Research On The Influence Of Grid-connected Photovoltaic Power Generation On Power Quality Of Distribution Network

With the proposal of China’s carbon neutral carbon peak target,it also means that the investment in renewable energy of wind power,solar energy,hydropower and other renewable energy will be further increased in the energy supply side.Make China’s power supply system presents a diversified development trend.Photovoltaic grid connection will once again become a hot topic of research,because photovoltaic grid connection can effectively alleviate the consumption of traditional energy.The structure of the distribution power grid changes caused by the access of the photovoltaic power generation system.If the power grid is in abnormal operation for a long time,the safety of electricity equipment,power grid and power supply will not be guaranteed.If measures are not taken,the voltage index of the original distribution network,current harmonic content,grid frequency will be affected,such as the maximum power tracking control method will affect the network voltage,current and power fluctuations and current harmonic distortion,island effect power distribution of distribution network,including the DC component,three-phase imbalance will change the distribution network quality.Therefore,it is necessary to analyze the impact of electric power quality after photovoltaic grid connection,not only to ensure the safe operation of the power grid and electricity equipment,but also to ensure the growing electricity demand for users.This paper focuses on the influence mechanism of photovoltaic grid-connected power generation on the power quality of the distribution network,and establishes a model to verify the scheme with minimal impact.Firstly,this paper studies the equivalent model and output characteristics based on the working principle,analyzes the parameter design of PV inverter,LC filter and inverter power control strategy,and establishes a single-stage three-phase PV gridconnected system on PSCAD platform to verify the correctness of the power control strategy.This paper presents a maximum power tracking algorithm based on the improved particle group algorithm,and optimizes the distribution network power quality by comparing the variable-step conductance increment method and the fuzzy control method.This paper establishes the anti-island effect detection model to explain the island effect principle and the island effect hazards.The model of grid operation to the island is established,and the rationality of the main controller and slave controller control policy is verified by observing the changes of power,voltage,current and frequency during the switching process.Secondly,the paper analyzes the causes of the DC component and the countermeasures to suppress the DC component.In this paper,the photovoltaic grid connection model is established under three-phase imbalance to observe the inverter output current waveform and the harmonic distortion rate,and found that the inverter side of the photovoltaic power generation system will output three harmonic components and inject them into the distribution grid.Finally,this paper analyzes the effect of photovoltaic grid connection on network loss and voltage of distribution network,and establishes a 33-node model in PSCAD platform.Multiple experiments were simulated to conduct photovoltaic power generation system grid connection at different capacity and different positions,and to analyze the change characteristics of system voltage and network loss.In addition,DG cost and active loss are proposed as the index to optimize the installation number,capacity and location of DG based on the genetic algorithm to realize the optimal configuration of the photovoltaic power generation system under the minimum influence of the photovoltaic power grid connection on the power quality of the distribution network.