| As a bridge connecting transmission network and power users,distribution network is the most critical link that affects power supply reliability and directly affects user experience.With the proposed goal of "double carbon",distributed power will be connected to the distribution network on a large scale,forming an active distribution network.The large number of distributed power sources and the complex and changeable operation mode change the fault characteristics of the distribution network,and the traditional fault handling system is difficult to apply.At the same time,the complex topology structure of the distribution network and the timing error of the measuring device make it more difficult to deal with the fault.Therefore,this paper proposes a new fault handling scheme of active distribution network which integrates automation and relay protection.Aiming at the problem of fault section location in active distribution network,a method of fault section location in active distribution network based on ascending linear programming is proposed.Based on the idea of state approximation and the theory of minimum fault set,a new objective function suitable for integer linear programming is constructed.The multi-point fault section location problem is transformed into a 0-1 integer linear programming problem with highly sparse coefficient matrix by increasing dimension,which improves the reliability of section location results.The simulation results show that this method has certain fault-tolerant ability,is not affected by distortion type,and the solving speed is fast.Aiming at relay protection problems of photovoltaic power supply connected to distribution network along the line,a multi terminal differential protection method based on positive sequence current active component is proposed.Firstly,the access mode,control strategy and fault equivalent model of photovoltaic power supply are introduced.The longitudinal differential protection has absolute selectivity,but the measuring device of distribution network does not have synchronization.The active component of positive sequence current can be used to form protection,which can avoid the influence of the measuring device synchronization error within a certain range.Aiming at the fault location problem of PV power station connected to distribution network by T connection,a two-terminal fault location method is proposed.The relative position relation between the fault point and the grid junction of the photovoltaic power supply is determined by the voltage and current relation in the fault positive sequence additional network.According to the positive sequence voltage and current,the fault location equation is formed,and the electrical volume at multiple times is used as the data source for regression calculation.Aiming at the fault location problem of photovoltaic power supply connecting to distribution network along the line,a new fault location method of active distribution network based on multi-source information fusion was proposed.The fault location was realized by comprehensive use of positive sequence voltage,current amplitude,active power and reactive power.According to the characteristics of the fault line,the relationship between the different electric capacities after the fault is studied.In order to reduce the requirement on the synchronization of measuring device,the voltage and current phasor are relaxed,and the expression of only voltage and current amplitude is obtained,and the fault location problem is transformed into an optimization problem.Aiming at the fault recovery problem of active distribution network,a two-stage fault recovery method is proposed.The loads are divided into primary,secondary and tertiary loads according to their importance.The weight coefficients of the corresponding objective functions of the three loads are also different to ensure the priority recovery of important loads.The first stage uses the main network to restore power supply,reducing the possibility of misoperation;If the full load cannot be recovered in the first stage,the second stage of fault recovery is entered,and distributed power supply,on-load transformer adapter and reactive power compensation device are considered for fault recovery. |
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