Research On Risk Assessment In Distribution Network With Distributed Generations

A lot of distributed generations are access to the distribution system,which changes the operation and structure of the system.Its randomness and discontinuity of output power will likely have a negative impact on the power grid,and may introduce risks to safe operation of the distribution network.The distribution network is directly connected to the consumers,so it affects the security and reliability of power system.It is not only of theoretical value but also of practical significance to evaluate the risk of distribution network with distributed power supply,find the potential danger of system operation and improve the reliability of power distribution system.Based on the semi-invariant stochastic power flow calculation,this paper studies the influence of different types of distributed power supply on the distribution network risk under different capacity and access position.The main work is as follows.A complete risk assessment model is established for distribution network with distributed power supply.First,stochastic models of the system components are established,which includes the probability model of wind power generator,photovoltaic output power and load.Then,the risk index of distribution network with distributed power supply is established.The probability and the severity index are calculated from the two points of the node voltage overrun and the branch flow.Considering the stochastic characteristics of distributed power output and load power,a semi-invariant stochastic power flow algorithm is used.By using the linear power flow equation and using knowledge of probability statistics and series expansion method,the probability distribution of the each node voltage and each branch power is obtained.The influence of distributed power supply on the distribution network risk at different access nodes and different capacity accesses is studied.In the two cases that wind power generator or PV is connected to power distribution system alone,stochastic power flow algorithm is used to quantitatively calculate the node voltage over-limit risk index and the risk index of branch power flow under different conditions,which is reasonable for distributed power supply network and provides important theoretical value and practical significance.Risk control of distribution network with distributed power supply is carried out according to the possible risks of distribution network.The mathematical model of risk control is established.The objective function is to make the sum risk index of all nodes and branches the minimum.The particle swarm optimization(PSO)algorithm is adopted to plan the location and capacity allocation of the wind generator and PV into the distribution network,so as to reduce the risk of the distribution network operation.