HVDC shunt tap based on series-input parallel-output DC-AC multi-module VSCs with DC voltages balancing

Conventionally, tapping-off a small amount of power from an HVDC transmission line to a three-phase local network can be achieved using a DC-to-AC voltage source converter (VSC) followed by a step down transformer. In order to obtain the high-voltage ratings required in the HVDC systems, semiconductor devices should be connected in series. Hence, careful design to ensure dynamic voltage sharing between switches is necessary. In this paper, DC-AC multi-module VSCs (series-input parallel-output) along with an input-voltage balancing technique are employed as an alternative solution. The advantages of the proposed architecture against conventional system are also highlighted. A Simulation study is carried out to show the effectiveness of the proposed architecture and to validate the proposed voltage balancing technique.