Research On Power Flow Calculation Of Distribution Network With Distributed Generation

Under the background of global climate warming and fossil energy crisis,it is urgent to explore the technology of replacing traditional fossil energy with new energy.In recent years,distributed power generation technology has been widely concerned and rapidly developed by the international community.On the one hand,the access of distributed power to the traditional power grid injects new vitality into it,which makes the power generation model more abundant,plays a certain auxiliary supporting role to the traditional power grid,and brings huge benefits to people's life and social and economic development,and also conforms to the development concept of green development and low-carbon economy proposed by the state.On the other hand,connecting distributed power to the distribution network also brings many challenges.For example,the traditional power flow calculation methods has been unable to meet the parameter calculation of distribution network systems with various distributed power sources.This paper studies the power flow calculation of distribution network with distributed power,and its main work is as follows:(1)With the access of various types of distributed power sources,there will be many new types of nodes in the process of power flow calculation,which can not be simply regarded as PQ nodes of traditional power flow calculation.In this paper,according to the characteristics of different distributed power sources,their mathematical models are established and divided into different node types,and then the processing methods of different node types in power flow calculation are proposed.(2)According to the characteristics that R / X ratio of line parameters in the distribution network is large,the models of main electrical components,such as lines,transformers,capacitors,loads in the distribution network are established to make them conform to the characteristics of power flow calculation in the distribution network with distributed generation.(3)This paper introduces several common methods of power flow calculation.On the basis of method of forward and backward power flow calculation,a more effective and improved method of forward and backward power flow calculation is proposed to calculate the power flow of the distribution network with PV nodes.This method mainly uses the information of each node of the upstream branch of the PV node to calculate the voltage phase angle and reactive power rate of the PV node in the reverse power generation process.In addition,when there are distributed power sources,faults or network reorganization in the distribution network,the loop network will appear.In this paper,the three parameters of thenodal power equation in polar coordinates are approximately performed linearly,and the nodal power equation is simplified by using the properties of the admittance matrix,and a linear node power equation is obtained.The power flow calculation method based on the method can effectively deal with the power flow calculation of with the weak loop network.Taking the IEEE11 and IEEE33 nodes as examples,the effectiveness and feasibility of the two improved methods are verified.(4)A large number of distributed power sources connected to the distribution network will also have a certain impact on the voltage and power quality of the distribution network.In this paper,the loss value and voltage variation of the distribution network are analyzed from two aspects: the number of distributed power sources connected to the distribution network and the number of distribution network containing weak loop.In this paper,the concept of hierarchical point is proposed,and the weak loop distribution network is decomposed into a pure ring network and a pure radial network connected by hierarchical points.In the ring network,the hierarchical point is used as load nodes or PQ nodes,and the improved Newton method is used.The radial intermediate point is used as a balanced node or V? node,and an improved push-back method is used.This paper is different from the traditional single power flow calculation method,and verifies the feasibility and effectiveness of the method in the IEEE33 node calculation example.