VSC transmission control under faults

This paper studies the VSC (voltage source converter) transmission control for fault conditions. A small-signal VSC transmission controller considers only small deviations around steady state and in case of faults there would be large overvoltages and overcurrents. An additional fault controller is introduced to reduce transient overvoltages and overcurrents which occur in case of faults. Parallel configuration is used in this model in which current controller is competing with the voltage controller and this enables fast voltage control during steady state and fast current control during faults. The transition between small signal and fault controller is achieved using minimum elements with the modulation angle and magnitude control signals. There is a dedicated fault controller at the rectifier and inverter side. PSCAD is used for the design and testing. Simulation of fault shows low overvoltages and overcurrents.