Research on Back-to-Back HVDC Additional Frequency Synchronous Control Strategy Applied to Asynchronous Interconnected Systems.

When regional power grid is asynchronized by high voltage direct current (HVDC) systems, the division of frequency regulation resources and reserve capacity weakens the system’s ability to resist load fluctuation and fault disturbance. With the continuous promotion of electricity market construction in China, the demand of building a unified frequency regulation auxiliary market for the whole power grid is increasingly frequent. In this paper, with the objectives of improving the overall frequency regulation performance of asynchronous interconnected systems and refers to the power transmission characteristics of AC transmission lines. The additional frequency synchronous control (AFSC) strategy of back-to-back HVDC was studied, which enables back-to-back HVDC to automatically adjust the transmission power based on the frequency difference on both sides. Then, taking Luxi back-to-back HVDC of China Southern Power Grid (CSG) as an example, the specific implementation of AFSC strategy is studied, and the effectiveness of the proposed strategy is verified by real-time simulation. Finally, the on-site practical application of this strategy was analyzed.