Research On Grid-connected Control Strategy Of Distributed Generator And Its Influence On Distribution Network

With the rapid development of China's power industry,power equipment and factories have rapidly increased.As traditional fossil energy sources are gradually depleted,new clean energy sources are increasingly used.Among them,distributed power sources such as wind power and photovoltaic power generation are favored,especially the grid connection of distributed power sources is particularly important,but after a large number of distributed power sources are connected to the power grid,it has a great impact on the power quality of the distribution network.When the penetration rate of renewable energy continues to increase,the reactive power regulation,voltage and network loss of the distribution network are greatly affected.Therefore,the study of distributed power grid connection control strategy and its access to the distribution network Influence has important theoretical value and practical significance in engineering.The specific research contents are as follows:(1)Study the typical control strategy of the grid-connected inverter of distributed power generation constant voltage source,including two basic control modes: master-slave and peer-topeer.After analysis,it is found that the slave source in the master-slave control is too dependent on the master source,and the peer-to-peer control sacrifices the stability of the frequency and voltage in the microgrid.In this paper,from the perspective of traditional constant voltage source gridconnected inverter control method,Digsilent simulation software is used to verify the smooth switching characteristics between distributed power supply and large power grid.The verification shows that the improved strategy can withstand a single distributed power supply off-grid The influence of switching between the grid and the grid effectively improves the safety and reliability of the distributed power supply.(2)The wind power generation system is one of the important components of distributed power generation.This paper studies the offshore double-fed wind turbine converter system and its transmission system based on the flexible DC transmission technology.At the same time,the mathematical model and control strategy of its converter system are elaborated in detail.The simulation model of the entire system is built and verified using Digsilent simulation software.The results further show that the converter system and its transmission system are feasible and stable.(3)Combined with the characteristics of the random output of distributed power sources,a holistic analysis method is used to calculate the power flow of the radial distribution network.After the distributed power source is connected to the distribution network,due to its different access location and different access capacity The impact of distribution network operation.Using the scenario decision method,the problem of reactive power optimization configuration of distribution networks with distributed power sources is studied,and the optimal decision is made from the perspective of multiple scenarios.(4)For the Distflow power flow equation of radial distribution network,it is convexly relaxed by the second-order cone optimization theory.Finally,taking the network loss as the goal,a mathematical model for reactive power optimization of the distribution network with distributed power sources is established,and an example simulation is carried out through the IEEE 33-node grid system,and the results are analyzed.The results show that the distributed power supply connected to the distribution network can effectively reduce the network loss of the system and has a significant voltage support function.The research results can provide decision-making basis for the optimal configuration of distributed power grid connection and its access to the distribution network,and have guiding significance for the distribution network planning in the context of new energy technology development.