Research On Voltage Quality Influence And Optimizing Method Of Distributed Generation Connected To Grid

With the increasingly prominent problem of energy shortage and the rapid development of distributed generation technology,the permeability of DG in distribution network is getting higher and higher,which brings a series of voltage quality effects to distribution network.In the paper,the potential impact of DG grid connection on voltage quality is analyzed,and a voltage optimization method is proposed for distribution network with DG.Firstly,the principle of distributed generation technology is introduced and the influence of DG grid-connected voltage level is deduced by mathematical formula.The influence rules of access location,access capacity,power factor and other parameters on voltage problem are pointed out.Taking the photovoltaic power plant in operation as an example,the field measurement and analysis of its voltage quality status are carried out,and the necessity of voltage quality impact analysis is pointed out.The models of wind power generation system and photovoltaic power generation system are built in DIgSILENT,and the correctness of the models is verified.Then,by building a distribution network simulation model in DIgSILENT,the influence of access location,access capacity and power factor on voltage deviation and harmonic voltage is simulated and analyzed.It is pointed out that reasonable DG grid connection can improve the voltage level of system nodes,reduce harmonic effect and improve voltage quality,but unreasonable access may change the monotonicity of voltage distribution,make the voltage of nodes exceed the limit,and increase the harmonics.By simulating the voltage fluctuation of grid-connected photovoltaic system when it suddenly goes off the grid,the law of its influence on the voltage fluctuation is analyzed.Finally,a voltage optimization scheme based on distribution network reconfiguration is proposed for distribution network with DG.The actual distribution network topology is flexible and changeable.The voltage optimization problem is transformed into a pattern recognition problem by finding the mapping relationship between load flow and optimal network structure.Taking the minimum voltage balance index as the objective function,the classification between load flow and optimal network structure of distribution network with DG is carried out by support vector machine(SVM).The problem of difficult expression of SVM output space is solved by constructing a new expression of output vector,and the distribution network topology reconfiguration is completed to realize the voltage optimization of distribution network with DG.The algorithm is validated by taking the distribution network of IEEE 33 nodes as an example.The results show that the algorithm can effectively reduce the voltage balance index,improve the system voltage level,and achieve the purpose of voltage optimization.