The Risk Assessment Of Voltage Beyond Limits In Active Distribution Network

The large scale of distributed generators(DG) injecting in the grid increased the uncertainties of the power system, made the power flow of the network showing the new features. As the base of operation and risk management, it is important for us to control the voltage level of distribution network in the new situation. Probabilistic load flow, which could take into account of the uncertainties, was concided as an effective method to analysis the working state of the system.It played a key role in the status assessment of the active distribution network.In this paper, based on the research of the probabilistic load flow theory, it provided a new algorithm of probabilistic load flow-cumulant inverse function method, which combined the advantages of both the Analytical method and Monte Carlo simulation(MC). The algorithm was founded on the basis of the node’s linearized power flow equation, using MC to calculate the probabilistic convolution, overcome the truncation error of the moment estimation and the cumulant method. it could get more accurate node status informations.To deal with branch outage, it provided a compensation method combined the branch load flow sensitivity analysis to simulate the fault. At the condition of assuming no branch outage, using equivalent load injection’s 0-1 distribution to simulate the fault, to analysis and assess the system’s states under the conditions of branch outage.In the basis of the probabilistic load flow calculation, combined with the risk theory, it proposed a specific indicator of node’s voltage beyond limits. Using probabilistic index and serious index as the scale, it presented a risk calculation program to esstamate the risk of voltage beyond limits, laid the foundation of risk warning processing and on-line risk assessment.