Research on stability margin enhancement for low-voltage multi-terminal DC system based on additional damping control

Abstract

The low-voltage multi-terminal DC system is becoming an important form of the distribution network in the future. However, the system stability margin will be weakened by the negative impedance characteristics of the DC network. The additional control method by using Lyapunov theory has become a feasible solution to improve system stability. However, the traditional way of using empirical values to design parameters of the weighted matrix cannot ensure that the solved feedback law is optimal, resulting in the limitation of control performance. In order to solve this problem, the dominant mode which determines the system stability margin is studied. Then an additional damping control method is further proposed, and its feedback law is designed and further improved by optimising the parameters of weighted matrix Q, based on the improved particle swarm optimisation algorithm, meanwhile, the optimal configuration of the dominant mode is used as the target for the parameter design. Finally, the proposed method is tested and verified, and the results show that the proposed method can significantly improve the system stability margin and dynamic performance with small control costs, and ensure the constant voltage of the DC network and safe system operation under disturbances.