The high proportion of renewable energy grid integration imposes greater demands on the adequacy of various regulatory capacities, including peak shaving, frequency regulation, ramping, and reserve capacity. Currently, China has initiated capacity compensation mechanisms based on capacity pricing but has yet to establish a capacity market. Market mechanism designs—including compensation calculations, cost allocation, and balancing responsibility assignment—remain constrained by the absence of assessment methods for evaluating the flexible regulation contributions of different types of entities. Therefore, there is an urgent need to develop a differentiated assessment method for effective capacity across multiple entities. This approach will provide theoretical support for advancing China's capacity pricing compensation mechanisms, capacity market development, and the design of market systems for reserve, ramping, and ancillary services.
The proposed multi-type entities effective capacity assessment methodology integrates historical forecast and actual output data of the subject units, operational and regulation performance parameters, along with historical system load data and inter-provincial interconnection data. It differentiates the assessment of system power, frequency regulation, ramping capability, and reserve capacity performance for various unit types from the perspectives of power contribution during critical periods and flexible regulation capability. The fuzzy TOPSIS method resolves uncertainties and ambiguities in unit reliability levels, reasonably reflecting different unit types' ability to ensure long-term system capacity adequacy and respond to short-term regulation demands. Furthermore, this study quantifies the system's demand for different capacity types and their value by calculating multi-type capacity supply-demand coefficients and system capacity shortfall risk indicators. Based on this, the effective capacity correlation coefficients for diverse units under multi-type capacity demands are computed using a unified evaluation model and process.
The paper designs quantitative indicators for unit reliability levels by considering power contributions during critical periods and flexible regulation capabilities. It proposes system capacity value assessment indicators that incorporate multi-type capacity supply-demand coefficients and capacity shortfall risks to determine the actual contribution capacity of different unit types toward supporting system capacity adequacy and flexibility. Through case study analysis, this paper quantitatively calculates the reliability assessments and system capacity values of different units, thereby enabling differentiated evaluations of the effective capacity of various unit types. The case study validates that the proposed effective capacity evaluation method can assess differentiated effective capacities for various entities, including renewable energy sources, under different seasonal conditions. Simultaneously, the case study conducts a differentiated dynamic assessment of changes in the effective capacity coefficients of various entities under different capacity supply-demand scenarios, further demonstrating the applicability of the proposed multi-entity effective capacity evaluation method to changes in system capacity supply-demand conditions.
This multi-type entities effective capacity evaluation method balances agent reliability levels and system capacity value, providing a rational approach to quantify the differentiated contributions of various agents to power system capacity adequacy. It lays a theoretical foundation for China to explore establishing reliable capacity assessment mechanisms for diverse agents and developing capacity compensation mechanisms tailored to different agent types.
EFC方法用于评估高随机性新能源和储能的可靠容量贡献。EFC于2024年7月由国家电网电力系统运营商(electricity system operator, ESO)提出,旨在量化此类待测资源在保持系统可靠性时可以替代的固有常规发电容量[29]。EFC评估方法可有效确保容量市场的公平性和效率,通过按比例分配储能等灵活性资源在特定可靠性标准下(如3 h损失负荷期望)的总可靠容量贡献。
随着新型电力系统新能源接入比例的提高,电力系统稳定运行所需满足的电量、调频、爬坡与备用容量需求的重要性发生了改变。系统的容量需求逐渐从以电量支撑为主转向灵活调节,这使得调频、爬坡和备用容量的需求变得更为迫切和关键。因此,本文采用边际预期未供电能量(marginal expected energy not supplied,MEENS)来量化系统缺失不同类型容量所造成的风险。边际预期未供电能量指的是多元主体提供不同类型容量增量变化对预期未供电能量的边际减少量,可以用于评估系统对于不同类型容量需求的关键程度。为了计算边际预期未供电能量,可以使用MCS等场景模拟法,通过运行多场景评估,求解多个模拟场景下的基准和待测预期未供电能量平均值。具体计算方式如下。
由于同一类型主体在省级/区域电网内不同分区与个体间的可靠性水平可能存在差异,例如,省级电网内不同分区或地理区域的风光条件各不相同,导致新能源平均出力、波动水平在不同地域之间存在显著差异,这可能导致某类新能源的分时段同时率和波动率指标计算结果呈现区间分布特征。此外,主体的规模、成本和技术水平在一定时期内也会发生变化,影响可靠性水平的评估结果。比如,电化学储能和物理储能等不同类型储能的调频、爬坡、备用调节性能各不相同,未来一段时间内省级电网内不同类型储能规模占比的变化,也会对储能整体可靠性水平指标的计算结果产生不确定性影响。因此,在计算主体可靠性水平指标时,可能存在不确定性和模糊性。本文采用了模糊TOPSIS方法(fuzzy technique for order preference by similarity to ideal solution)来解决主体可靠性水平模糊性评估的问题。该方法基于模糊数运算(通常使用三角模糊数表示数据)进行计算。模糊TOPSIS方法是传统TOPSIS方法的模糊扩展,其基于“最优方案应最接近正理想解和最远离负理想解”的原则,对同一类型的多个差异性主体可靠性水平指标进行计算。该方法的核心步骤包括构建标准化决策矩阵、确定正理想解和负理想解、计算模糊距离以及计算相对接近度,具体如图3所示。
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