Power Supply Capability Evaluation Of Active Distribution Network Considering Differentiated Reliability And Post-fault Load Response

The distribution network is the link between the power user and generation,transmission system.Analysing the power supply capability(PSC)of the distribution network scientifically is the key segment to evaluate and plan the city grid detailedly.The traditional evaluation method of PSC needs the distribution network to satisfy the N-1 criterion rigidly during peak load time.Considering the load timing characteristics and peak-valley difference,the peak load duration is very short.And this method can bring excess margin.Therefore,we need to consider the reliability index as a flexible restrain to release the power supply potential.And the different users have different requirement of reliability,the expression of reliability index needs to be different.Meanwhile,the access of distributed generation(DG),energy storage and responsive load will be the main form of distribution network in the future.The impact of DG and demand response in active distribution network(ADN)should also be considered when evaluating reliability and PSC.For this reason,this thesis proposed a PSC evaluation method considering differentiated reliability and post-fault load response of ADN.And it can reflect the balance between changing load value and constant power capacity to improve the efficiency of asset utilization.The specific solutions are as follows:First,in view of the basic elements of photovoltaic,energy storage and load in ADN,a time series output model considering the prediction error and a state model considering the diversity of faults are established.At the same time,a post-fault interruptible load model reflecting the actual users differentiated response capability is established.Then,based on the component model,an algorithm for reliability evaluation of ADN considering post-fault load response is proposed.Combined with the access of DG and interconnection switch,the feeder partition and coding mode of traditional distribution network are improved.And considering three kinds of flexible resources including distributed photovoltaic,energy storage and interruptible load,a joint regulation strategy after fault is established to improve the reliability index.On this basis,a reliability evaluation process based on pseudo sequential Monte Carlo simulation is proposed.Next,a PSC evaluation model for ADN is established,which takes the maximization of PSC as the objective function and the differentiated reliability index or load response cost as the main constraints.A model solving method based on genetic algorithm is also adopted.The model takes the feeder load distribution as the optimization object and can obtain the maximum power supply capability of the network under certain constraints.Finally,the ADN with main transformers is taken as an example and the results show that replacing the traditional N-1 rigid constraint with flexible reliability index can significantly tap the power supply potential of the system.And the effect of PSC enhancement is related to DG capacity or load response cost constraint.Under the condition of differentiated reliability constraints,local optimization of PSC can be realized by combining different reliability requirements of different feeders.The results of the example show that the proposed method can effectively tap the power supply potential of the ADN and has important guiding significance for the planning and operation of the future power grid.