Smart development of community energy storage in power grid with PV units

Abstract

Energy storage (ES) system has become an inevitable element in smart distribution network (DN) due to massive deployment of renewable energy resources (RERs). ES is capable of solving a number of operational problems in distribution network due to intermittent characteristic of the RERs while providing numerous other benefits such as ancillary services, peak reduction, reliability improvement etc. Among various type of RERs, community level distributed photovoltaic (PV) is the fastest-growing power generation system due to its technological advancement; declining price and better fit into consumer area. Thus, impact of intermittent PV output power is more severe in community level where the consumption is happening. Hence, the idea of bringing ES close to the source of the problem has led to the development of concept called community energy storage (CES).Most available studies claimed that the deployment of CES is more effective in alleviating the impact of high PV penetration while offering more benefits than the centrally located substation storage if properly planned and effectively controlled. However, comprehensive review found that very scant analytical evidences were shown to prove the statement. Besides, currently CES allocation is determined based on maximizing specific benefit while neglecting others benefits of its deployment. Very scarce previous works provided a complete allocation framework that can optimally site, size and dispatching CES units by considering both its technical and economic benefits. Hence, this thesis aims to develop comprehensive CES planning strategies in residential distribution network with rooftop PV by considering various technical and economic issues.The first contribution of the thesis is the assessment on the impact of ES load levelling on the energy loss reduction in DN with PV units. In addition, a methodology based on the loss sensitivity factor (LSF) is developed to identify the proper location of ES for minimizing energy loss in DN. Secondly, an analytical allocation framework that can determine the strategic location, size and operational characteristic of CES unit for load factor enhancement, energy losses reduction and voltage profile improvement is proposed in the thesis. Within the proposed planning framework, a new probabilistic method is developed to model the uncertainty of PV generation in an existing residential system. This model is simple and requires less input data and calculation than the existing probabilistic PV model. Thirdly, the thesis presents a comprehensive planning framework for single and multiple CES units based on Cost Benefit Analysis for maximizing the NPV of CES deployment. The planning strategy accommodated all possible benefits and costs incurred from the deployment of CES. Sensitivity analysis on the impacts of the number of CES units, CES’s price reduction, PV penetration and load models on the profitability of CES deployment are also included. Finally, the thesis proposes a novel framework of virtual microgrid (VM) construction with CES in residential network with rooftop PV for maximizing the NPV of CES investment. In the proposed framework, a new method for designing VM and a novel business model for CES are introduced to increase the profit gained by the utility and consumer.The studies reveal that all the proposed allocation strategies are able to achieve their objectives of CES deployment which consists of various technical and economic benefits. In addition, a maximum profit can be gained by clustering the residential network with rooftop PV into a specified number of VM and optimally allocating CES unit in the VM using the presented framework. Moreover, it is revealed that there was an optimal number of CES units and VM that should be deployed for achieving maximum NPV. Hence, inclusion of all possible financial benefits and costs of CES in the planning strategy may enhance CES prospect in ADN and provide comprehensive guideline for the utility in deploying CES. Furthermore, it is shown that by renting out some of CES energy to the prosumer in residential network, increment on the profit gained by CES investor and reduction on the consumer’s electricity bills could be achieved.