Study On The Influence Of Photovoltaic Grid-connection On Distribution Network Voltage And Its Control Method

With the increasingly severe problems of global energy forms and ecological environment,the utilization of clean energy has become a hot research issue worldwide.Photovoltaic power generation is characterized by green and low carbon,in addition to environmental protection,but also should recognize its efficient economic benefits.The randomness and volatility of photovoltaic power generation will have a continuous impact when it is connected to the grid.In addition,in the process of gradual increase of PV permeability,it is easy to cause local voltage overlimit and fluctuation of the distribution network,endangering the stable operation of the system.At present,although many measures have been taken to restrict the off-limit voltage of PV grid connection,they have not solved this problem well.This thesis takes the photovoltaic grid-connected power generation system as the research object,and analyzes the interaction mechanism between the photovoltaic grid-connected power generation system and the distribution network.Based on the characteristics and classification of photovoltaic grid-connected system and the voltage change rule of distribution network generated by grid-connected system,the voltage control method of distribution network including photovoltaic power supply is studied.Firstly,this thesis analyzes the characteristics of photovoltaic cells,establishes its equivalent circuit model,points out that the key factors affecting the non-linear output of photovoltaic power generation are light intensity and battery temperature,and classifies the photovoltaic grid-connected power generation system.On this basis,the influence of photovoltaic access on power flow and power quality of distribution network is analyzed,which lays a theoretical foundation for studying the influence on voltage quality and its control.Secondly,aiming at the development of photovoltaic grid-connection and considering the current development demand of "source network load" flexible interaction.Using a feeder voltage distribution algorithm,and the algorithm can analyze the voltage distribution of distribution network after different quantity of power sources are connected to the grid.Therefore,the voltage distribution when only a certain number of photovoltaic power supply,photovoltaic power supply and controllable load are connected to the distribution network at the same time is analyzed.And then,the voltage distribution rules of different access locations and different access capacities are summarized,and the corresponding simulation verification is carried out.Finally,by analyzing the voltage regulation mechanism of photovoltaic inverter and the network access characteristics of such typical flexible controllable loads as Electric Vehicle,and aiming at the voltage over-limit problem of photovoltaic grid-connection,a voltage regulation method considering load side ev as dispatchable resource and photovoltaic power supply linkage is proposed.Based on the capacity prediction of the dispatchable resources,an optimization model was established to minimize the regulation cost of voltage regulation measures that can participate in voltage recovery.Particle swarm optimization algorithm was used to solve the model and realize the optimal allocation of controllable resources in the system.Two scenarios are constructed according to different meteorological conditions in the example analysis,and the analysis results verify the effectiveness of the proposed method.