Modeling and Control of a Hybrid Three-terminal HVDC System

With the continuous research of hybrid High Voltage Direct Current (HVDC), the conventional DC voltage control on Line Commutated Converter (LCC) side can not meet the requirements, so it is necessary to study DC voltage control on Voltage Source Converters (VSC) side. Firstly, this paper studies the topology and model of a hybrid three-terminal HVDC system, consisting of LCC and two parallel-connected VSC. Secondly, based on this model, DC voltage control on LCC side is adopted to realize voltage stability of DC system and ensure the stable operation of the system. The other strategy selects one VSC as the control terminal of DC voltage and adopts constant current control for other two terminals. Finally, the simulation is carried out to verify the effectiveness of this strategy by comparing to the conventional strategy, and the hybrid HVDC system which connected to the infinity grid can perform better under the adopted strategy.