Optimal Planning Of Microgird And Energy Storage System

Huge economic and social benefits can be obtained by power utility andcustomers through deployment of Microgrid (MG) due to its following features:flexible operation mode—able to seamlessly switch between grid-connected andislanding mode, cascaded utilization of energy and capability of deliveringheterogeneous power quality and reliability service to end-users. However, thepopularization and application of MG and energy storage system (ESS) are limitedbecause of the expensive cost of distributed energy resources (DER) and ESSespecially. Therefore, the optimal planning of MG and ESS are of vital importance.The models for optimal planning of MG and ESS have been thoroughly studied in thisthesis, focusing on the deficiency of current researches. The presented models arebased on the cost-benefit analysis of MG and spectrum analysis. The work in thisdissertation is summarized as follows:1) A comprehensive cost assessment model of MG is proposed based oncustomers’ point of view. The detailed cost assessment model and method for MGconsists of cost on power purchase, DER, gas purchase, environmental treatment,power outage, network loss, distribution transformer, and benefit on providingancillary services such as reserve.2) An integrated energy optimal planning model for MG, which is PDMG forshort (planning&design for Microgrid), is demonstrated. First, the quasi steady-statemodel of typical DER and load are presented. Load is modeled as primary electricityonly, traditional electricity only, cooling and thermal load according to the differentenergy forms and reliability demand. Then, the minimization of the comprehensivecost of MG is discussed. The PDMG model is constrained to fufill the cooling,thermal and power energy balance, power grid and DER operational constraints,reliability constraints, et al. Distributed energy resources customer adoption model(DER-CAM) is introduced. Both PDMG and DER-CAM are applied in optimalplanning of a campus MG. Case study results show that PDMG is effective.3) A capacity optimization model and method of an ESS is presented based onspectrum analysis. In order to inhibit the adverse effects of renewable energy sources(RESs) fluctuations on the power grid, a capacity determination method of ESS is presented. The spectrum analysis results of RESs output are obtained through discreteFourier transform (DFT). Based on the spectrum ananlysis results, the minimumpower and energy capapcity of ESS can be determined considering the constraints ofcharge-discharge efficiency, state of charge (SOC) of ESS and the upper fluctuationrate limit of RESs target output. A capacity determination method of an ESS forsmoothing the fluctuations of tie-line power flow in a grid-connected MG with highpenetration of renewable energy sources is presented. The proposed method candetermine the optimal ESS capacity to inhibit the adverse effects of RESs fluctuationson the MG and power grid. Meanwhile, the spectrum analysis of the controllablepower needed by the MG for stabilization of tie-line power flow is introduced andanalyzed. The minimum power and energy capacity of ESS in MG can be determinedbased on the spectrum analysis. The results of case study demonstrate the validity ofthe proposed method.