Study On Balancing Power Fluctuations Of Micro-grid Tie-line Considering Controllable Storage Loads

Micro-grid,which contains distributed renewable energy generation,load and energy storage devices,provides an effective solution for high penetration rate of renewable energy.Because the output of renewable energy generation has characteristics of randomness and intermittence,and its fluctuation will harm the distribution system operation,it is necessary to install special energy storage device for suppressing tie-line power fluctuation between micro-grid and distribution system to reduce the harm to micro-grid.However,the cost of energy storage device is high,so installing special storage device for micro-grid separately will cause the increase of micro-grid operation cost,which is not conducive to the economic operation of micro-grid.There are two kinds of controllable energy storage loads such as electric vehicle and air conditioner in micro-grid system,and they can be regarded as energy storage devices.Electric vehicles(EVs),which use electricity to replace oil and have zero emission characteristics,become an important transportation tool in the process of logistics distribution.Besides of driving function,EVs can realize bidirectional flow of power between EVs and power grid through V2G(Vehicle to Grid)and act as the role of storage device of micro-grid.AC load is a device transforming electrical energy into heat energy,and heat insulation has the characteristic of storage in the good performance of the space,so AC load of heat storage capacity can be regarded as electric storage capacity of AC load.At the same time,air conditioning load is the main component of peak load in summer or winter,so its energy storage potential is huge.As a result,this paper considers energy storage characteristic of two kinds of loads to stabilize the micro-grid tie-line power fluctuation.It can avoid installing special energy storage device for micro-grid and reduce the cost of micro-grid operation.Firstly,this paper researches electrical vehicle in logistics distribution system.EVs transport and deliver goods from the distribution center to the customers' node and stabilize micro-grid tie-line power oscillations at the time of reasonable arrangements for EVs routing and discharging strategy.Model proposed by this paper has the goal of minimizing micro-grid operation cost,which contains tie-line power purchase cost,tie-line power imbalance settlement costs,EVs fast charging cost and vehicle loss cost etc.to realize collaborative optimization of EVs route,departure time,fast charging,long and return distribution center of the slow charge/discharge power strategy,and derive the optimal bid tie-line power.The simulation results demonstrate the effectiveness of proposed model.Secondly,this paper considers the energy storage characteristic of AC load,and establishes the micro-grid system with AC load.Under the condition of meeting users' thermal comfort,through arranging each start and stop of AC reasonably,the huge number of total power of AC load is changed and the output fluctuation of renewable energy power generation in micro-grid becomes balance.This model is based on the target of minimum cost of tie-line power purchase cost,tie-line power unbalance cost and AC system encouragement cost to realize the optimal scheduling of AC load in the micro-grid.The simulation results demonstrate the effectiveness of proposed model.Based on standard imperialist competitive algorithm(ICA),this paper proposes the self-adaptively imperialist competitive algorithm(SaICA).By using SaICA,ICA and partheno-genetic algorithm to solve this model,and the result proves the superiority of SaICA.The effects of model optimization result with different distribution period and different degree of micro-grid tie-line power fluctuation are analyzed.Result shows that distribution in the period of great micro-grid tie-line power fluctuation will increase the cost of unbalanced settlement.With the increase of tie-line power fluctuation,the model proposed in this paper has a better effect in balancing the wind power output fluctuation,while with the decrease of tie-line power fluctuation,this model has a worse effect in balancing the wind power output fluctuation.