Fast Algorithm For Distribution System Reliability Evaluation Considering Power Flow Calculation

With rapid development of social economy, the requirements on power quality become higher and higher.As the last layer of the power system, study on the reliability of distribution network is getting attention gradually. Taking the element as a clue, the reliability evaluation of distribution network is explored.The first chapter introduces two main methods of distribution network reliability evaluation, namely analytical method and simulation method. The former mainly introduces the failure mode and effect analysis method, the minimum path method, the network equivalent method, the minimum cut set method and the Bias network method and so on. The latter mainly introduces the sequential simulation method and the non-sequential simulation method. In this chapter, we also describe the classification of reliability index system according to different classification criteria. This paper mainly introduces the reliability index system to the evaluation object as the classification standard.In the second chapter, the paper establishes the reliability model of component based on the two parameter Weibull distribution, and uses the maximum likelihood estimation method to calculate the shape parameters and scale parameters of the model.The hot spot temperature model is applied in the transformer model, considering the temperature of the transformer and environment, as well as the temperature between the various parts of the transformer. The temperature transient model in applied in the cable model, and the temperature changes of the cable itself and the surrounding medium are analyzed.In the third chapter, reliability evaluation for distribution network is divided to upstream and downstream delivering process, according to effects of the components during the process and the reliability indices in the second chapter. The upstream delivering process indicates the effects of the faults on the downstream area to the upstream area, and vice versa.The main network, composed of the main power and backup power supply, is applicable to the distribution network with multiple alternative power supplies. The branch network, composed of the network except the main part, also suits the complex structure of the distribution network for long feeders.The fourth chapter proposed a protection component model and simplifies the transmission path based on the effect and position of protective component during the delivering process in the third path. The common model of distribution network component is defined, and the upstream and downstream delivering characteristics are improved, and the computation is effectively reduced. According to the relationship between the protective component and the reliability indices, the reliability indices are furtherdivided to the achievement of delivery of the full distribution network.In the fifth chapter, the set of protection elements and the corresponding action vectors are defined, for the protecting mechanism of the fault and the fast evaluation of distribution network in the fourth chapter. According to the constraints of power flow, and the set of objective function, the paper finds the optimal fault isolation and recovery model. With the consideration of the mode and the sectionalizing switch operation, the delivering process of the reliability indices further improves the upstream and downstream delivering characteristics.