Research On The Calculation And Control Of Loop Closing Current Base On CIM

The distribution network is the "last mile " connecting the power system and users,and its power supply reliability directly affects users’ power experience.The 10 k V distribution network loop closing technology can reduce user outage time and improve user satisfaction.However,excessive loop closing current may cause the closing operation to fail,and even lead to more serious power outages.This is also the reason for the conservative attitude of the on-site staff towards the loop closing operation and the low rate of loop closing.In order to reduce the risk of loop closing operation,this paper studies the topology analysis method of loop closing circuit in power system,the calculation method of loop closing current and its comprehensive control strategy.The topology analysis algorithm of power system based on CIM model is studied.Firstly,the characteristics of CIM model based on IEC61970 standard are analyzed.Then,according to the same Voltage Level field of switches in the same voltage level in CIM model,an improved topology analysis method is proposed based on the traditional node fusion method.The switches are grouped by the Voltage Level field,and the connection points of each group of switches are fused by the node fusion method to form topology nodes;Finally,the efficiency of the proposed algorithm in topology search is compared with tree search method,incidence matrix method and other commonly used topology analysis algorithms.Practical examples show that the proposed algorithm has simple logic,clear physical meaning,lower time complexity and higher efficiency of topology search.The calculation method of the steady state and transient loop closing current of10 k V medium voltage distribution network is studied.Firstly,on the basis of topology analysis,a "Three-stage" steady-state loop closing current calculation method suitable for complex distribution network is proposed: 1)Based on Newton power flow algorithm with optimal multiplier,the main power flow is calculated,and the voltage and phase angle of two feeders are obtained;2)Based on the forward backward sweep method,the power flow of the two feeders is calculated to obtain the voltage phase difference between the two sides of the loop closing point;3)Based on the node impedance matrix of the main network and the topology search of the closed loop,the equivalent impedance of the closed loop is obtained,and the current of closing loop branch and non-closing loop branch are calculated by the superposition theorem.Secondly,based on Thevenin equivalent circuit of closing loop,the mathematical model of closed loop transient process is established,and the closing loop impulse current is analyzed.Finally,the influence of transformer tap adjustment and capacitor bank switching on the closing current is analyzed.The conclusion that the equivalent impedance of the loop closing circuit is a quadratic function of the inverse ratio of transformer is obtained.The simulation shows that the proposed loop closing current calculation method is suitable for complex distribution network and meets the needs of practical engineering.A comprehensive control method of closing loop current based on particle swarm optimization is proposed.Firstly,considering the safety and economy of the loop closing operation,the mathematical model of the comprehensive regulation of the loop closing current is established to minimize the switching action of transformer taps and reactive power compensation capacitor banks;Then,the constrained optimization problem is transformed into unconstrained optimization problem by penalty function method,and the independent variables are divided into control variables and state variables,which simplifies the process of solving the objective function;Finally,particle swarm optimization is used to solve the current optimization problem.In view of the poor ability of the basic PSO in the later stage,the particle swarm optimization algorithm is improved,that is,the swarm,whose position will not change in the later stage,is replaced by a new swarm for the particles.The simulation verifies the effectiveness of the proposed regulation strategy.