Effect Of Large-scale PV Power Station On Grid Stability And Comprehensive Evaluation On Operation Safety Of PV Power Station

With the rapid development of economy and society,coal,oil,natural gas and other fossil energy are gradually reducing and the environment problems are becoming prominent,the exploitation of clean energy like photovoltaic is become a consensus of the energy strategies among the countries in the world.However,the large-scale centralized exploitation and production of photovoltaic projects in short time as well as lacking of operating management experience led to frequent power network accidents,photovoltaic development and power grid development are seriously unbalanced which not only cause great potential security risks,but also constraints the healthy development of photovoltaic power.Therefore,this paper studies the effect of large-scale photovoltaic power station access on grid stability and makes a comprehensive evaluation on the operation safety of photovoltaic power station.Firstly,this paper introduces the model of PV system and DC system,gives the state equations of PV inverters in the three types of L,LC,and LCL under ?? and dq coordinate axis.Subsequently,this chapter expounds the overall structure and control method of DA direct current system model in PSD transient stability programSecondly,this paper studies the effect of large-scale photovoltaic power station access on grid stability.Based on the simulation analysis model built by PSD-BPA software,the paper compares the differences of simulation curve in the aspects of voltage,active power and reactive power in the condition of cutting three-phase short circuit roadblock of photovoltaic power station in different volumes,and studies the external characteristics of large-scale photovoltaic power station which have faults.Subsequently,this paper analyses the stability influence of access systems' power angle after large interference based on different photovoltaic access ratio and provides relating conclusions.Lastly,based on the reactive power and voltage characteristics of the DC system,this paper studies the characteristics of the photovoltaic DC transmission by means of simulation modeling,and gives the final conclusion.Finally,this paper establishes operational safety evaluation system of large-scale PV power stations with five indexes including the success rate of low voltage ride-through,the ability of active wave suppression,the over-voltage limit of grid point,the dynamic reactive power response capability and the success rate of frequency cross-over,and realizes quantitative calculation of indexes.Based on this,entropy weight method and AHP method are applied to the weight calculation of operation index in large-scale PV power stations.By means of the index's subjective and objective weights determined by entropy weight method and AHP method,and then calculate the comprehensive weight of photovoltaic power station operation index by “Multiplication” integrative methods and finally sequences the comprehensive evaluation of photovoltaic power stations' operation performance by means of gray relative analysis method.In the end,through the analysis of relevant examples,it is proved that the comprehensive evaluation method of large-scale PV power station proposed in this paper is practical and effective.