Research On Voltage Control Strategy Of Distributed Network With High Penetration Of Photovoltaic Power Supply

With the global energy shortage and environmental pollution becoming more and more serious,renewable new energy has attracted extensive attention from governments and all sectors of society due to its clean,pollution-free and abundant resources.Distributed photovoltaic power generation is one of the most potential forms and plays an important role in China's future energy structure.China attaches great importance to the photovoltaic industry and has issued a series of policy documents to promote its development.At present,the installed capacity of photovoltaic power generation in China has been the first in the world for many years.However,the output of distributed generation system is stochastic,fluctuating and intermittent,so large-scale PV Grid-connected system has a great impact on the operation control of the system.One of the most prominent problems is the change of line power flow characteristics,resulting in local voltage elevation or even more limited.In view of the above problems,it is of great significance to study the voltage control method suitable for high permeability photovoltaic access to distribution network to improve system reliability and photovoltaic consumption capacity.This paper starts with the research on the mechanism that affects the voltage distribution of the distribution network,and analyzes the different access,location and form of photovoltaic power.Finally,the influence of PV grid connected system on the distribution network voltage distribution is verified by an example,which provides a theoretical basis for the subsequent voltage control methods.Based on the reactive voltage regulation capability of photovoltaic power supply,this paper proposes a centralized control method and a hierarchical distributed control method respectively.In view of the difficulty of establishing accurate network model for medium and low voltage distribution network,a centralized voltage control method without model dependence is proposed.A convolutional neural network model is built,which is trained by the historical operation data to fit the functional relationship between node voltage and node injection power.For the pre-trained network model,the disturbance method is used to obtain the node voltage sensitivity and coordinate each controllable photovoltaic power supply for reactive voltage control.Finally,the accuracy of the fitted voltage regulation function and the effectiveness of the control method are verified on the MATLAB.Due to the fact that distribution network node number is large while measurement devices cannot achieve comprehensive monitoring for whole distribution situations.Therefore,this paper proposes a voltage hierarchical perception and regulation method based on multi-agent system architecture.Based on the topological structure of the network and the access location of DG,the distribution network is divided into three layers: node-line-system.The voltage sensing algorithm uses the measurement and interaction capability of each layer to realize the voltage sensing of the whole network through distributed computing.The voltage regulation strategy takes advantage of the bottom autonomous control and inter-layer coordinated control and give full play to reactive power regulation ability of distributed photovoltaic power supply to realize the hierarchical control of distribution network voltage.