Performance of a self-commutated BTB HVDC link system under a single-line-to-ground fault condition

This paper deals with a self-commutated back-to-back (BTB) high-voltage direct-current (HVDC) link system for the purpose of power flow control and/or frequency change in transmission systems. Each BTB unit consists of two sets of 16 three-phase voltage-source converters, and their ac terminals are connected in series each other via 16 three-phase transformers. Hence, the BTB unit uses totally 192 switching devices capable of achieving gate commutation. This results in a great reduction of voltage and current harmonics without performing PWM control. Simulation results verify the validity of the proposed system configuration and control scheme not only under a normal operating condition but also under a single-line-to-ground fault condition. Index Terms--BTB HVDC link, multiconverters, power flow control, single-line-to-ground fault, unit capacitance constant.