Research On Grid-connected Photovoltaic Power Performance Evaluation Based On Measured Data

With the ever-increasing world energy demand,the depletion of fossil fuels,the global energy structure is changing,and the renewable energy power industry has rapidly emerged.However,the access of new energy sources has changed the structure and trend of the power grid,and will inevitably bring about problems such as power quality,operation planning,and relay protection.Aiming at the problems of current grid-connected performance detection devices for new energy sources in China that have a single function,poor accuracy,low real-time performance,and long-term lack of comprehensive system-effective evaluation methods,the thesis takes a 20MW photovoltaic power station in Shenmu County as the research object to develop a testing program and evaluation system.Based on the measured data,the characteristics of grid-connected operation are studied,as the examples are provided for the performance evaluation of other new energy sources.The main contents are as follows:The development trend of photovoltaic power generation technology at home and abroad was investigated.And according to the grid power quality data analysis algorithm,the testing device of the grid performance,and the evaluation method and measures of the photovoltaic system grid-connected performance,the current research status and existing problems of the grid-connected photovoltaic power supply are described.Taking the two-stage grid-connected photovoltaic system as the research object,the key technologies of power quality control are deeply analyzed,Comparing to various maximum power point tracking algorithms,inverter topology,control strategies and vector modulation methods,an optimal selection basis is proposed to improve grid-connected power quality.By building a photovoltaic array and a disturbance simulation model based on Boost circuit,the output characteristics of photovoltaic cells are analyzed,and the feasibility of the selected maximum power point tracking algorithm is verified.A double closed-loop decoupled direct current control strategy based on SVPWM control is proposed to realize the dynamic reactive current compensation of the inverter,and a photovoltaic system simulation model is established for verification.The simulation results can realize unity power factor grid connection.By summarizing domestic and international PV grid-connected standards,the required limits for grid-connected indicators have been obtained.Aiming at the problem that the existing power quality analyzer has a single function,poor accuracy and insufficient real-time performance,the calculation methods of different power quality indicators are studied.The power quality data analysis software based on the FFT algorithm framework is designed to realize the real-time calculation of power quality indicators such as system frequency,voltage deviation,harmonics,and three-phase unbalance.Taking the PV power plant as a practical example,a detailed test scheme was formulated to carry out various field tests,and a power quality analysis method based on the division of the output power of the photovoltaic power plant was proposed to solve power quality problems in different power ranges.Data analysis software was used to evaluate the performance of photovoltaic power supplies from the aspects of power quality,active power control,power rate of change,and reactive power adjustment.Therefore,the feasibility of the program and the practicality of the data analysis software were verified.