Yunnan power grid asynchronously interconnects with the main grid of China Southern Power Grid by multiple high voltage direct current (HVDC) transmission systems

and the frequency limit controller (FLC) plays a significant role in the frequency control of sending-side system. In the HVDC single-polar block experiment

which is called Chuhui DC system

some HVDC transmission lines operate in an overloaded mode for a long time because of the mismatching between FLC and primary frequency control(FPC). By analyzing the dynamic regulation process of the FLC

regulatory characteristics of different models of the FLC and the coordinated cooperation relationship with primary frequency regulation are clarified. On the basis of that

the paper analyzes the influence of FLC reserve capacity

dead band on the frequency peak and releasing process of FLC by time domain simulation and a frequency modulation strategy of FLC is proposed. Furthermore

the governor parameters are redesigned by eigenvalue sensitivity method for improving the dynamic performance of FPC

which can make the best of FLC on frequency peak restriction and cooperate with primary frequency regulation in the meanwhile to guarantee the rapid release of its adjustment. The results of operation show the availability of proposed strategies.