A Generalized Virtual Synchronous Generator Control Strategy of Multi-Terminal HVDC System for Both AC and DC Grid Support

A voltage source converter (VSC) in High Voltage dc (HVDC) transmission system is conventionally controlled for dc voltage stabilization, without extra consideration to ac system stability. However, the modern grid is increasingly penetrated by renewables through power electronic converters, the frequency of ac system asks for more support due to lack of inertia and damping. This paper proposes a generalized virtual synchronous generator (VSG) control strategy for both primary control of dc voltage and ac frequency, which is implemented in receiving-end VSCs in Multi-Terminal HVDC (MTDC) systems. Firstly, the topology and VSG principle of the VSC-MTDC are introduced, and the inner loop control strategy and additional frequency control strategy are analyzed. Secondly, the connection between dc voltage and ac frequency is established through VSG, so that VSC-MTDC can provide inertial support for ac power grid and improve frequency stability. Finally, a comparative simulation is carried out in a five-terminal MTDC system, and the simulation results verify the effectiveness of the proposed control strategy.