In power systems, flexibility can be defined as the ability to cope with variability and uncertainty in generation and demand. The ongoing energy transition is affecting how much flexibility is required, but also who should provide it: some existing solutions are being phased out, while new solutions’ entire business models are based on providing flexibility (e.g. storage or demand response). With the intention of condensing information and rationalising debates, a significant number of methods have been proposed to quantify various facets of flexibility; this paper reviews and classifies them depending on the question they attempt to address. We propose a pair of novel tools to quantify a comparatively unexplored aspect of flexibility: who is providing it. These frequency spectrum analysis based tools separately quantify flexibility provision on the annual, weekly and daily timescales. The tools’ effectiveness and versatility is demonstrated through several example applications, analysing both historical and prospective power systems, in several geographical locations with contrasting characteristics. The proposed tools are of particular value to the capacity expansion planner, allowing them to quantify changes in flexibility provision as new solutions are introduced, or as carbon taxes, generation and interconnector capacities evolve.

在电力系统中，灵活性可以定义为应对发电和需求中的可变性和不确定性的能力。正在进行的能源转型正在影响所需的灵活性，以及​​将由谁提供：某些现有解决方案正在逐步淘汰，而新解决方案的整个业务模型都基于提供灵活性（例如存储或需求响应）。为了浓缩信息和合理化辩论，已经提出了许多方法来量化灵活性的各个方面。本文根据他们尝试解决的问题对其进行了分类。我们提出了一对新颖的工具来量化灵活性的一个相对未开发的方面：谁来提供它。这些基于频谱分析的工具分别在年度，每周和每天的时标上量化灵活性的提供。该工具的有效性和多功能性通过几个示例应用程序进行了演示，这些应用程序分析了具有不同特征的多个地理位置的历史和未来电力系统。拟议的工具对容量扩展计划者具有特殊价值，使它们能够量化随着新解决方案的引入或随着碳税，发电和互连能力的发展，灵活性提供的变化。