Inductive Coupling Type Composite Device with DC Power Flow Control and Fault Current Limiting Functions

As an effective means to solve the problem of large-scale access and consumption of renewable energy, the high-voltage flexible DC grid has become one of the important development directions of the future power system, but it also makes the problems of power flow control and fault protection more prominent. In order to overcome the above problems and improve the stability of the system, this paper proposes an inductively coupled composite device with dual functions of DC power flow control and fault current limiting. First, the topology of the composite device is proposed; This topology adds a current-limiting branch that can share coupled inductors on the basis of the traditional DC power flow controller. Secondly, the working principle, theoretical derivation and control strategy of the DC power flow function are analyzed in detail. Thirdly, based on the current limiting action sequence proposed under fault conditions, four different periods of steady state, current limiting, fault removal and energy discharge are further analyzed. The effect of coupling inductance and the calculation of DC fault current in various periods are studied. Finally, a four-terminal DC power grid model is built on MATLAB/SIMULINK simulation software. The simulation results show that the proposed topology achieves good power flow control and short-circuit current suppression by sharing coupled inductors, and shortens the fault current removal time under short-circuit fault conditions. Therefore, the stability of the system is improved while ensuring economy. © 2023 Science Press. All rights reserved.