Power Grid Quality Analysis Of Grid-Connected Distributed PV Generation System

From the perspective of environmental protection and energy utilization,there is no harm in photovoltaic power generation,so the government actively develops it.From an economic point of view,due to the support of government policy,investment in photovoltaic power generation is profitable,so the investment enthusiasm increasingly is high.From the point of view of technology,photovoltaic power grid will bring a series of problems to the power grid,which will affect quality of the power grid and may even cause accidents.Therefore,it cannot arbitrarily connect to the grid.On the one hand,it is necessary to develop PV generation system,to pursue economic and social benefits,on the other hand,to ensure the safety of electricity supply,and it is necessary to connect distributed PV system in the planned way.In recent years,this contradiction has become increasingly prominent.This paper aims to help the government,investors(users)and power supply departments to clarify the relationship and ideas through exploring the advantages and disadvantages of photovoltaic power grid connection and power grid quality,and hopefully to guide the work practice.First of all,through the theoretical analysis and practice summary,this article summarized and put forward problems,namely the impact on the after the Grid Quality photovoltaic(pv)'s connecting to the grid,especially the adverse effect.Including: photovoltaic effects on voltage regulation,the influence of relay protection and reliability,and the influence of network loss and network planning,the effect on short circuit and resonant,the impact on the power quality and photovoltaic power generation of unplanned island problem.Then,through the analysis and interpretation of Zhen Jiang Technology New Town's grid connected photovoltaic data,this article has researched quantitative impact of more then one power quality indexes,the photovoltaic grid connected network is studied,Then the quantitative influence of multiple power quality indicators in distribution network is analyzed.According to the measured data,the two indexes,which have the maximum deviation between the flash and the nominal voltage,have the greatest influence,which directly leads to the disqualification of these two indexes.Three voltage balance,frequency deviation,harmonic voltage limit and other indicators are also relatively large,although they are within the range of the national standard but close to the limit value.The impact on other indicators is relatively small.Finally,this paper uses the software platform to simulate the model of a 34 node distribution network,and dynamically verifies the relationship between the input capacity and the power quality index,and the relationship between the access and the power quality index..The following conclusions are obtained :(1)the larger the pv capacity is,the smaller the network loss.(2)the effect of voltage fluctuation in photovoltaic power station operation is significant,and the closer the access point is to the end of distribution network,the greater the impact on voltage fluctuation..(3)the closerthe photovoltaic power station access point is to the end of the distribution network,the better the network damage degree,at least not less than the front end.(4)in the same capacity,the more dispersed the access,the smaller the network loss.(5)it is not better to access pv capacity,which will seriously endanger the quality of power network and the safety of equipment.Therefore,it is of great significance to strengthen the planning of photovoltaic power generation and grid connection,which should not only control the total amount of access,but also optimize the access location,rather than blindly large capacity and network.In addition,in order to prevent the occurrence of isolated island events,the inverter must have anti-island function,and the anti-island device should be added to ensure the quality of power supply and the safety of electricity.