Research On Optimal Scheduling And Storage System Degradation Cost Model Of Virtual Power Plant

As an emerging management form of distributed energy, virtual power plant (VPP) has experienced booming development worldwide during recent years. Battery energy storage system (BESS) is one of most important components of VPP, and it can help improve system stability and economical performance. However, due to its inherent physical and chemical characteristics, there exists evitable degradation cost when BESS participates in optimal scheduling of VPP. This has severely decreased the economic benefit of VPP and influenced it's optimal scheduling decisions. Therefore, it is worth to study the effect of BESS degradation cost on the profit gained in the electricity market. This will offer more reasonable scheduling decisions for VPP agent and enhance the competitiveness of VPP when trading in electricity market. Using this as a starting point, the following research works have been done in this paper for optimal scheduling and storage system degradation cost model of VPP:First, this paper introduces the concept of VPP and proposes an optimal scheduling method of VPP considering uncertainty of the electricity price and intermittent generation of renewable energy resources. Combining existing mechanism of electricity market, this paper analyzes the main forms of VPP for trading in the electricity market. The sovling methods of two-stage stochastic programming are studied and its superiority index and range of application are summarized. The conditional value at risk (CVaR) is introduced to evaluate the market trading risk caused by the aforementioned uncertainties.Then, the optimal scheduling model of VPP without the consideration of battery degradation cost is proposed. Gas turbine generator and BESS are scheduling objects of this model and the randomness of generation of wind power and photovoltaic (PV) generations are also considered. The scheduling objective is maximize the expected profit of VPP on condition that the power output limits of Gas turbine generator, security operation constraints of VPP and stable operation constraints of BESS are statisfied. The results of simulation show that, compared with the deteminstic approach, this stochastic scheduling method can effectively solve the uncertain problem with renewable energy resources and electricity price and improve economic performace of VPP when trading in electricity market.Finally, the optimal scheduling model of VPP consideing battery degradation cost is proposed to solve the effect of not considering battery degradation cost on its lifetime and optimal scheduling decisions of VPP. The effect of depth of discharge (DoD) and ambient temperature on battery degradation cost is studied. A novel battery degradation cost model based on cycle counting method and a more comprehensive battery degradation cost model based on weighted kWh-throughput method are proposed. The battery degradation cost is incorporated into the objective function and the short-term and mid-term optimal scheduling decisions of VPP for market trading are obtained. The simulation is done in a VPP containing a gas turbine generator, a wind power plant, a PV power plant and a BESS. The results show that this model can effectively prolong the lifetime of BESS and improve the economical performance of VPP.This paper proposes an optimal scheduling model of VPP considering battery degradation cost to for the degradation problem of BESS during scheduling process. The study of this paper can provide some guides for optimal scheduling of VPP when it is massively applied worldwide.