Reliability Assessment Of Distribution Network Considering Uncertainty And Islanding Of Distributed Generation

Distributed generations are affected by external factors such as light intensity and wind speed due to their own output.The output power of the power supply has certain uncertainties.When a large number of distributed generations are connected to traditional distribution networks,it changes the structure and operating status of the distribution network,and the power flow in the system flows in two directions,the direction and the size of the power flow change at random,and the network loss and the voltage of the line and the system are also influenced by randomness,so that the reliability evaluation of the power distribution system is more difficult.On the other hand,reasonable choice about the position where distributed power supply is connected to the distribution network can form island and effectively improve the reliability index of load points and the whole distribution system in the distribution network and reduce the probability of load loss caused by the distribution network failure.Based on this,this paper discusses the uncertainty and islanding of distributional power source,and studies the reliability of distribution network with distributed generation.Aiming at the uncertainty of output power of distributed generation such as photovoltaic power and wind power,an improved Latin hypercube sampling algorithm is used to simulate the output of wind speed scenario.And the correlation of multiple random variables is considered.Based on the scene reduction,building power probability model.At the same time,construct load point and line risk index based on risk theory,construct the objective function with the minimum sum of the risk values of all the load points as the objective,and establish the judgment matrix to determine the optimal network access position of the distributed power supply.For distribution network access to distrib,uted generation,drawing on the theory of social structure,the concept of nodes and branches in graph theory is introduced,and the structure of containing networks is divided.On the basis of giving weights to nodes and branches,by constructing the modularity function,under the prerequisite that the priority load of critical load and the maximum load recovery rate are satisfied,an optimal islanding strategy is proposed to combine nodes with the fastest module speed.Based on this,the hybrid assessment method based on the improved least path method and network equivalence method is proposed.The proposed probability model of distribution generation is adopted to calculate the reliability index of each load point and distribution system withdistributed generation and to evaluate the reliability of distribution network with distributed generation.The study shows that the extended Latin hypercube sampling method overcomes the defect of traditional Latin hypercube sampling method that the sampling number must be determined in advance.By constructing the objective function with the load point risk value as a variable and solving the judgment matrix based on a heuristic search algorithm,the optimal network access position of the distributed power supply is determined,so that the influence of the distributed power supply on the system and the load risk is reduced to a lower level after the distributed power supply is connected to the distribution system;the application of community structure theory in distribution system island division provides a new optimal division strategy for distributed generation island division;at the same time,the reliability of distribution network with distributed power supply is evaluated by combining network equivalence method with the improved minimum path method,which simplifies the process of reliability evaluation and improves the indexes such as failure recovery rate,DG effective utilization rate and so on.