Dynamic Optimal Dispatch Of Active Distribution Network With Electric Vehicle Aggregators

With the penetration rate of distributed generators improving and the widely use of electric vehicles, power flows in bidirection instead of single directrion in the past distribution networks and distirbution networks has the duty of dispatch beyonds just distributing electric power. Then, active distrbution network is formed. Its objectives are to improve the ability of accepting more renewable energy resource and keep active distribution networks operate safely, steadly and economically and mine more potential benefits of various renewable energy resources for the sociaty. To this end, optimal dispatch of active distribution networks considering electric vehicle aggregators is proposed. Detail works are as follows:Firstly, build models for several usual distributed generators; research impact factors on active electric power fluctuation of interminitent energy resources; take Hainan grid as an example to calculate the active electric power fluctuation of wind, photovoltaic generators with fluctuation range, which shows that it is necessary to balance the fluctuation of renewable energy resource in active distribution networks.Secondly, propose the concept of electric vehicle aggregators to realize that electric vehicles charge/discharge in order and can be dispatched by active distribution networks; build the model of electric vehicle aggregators; propose two methods for electric vehicle aggregators to balance the active electric power fluctuation of interminitent energy resources, that is direct balancing method and controlling union electric power fluctuation index method. Direct balancing method is to keep the value of fluctuation index in a reasonable range by managing electric vehicle aggregators. Controlling union electric power fluctuation index method is to consider intermittent energy resource and electric vehicle aggregators together in economic operation of active distribution networks. What’s more, build the model of real-time pricing demand response from residential users, which considering both of self price elasticity and cross price elasticity.Thirdly, based on the above research works, build the model of bilevel optimal dispatch model of active distribution networks considering electric vehicle aggregator. In the bilevel model, active distribution network day-ahead economic dispatch is on the upper level and electric vehicle aggregator economic dispatch is on the lower level. The main control variables include hourly exchange price and exchange electric power between an active distribution network and electric vehicle aggregators. Hourly exchange price is the leading variable and hourly exchange electric power is the following variable. On the upper level, the objective is to minimize operation cost of an active distribution network and the constraints include electric vehicle aggregator power constraint, exchange price constraint besides normal constraints such as power balance constraint, operation constraints of distributed generators, and so on. On the lower level, the objective is to minimize the operation cost of electric vehicle aggregator and the constraints include energy storage charge/discharge balance constraint, safe operation constraint, the balance of charge/discharge capacity in one day and the union power fluntuation index constraint.Adopt bilevel interation algorithm to resolve the proposed bilevel optimal model: adaptive mutation particle swarm optimal algorithm is used to resolve the upper problem and traditional particle swarm optimal algorithm is used to resolve the lower problem, and then results are interated between the two layers until that resluts satisfy precision requests or the maximum interation times, then the algorithm is end and outputs the optimal results.In the end, take the improved IEEE33 node system to be a test system and design five calculating scenes. The results show that:considering electric vehicle aggregator into optimal dispatch of active distribution network can decrease operation cost, balance the fluctuation of interminitent energy resources and keep the grid operate more safely; it is more reasonable to implement optimal real time pricing scheme on electric vehicle aggregators.