Energy Management Optimization And Battery Economical Evaluation Of Digital-analog Hybrid Active Distribution Network

With the lack of traditional energy,renewable energy(RnE)in micro-grid is developing fast because it's flexible,scattered,small-scaled,closer to the user and clean.Energy storage system(ESS)can not only reduce the fluctuation of RnE to improve power quality,but also realize the function of peak load shifting,improve the performance of network,and reduce the cost of power purchasing through timely absorption and release of the power.It's essential to choose the battery reasonably and get proper charging-discharging strategy in order to improve the operation efficiency and reduce the operation cost of the micro-grid.This dissertation introduces an energy management optimization strategy of micro-grid using model predictive control(MPC)based on the electrical distribution network of Beijing Jiaotong University,and then build a digital-analog hybrid platform with a virtual storage system composed of battery models to choose the battery and get proper charging-discharging strategy in order to minimize the operation cost of the micro-grid.The main contents of the studies are as follows:(1)In this dissertation,we study and establish the equivalent circuit model of lithium ion battery and lead-acid battery,evaluate the damping of battery performance with equivalent cycles.Then verify the accuracy of the dynamic characteristics and the damping performance of the model through simulation.Considering the real-time attenuation of the battery,a cost function of ESS is proposed for the economical evaluation.(2)An energy management optimization strategy based on MPC and is introduced,with the accounting mode of maximal capacity and the optimization goal of minimizing the operation cost.This strategy considers some constraints of load,RnE,ESS,etc.And is formulated in mixed-integer-linear-programming(MILP)scheme to get optimal solution.Then controls the power of load,RnE,ESS to improve the efficiency of the system and reduce the operation cost of micro-grid.(3)A digital-analog hybrid platform of active distribution network is built using the software of Matlab/Simulink and Labview.The platform is integrated of several modules,such as virtual storage system,energy management optimization strategy calculation module,meteorological data acquisition module,distribution network power data acquisition and monitoring module,etc.This platform is used for energy management optimization strategy verifying and economy evaluation of ESS.(4)Then simulate on the strategy,we analyze the output of the strategy and the cost of ESS using the methods mentioned above.Results show that the optimization algorithm can get real-time charging-discharging strategy and effectively reduce the operation cost through calculation every 15 minutes with the input of load demand,power of RnE,real-time electricity price and the residual capacity of ESS.(5)The best "battery type-optimization mode" is obtained through analysis.Results show that lead-acid battery has better economy than lithium in battery in micro-grid energy storage area.The main innovation of this thesis is to build the digital-analog hybrid platform of the distribution network.We can get different combination of "energy management strategy—energy storage battery" according to different simulation scenarios to get the best one,and we can greatly reduce the cost of the actual test based on the platform.