Research on flexible control technology of HVDC

Flexible control technology of HVDC realizes multiarea power transmission and improves operational flexibility of DC transmission. By configuration the connection mode of AC field in inverter station, Yong-Fu HVDC project can realize three kinds of operating scenarios: 1) all of the bipolar power is sent to Guangxi grid; 2) all of the power is sent to Yunnan grid; 3) power of the two DC poles is split and sent to Guangxi and Yunnan, respectively. This is the first HVDC project with the above flexibility implemented in China. In this paper, the realization method of the above flexible regulation is analyzed based on the typical AC field structure. Then a simplified equivalent model of the AC field at the Yong-Fu HVDC receiving end is proposed. With this model, power transmission mode conversion control logic is designed. Finally, a corresponding RTDS real-time simulation system of the HVDC is built and used to verify the power transmission mode conversion under different DC power transmission levels. The theoretical analysis and simulation results provide important reference value for the design and control of Yong-Fu HVDC and similar projects in the future.