Study On The Voltage Characteristics And Control Strategy Of Distribution Network With DG

In order to effectively solve the problems of climate warming and energy crisis,China has been vigorously developing new energy power generation technology in recent years.With the proposed goal of "double carbon",the permeability of Distributed Generation in the distribution network has gradually increased.Faced with the voltage quality problem in the process of DG entry into the network,this article analyzes the voltage characteristics of DG entry into the network from three aspects: three-phase voltage unbalance,background harmonic voltage and power fluctuation.Then the voltage control is carried out from two aspects of distribution network structure and compensation device.The structure is to use the node voltage increment to partition the distribution network,so that DG can generate a certain voltage support for the weak nodes in the region.In terms of compensation device,the active and reactive power compensation device is used to compensate the power in the region and alleviate the voltage problem in the over-limit region.The main contents are as follows:Firstly,the type and working principle of DG are introduced,and the position,voltage level and capacity of DG connected to the distribution network are analyzed.Through the field measurement of a photovoltaic power generation company and the national standard limit,the change of photovoltaic grid-connected voltage index is analyzed.Secondly,when the distribution network is in different states,DG access has a great influence on the node voltage.Firstly,the influence of the location and quantity of DG access on the system voltage is analyzed theoretically,and then the negative sequence voltage variation rule of nodes is considered when the distribution network is in the three-phase unbalanced state.When considering the background harmonic voltage of the upper power grid,the harmonic voltage generated by the inverter and the background harmonic voltage are superimposed,and the harmonic frequency that is easy to exceed the standard is obtained.Finally,considering the large fluctuation of DG power,MPPT algorithm is used for voltage control.Next,the voltage variation rule of each node is analyzed when DG is connected to the grid,and voltage sensitivity is used to control the voltage area of the distribution network.By changing the injected power of nodes,the corresponding voltage increment matrix is constructed,and each column vector in the matrix corresponds to a node in the distribution network,and the column vector is clustered to realize the regional division of the distribution network.Different from the single clustering in other literatures,this article uses intra-group linking method,inter-group linking method and Ward method for multiple clustering.When different clustering algorithms are used,individual nodes are divided into different regions.For nodes with overlapping regions,the voltage increment in different regions is determined by using them.Finally,when there is a voltage overlimit in the divided area,the installation position of the compensation device is determined by the comprehensive voltage sensitivity.The larger the value of the node,the more need to be compensated.Then,a voltage control strategy of zone control and interval coordination is proposed,which is regulated by energy storage device,static reactive power compensator,capacitor and on-load regulating transformer.The zone control is an active regulation mode,which adjusts the compensation device in the voltage overlimit zone according to the power flow calculation result.Interval coordination is a kind of dynamic optimization regulation,which uses second-order cone optimization algorithm to reasonably control the output of all compensators and obtain the optimal voltage distribution of distribution network.Finally,a numerical example is given in IEEE33 node distribution network to prove the practicability of the proposed strategy in controlling node voltage.