| With the rapid development of the national economy and the continuous increase in the total electricity consumption of the whole society,the existing structure of the power grid has been greatly challenged.As a typical high-speed development of urban power grid,Hefei Power Grid has an unbalanced distribution of load centers and power generation centers.Because of the coexistence of heavy-duty and light-loaded grid equipment,it is difficult to fully utilize the system's existing transmission potential.The construction of new transmission channels is difficult and requires a certain engineering cycle.The transmission bottleneck caused by heavy-duty lines is becoming a weak link in the existing grid structure,and the ability of the system to withstand the risk of failure is seriously reduced.It also affects the overall power supply level and safe and reliable operation capability of Hefei Power Grid.Unified power flow controller(UPFC)is a highly controllable flexible AC transmission device,which can optimizes power flow distribution,taps potential of transmission,realizes dynamic co.mpensation of reactive power,and improves the safe and reliable operation level of the power grid.Based on the steady-state application of UPFC in the system,this paper studies the impact of UPFC on system reliability and available transmission capacity and how to more effectively play the function of UPFC by optimizing the configuration.Considering the standby structure and operation protection principle of doublecircuit UPFC and transforming the outbound communication system into UPFC subsystem,the five-state reliability model of double-circuit UPFC is established and the operation probability of each state of UPFC is calculated based on the traditional fourstate UPFC reliability model.Node injection power model for UPFC and its operating states are established and on the basis of traditional reliability evaluation,random fault simulation of UPFC and parameter adjustment of specific operation mode of UPFC after fault are added to study the comprehensive influence of UPFC on system reliability.Considering the static security constraints of power system,an optimization algorithm is used to solve the influence of UPFC on the available transmission capacity of power system.Considering the system reliability,available transmission capacity and investment cost of UPFC,an optimal configuration model of UPFC is established.The improved multi-objective particle swarm optimization algorithm is used to solve the capacity and location of UPFC and the best compatibility solution is selected from the Pareto solution set by using the method of fuzzy satisfaction.Taking Hefei power grid with unbalanced power flow distribution as the research object,the improvement ability of UPFC to system reliability and available transmission capacity is verified,and the effectiveness of UPFC multi-objective optimal allocation model is verified to determine the optimal allocation scheme of UPFC in southern Hefei power grid.By installing UPFC in Hefei Southern Power Grid,the problems of N-1 and uneven distribution of power flow in Southern Power Grid can be effectively solved. |
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