Fault Characteristic Analysis And Protection Scheme Optimization Of Distribution Network With Distributed Generation

In order to deal with the energy shortage and environmental problems,human beings are actively looking for new clean energy while promoting energy conservation and emission reduction.There are a lot of clean energy in nature,such as water energy,light energy and wind energy.The development and utilization of these energy resources will hardly have a great impact on the environment.In recent years,more and more attention has been paid to the development and utilization of clean energy.The development and utilization of new energy has become an important means for many countries including China to solve the increasingly serious energy and environmental problems.At present,a large number of hydropower,wind power and photovoltaic power generation have been built and put into use,they are all integrated into the grid as distributed generation.However,the access of distributed generation has changed the original single radial power supply network structure,and the change of power flow direction has brought many impacts on the safe,stable and efficient operation of power system.Therefore,this paper will study the control strategy of distributed generation,in-depth analysis of the impact of distributed generation access on distribution network current protection,and put forward the protection optimization scheme and fault location optimization scheme suitable for distribution network with distributed generation.In this paper,firstly,the control strategy of distributed generation is studied.Because the inverter distributed generation needs to be connected to the distribution network through the inverter,its output characteristics are affected by the inverter control strategy.Therefore,the mathematical model of grid connected inverter in three-phase static abc coordinate system and rotating dq coordinate system is established to study the reverse transformation of distributed generation under normal operation and fault operation at the same time,the low voltage ride through strategy is considered,and the control strategy of inverter distributed generation is analyzed in depth.Secondly,the influence of distributed generation on distribution network is studied,and the influence of distributed generation on current protection of distribution network is mainly studied.The circuit model of distribution network with distributed generation is established.The influence of distributed generation on current protection of distribution network is analyzed theoretically from the perspective of circuit,including the access of distributed generation with different types,different grid positions and different capacity the influence of distribution network on the original current protection of lines.Through PSCAD / EMTDC simulation software,a 10 k V distribution network with distributed generation is established to verify the influence of theoretical derivation of distributed generation on distribution network current protection.Then,based on the above analysis,a protection optimization scheme of distribution network with distributed generation is designed.According to the analysis of the grid connected control strategy of the inverter distributed generation and the influence of the distributed generation on the current protection of the distribution network,using the local fault information,according to the location of the grid fault is in the upstream line,downstream line and adjacent feeder line of the distributed generation,the relationship between the positive sequence voltage and current at the protection location is derived,and the different fault types and the fault occurrence in the distribution network are distinguished When the distribution power supply is upstream,whether the distributed power supply is installed on the back side of the upstream line current protection,different protection starting criteria are established according to the positive sequence voltage and current relationship.According to the fault types,the relationship between the positive sequence voltage and the positive sequence current flowing through the protection installation location is deduced according to the fault type.Some parameters in the setting formula of the adaptive current protection are adjusted to make the setting calculation more accurate.Finally,a distribution network fault location scheme based on the improved optimization algorithm is established.Through the improvement of the existing artificial intelligence algorithm fault section location algorithm,through genetic algorithm to simulate the growth point of plant growth algorithm genetic operation,effectively improve the simulation of plant growth algorithm due to its own algorithm structure of the number of iterations,low computational efficiency.The simulation results show that the proposed method has the characteristics of accurate fault location,high efficiency and high fault tolerance.