Optimization And Design Of Hybrid Energy Storage System With Dispatchable Wind/Photovoltaic Power Output

As the most attractive green resources, wind power and photovoltaic power gain worldwide popularity in the last few years. To alleviate the impact of renewable energy that accesses the grids, especially on the stability, dispatchability and security, people have proposed a range of new methods and schemes. Among all the solutions, the energy storage system, or ESS, is one the most promising approaches that scholars are talking over. Traditionally, pumped-hydro energy storage is the top one choice in terms of large-scale energy storage; it has stepped into the stage of successful commercialization. However, its application is severely limited as a result of inherent geography constraints; it is available on small parts of the land.Today, many novel storage systems emerge in large numbers, consisting of electrochemical energy storage technologies, such as the lithium ion battery, the all-vanadium redox flow battery, the sodium-sulfur cell and the supercapacitors. The burgeoning energy storage systems are increasingly promoting the development of smart grids and advanced energy storage technology; the latter one, to some extent, turns into the new research field of the power grids in recent years. Electrochemical battery is always chosen as the long-time energy storage technology for its high energy density. With higher capacity density and lower energy density, supercapacitors are generally utilized as short-time energy storage scheme. Thus, considering advantages and disadvantages of energy storage systems, single-medium energy storage system has no longer meets the demand of various practical projects. Accordingly, the concept of hybrid energy storage system, or HESS, is come up by expert advisors in the power sector. Among current demonstration projects in China, hybrid energy storage systems have shifted from special arrangements into the mainstream. Hence, the research on the cost, performance, optimization and design of energy storage technology is of great importance.The thesis first investigates domestic demonstration projects, analyzes their medium and energy capacities, and observes the principal components. Then, a range of energy storage technologies on the HESS field are discussed to figure out their merits and demerits. The paper gets down to analyze the considerations of the HESS cost, and discusses the chemical properties in different medium, deeming the ramp rate as the first determinant that must be observed in the cost calculation. After that, Copula functions are introduced for the purpose of unscrambling the dependence between the power of wind and PV plants, which is perceived as the second indispensable factor. Then, the paper presents the control algorithm of buffered power and cost calculation formula, with the energy capacities of the BESS and SCESS simultaneously determined by integration. By this means, the relations between the cost of HESS and these two discriminants, including the dependences and the optimal ramp-rates, are explored in all sections. All above innovative research work makes the promotion of HESS in China become more feasible.The paper comes to a conclusion that the cost of hybrid energy storage system is not only relevant to the performance of ESS medium, but also relies upon the dependences between the wind and PV power, the on-site landform, topography and climate. The program designed in the last chapter successfully evaluates the cost and energy volume ratio of the HESS, and resolves the problem about capacity optimization and cost budgeting in the practical application.