in earlier works. It is unable to provide the sufficiently theoretical perspectives and also time-consuming as onerous electromagnetic transient simulations are required. Therefore, in this letter, the mathematical expression of the TOV is first derived as the analytical function of the hybrid multi-infeed interactive effective short-circuit ratio (HMIESCR) strength index. This derivation is achieved by using the quasi-steady-state analytical model of HMIDC systems with the interinverter interactions considered. Then, the derived expression is utilized for analytically assessing the effect of the HMIESCR on the TOV versus various system parameters and operation variables. Compared to the simulated approach, the proposed analytical approach here can offer more sufficiently theoretical perspectives and is also more efficient as simulations are no more required. Finally, the experimental results of a hybrid tri-infeed HVdc test system based on the hardware-in-the-loop platform validate the analytical approach.