Reliability Evaluation Of Microgrid Considering Energy Storage And Control Strategies

With global energy exhausting and environment protection becoming more severe,exploitation and utilization of renewable resources have been concern of more and morecountries in the world. As a single and controllable unit, a microgrid generally containsdistributed generators, and its flexible power supply mode can improve the utilization ofrenewable resources and customer reliability. Compared to traditional distributionsystems, a microgrid can provide each customer with multi-powers. When an innerfeeder failed, a microgrid can be split into several island regions, among which can besupplied by micro-powers. Power sources of a microgrid directly affects the customerreliability. Compared to traditional resources, renewable resources output have theproperty of randomn and intermittent, which usually leads to complexible microgridoperation and control. Therefore, the microgrid reliability evaluation becomesextremely difficult. In other words, reliability evaluation methods of traditionaldistribution systems can not be used to accurately evaluate the reliability of a microgrid,and then the existing reliability evaluation theories and methods should be will beextended to be suitable for microgrids.This thesis proposes a generation model considering energy storage and controlstrategies for microgrids; Basing on the model, this thesis use sequential Monte-Carlosimulation to evaluate generation system adequacy.First of all, according to outputcharacteristics, it should caculate the output power based on energy conversionfunctions for each micro-power source. Then, it formulates three possible operationstrategies by analyzing reliability of different control strategies. At last, energy storagemodel and power model is built by considering different operation strategies and controlstrategies separatly. Because the models reflects actual operation characteristics, andconsiders the influence of energy storage and control strategies in a microgrid, So, it isno longer the sum of all micro-powers source output. The adequacy of example systemis evaluated by this algorithm, and the economy of different operation strategies, effectof reliability parameters and capacity configurations are analyzed. The result shows that:it has a great impact on reliability for energy storage models under different operationstrategies and microgrid control strategies.Considering the influence of network structure and generation capacity, this thesisestablishes an outage influence matrix of microgrid load points, and put forwards a reliability evaluation algorithm using the sequential Monte-Carlo simulation techniqueby analyzing the outage factors of inner loads in an island microgrid. Throughsimulating the operating states of inner non-power equipments, generation systempower output and load values of each node on every hour, the load points shedding aredetermined based on power balance and load order of priority. At last, load point indicesare counted and system reliability indices are caculated during simulation period. Theexample shows that: the model and algorithm can accurately evaluates the reliabilityunder different control strategies for a microgrid contained energy storage.Taking into account the impact of upper grids, this thesis builds outage influencematrix by equivalent reliability of upper grid and analysis of loads outage factors; thenput forwards the sequential Monte-Carlo simulation algorithm by using the generationmodel of a grid-connected microgrid. Sampling the states of upper equivalent grid andnon-power equipment, determining the operating states that it is island or internal fault,and judging the outage influence scopes according to load orders of priority and outageinfluence matrix; At last, it calculated system reliability indices by counting thereliability indices of load points during simulation period. The example shows that: themodel and algorithm is effective to evaluate the reliability for a grid-connectedmicrogrid, and the influence of three operation strategies under two control strategies、reliability parameters of upper grid and loads are analyzed.