Analysis of power flow transfer characteristics and stability improvement method of DC grid considering converter’s safety boundary

In order to analyze the impact of power flow transfer of the DC grid on safe operation, this paper studies the calculation methods of power flow transfer of the DC grid under master–slave control and droop control, including the calculation of power flow transfer in line disconnection situation and converter power changing situation. Through the proposed calculation methods, by considering the safety boundary constraints of the converter station based on the PQ power domain, the impact on the safe operation of a complex DC grid when power flow transferring is analyzed. Finally, to solve instability caused by the power flow transfer, a virtual impedance-based method is introduced to increase the safety boundary and enhances the stable operation ability of the system. Finally, the simulations of an 11-terminal CIGRE DC system established in PSCAD/EMTDC software verify the correctness of the proposed method. 11This work is supported by Cloud energy storage framework-based AI dispatching strategy of renewable energy integration and contingency response (5100-202199274A-0-0-00).