Study Of Power Flow Optimization And Control Of AC-DC Hybrid System With DC Power Flow Controller

With the continuous development of flexible high-voltage DC transmission technology,the characteristics of DC power grid,flexible and controllable,and strong adaptability have been rapidly developed.For DC power grid with multiple ring networks,only relying on the converter station cannot achieve effective regulation of the power flow.Because the power flow control degree is insufficient.However,DCPFC is a research hotspot in the field of DC power flow analysis and control,which can realize the rational distribution of the power flow.Meanwhile,as the scale of the power system continues to expand,the optimal power flow perfectly integrates the requirements of the power system for economy and safety,and it has received extensive attention with the decision-making function of guiding the system for optimal scheduling.This article first introduces different types of DCPFC and classifies them,equivalent to its external characteristics,established a steady-state power flow calculation model for DCPFC.A method for solving DC power flow based on equivalent injection power method is used,by adding the influence of the power flow controller to the power flow calculation,the power flow calculation of the DC power grid with the power flow controller is realized.The effectiveness and correctness of the method are verified by a five-terminal DC grid.Second,based on AC/DC system circuit model,considering system economics and safety,a multi-objective optimal power flow model for AC/DC hybrid systems with power flow controllers is constructed.And an alternate solution method based on the combination of interior point method and non-dominated sorting genetic algorithm-II is proposed.The multi-objective optimization problem is divided into two sub-problems to obtain the Pareto optimal solution set.Finally,based on the operation mode and advantages and disadvantages of the master-slave control,voltage deviation control and voltage droop control of the converter station,a generalized droop control method based on optimal power flow is proposed.Aiming at the problem that the converter station cannot completely regulate the system power flow,the coordinated control strategy of the converter station and the DCPFC is proposed.To build the system control architecture based on optimal power flow to verify the proposed control strategy with taking the Zhoushan five-terminal DC power grid as an example on the MATLAB simulation software.