Research On Island Searching And Energy Storage Allocation In Distribution Network With Distributed Generation

When there is fault in power system,some part of distribution network will operate in islanding mode.If there are distributed generation in island,this area may support some or the whole load under proper condition.This action will reduce the loss of power failure.But since the stochastic power output of solar and wind,when system operates in islanding mode,the distributed generation may have been in a variety of power output levels and may have failed to guarantee the power support capability for all load in island.This problem could be improved or even solved by the allocation of energy storage systems.But it remained to be clear on how to allocate energy storage system in a proper way which could fully consider the feature of distribution network structure and distributed generation.The relevant topic was important to be fully understood.For the problems above,this thesis focused on the following subjects:(1)This thesis evaluated the importance degree of load by using the concept of load value,took the maximum sum of load value in island as objective and modeled the island path searching problem(Also called island searching strategy).Since the stochastic power output of distributed generation,we should took all possible power output level into consideration.Based on the traditional method,this thesis proposed the improved island searching strategy,which improved the searching outcome with higher load value,with no bother from multiple power source output power levels.The proposed searching strategy determined the power source output level according to load level,got the sets of all best power path in island which would benefit in power supply priority for important load.(2)This thesis took the maximum load value supported by energy storage per unit as goal,made use of the outcome of the sets of all best power paths to guarantee the power supply priority for important load,made use of distributed generation power output curve to determine the probability distribution function of load value supported by energy storage system and finally decided the optimal energy storage capacity which will have the maximum load value supported by energy storage per unit.The proposed index could both consider the load support capability and cost of energy storage.In the end,the simulation case verified that the proposed island searching strategy could find the best power path which would maximum the load value and the proposed energy storage optimal capacity allocation method could effectively have the results.