Study On Energy Storage Sizing Method In Networked Microgrids

In recent years,frequent occurrences of extreme natural disasters result in large-scale power outages and huge economic losses all over the world.Consequently,the resilience to deal with the extreme events in the distribution network has received extensive attention in the industry and academia.Microgrids(MGs)close to each other in geographical locations can be interconnected to form networked microgrids(NMGs).Coordinating the energy interaction between MGs,the load restoration capabilities can be improved when extreme events occur.Energy storage systems(ESSs)play significant roles in the MGs.Also,the energy storage sizing will have great effects on the operation economics and self-healing abilities of the NMGs.In this paper,based on different planning horizons,a bi-level energy storage sizing model in NMGs is proposed for profits maximization.Not only the close relationship between the MG planning and operation is considered,but also the reliability and resilience indices in constraints are included.Considering risks resulted from the fluctuations of photovoltaic(PV)generation and load consumption,the multi-period energy storage expansion schemes are proposed under different risk strategies.The work of this paper includes the following aspects:(1)In the NMGs composed of non-dispatchable distributed generators(NDDGs)based on renewable resources,dispatchable distributed generators(DDGs),critical/non-critical loads,the operation scenarios are divided into normal operation,typical fault and extreme fault scenarios according to whether outages occur,the differences of the fault locations,severities and durations in the distribution system.The energy interaction in the NMGs under three types of scenarios is introduced in detail.(2)Considering the interrelationship between planning and operation in the NMGs,a bi-level short-term energy storage sizing model is proposed.With reliability and resilience indices in constraints,the upper-level model is focused on the optimal ESS sizing problem in each MG,aiming at maximizing annual net profit.Considering the energy exchange under three types of scenarios in NMGs,the lower-level model is aimed at operation profit maximization and the operation strategies under multiple operating scenarios are investigated.The optimization results when MGs operated under independent or networked modes are compared.(3)Considering the risks originated from the uncertain parameters in NMGs,the growth of load demand and capacities of micro-sources,as well as the upgrade deferral profit of ESSs,the multi-period bi-level energy storage sizing models are proposed based on the risk neutral and risk averse strategies,respectively.The expansion schemes of ESSs as well as the operation strategies under multiple types of scenarios in each year are optimized.The optimization results considering different operation scenarios and risk strategies are compared from economics,load restoration capabilities and investment risks.