Operation Risk Assessment Of Distribution Network Considering Uncertainty Factors

Operation risk assessment of distribution network is an effective tool to measure the safe operation of the distribution network,and provide a reliable reference for dispatchers,so as to identify potential risk factors existing in the distribution network.However,the research on the operation risk assessment of power distribution network is not enough.In this paper,the operation risk assessment of distribution network considering load demand and distributed power output uncertainty is analyzed and studied.Operation risk assessment model is constructed in accordance with the characteristics of distribution network.The model was analyzed from the two aspects of fault probability and fault severity,risk index for system and user is proposed considering load uncertainty of demand of distribution network operation,and stochastic power flow is applied in solving the risk assessment model of distribution network.The IEEE3 feeder distribution system calculation results show that load demand uncertainty influences the distribution network operation risk from the size of load and load fluctuations.It is necessary to take the effect of demand uncertainty in the evaluation of distribution network operation risk process into account.In order to analyze the influence of distributed power supply uncertainty on the operation risk of distribution network,this paper studies the fault recovery strategy of distribution network with distributed generation.The optimal DG output,the worst DG output and the average DG output of three typical states are presented,and the islanding scheme is determined.Taking the PG&E69 node distribution system as an example,the operation risk of distribution network under three typical conditions is calculated.The results show that under the condition that the DG capacity is small and the power quality factors are not considered,the operation risk of distribution network is negatively correlated with the DG output.Therefore,it can be considered that the operation risk of distribution network in three typical cases is the minimum,maximum and average risk value in the statistical period.Distributed power supply is often accompanied by a large number of power electronic devices,coupled with its intermittent and random nature of the harmonic pollution,voltage distortion and other power quality problems increasingly apparent.In view of this phenomenon,the existing risk indicators are expanded,and the power quality factors are taken into account.The simulation of PG&E69 node distribution system shows that,considering the power quality factors,the distributed power access to distribution network increases the operational risk of the system.Based on the sensitivity analysis,the weak link of the distribution network is mined.The operation risk of distribution network is expressed as the function of line fault probability,load demand and DG output.The sensitivity of distribution network operation risk index is calculated,digging out the line,load node and distributed power supply which have important influence on the operation risk level of distribution network to provide the corresponding reference for the dispatcher.