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With the changes in energy structure and system configuration, the uncertainty on both the supply and demand sides of the power system will significantly increase. The approach of increasing reserves to cope with the uncertainty is becoming unsustainable both technically and economically. It is necessary to accurately characterize system flexibility and propose flexibility-oriented dispatching optimization strategies. Based on this, this paper conducts research on the evaluation system for flexibility supply-demand balance and the coordinated optimization dispatch strategy of generation-load-storage resources. Firstly, a flexibility demand-supply balance evaluation system is proposed, which covers the quantification of flexibility demand, the quantification of flexibility supply capability, and the design of flexibility metrics. Secondly, a two-stage optimization dispatching model for generation-load-storage resources is constructed. In stage 1, the optimization obtains the operating power of generation, load and storage resources to meet the load demand, while in stage 2, the flexibility supply potential is considered to optimize the redispatch power of the flexibility resources to meet the flexibility demand. Finally, simulations are conducted in a typical industrial park with generation, load, and storage resources, and the results show: 1) The quantification of flexibility demand based on the polytope form is more accurate, ensuring that the obtained flexibility supply-demand balance evaluation results can effectively support system flexibility dispatching; 2) Compared with the traditional dispatching strategy that consider reserve capacity, the operational cost of the dispatching strategy considering flexibility supply-demand characteristics in this paper decreased by 3.31%, environmental costs decreased by 4.56%, and the penalty cost for flexibility deficiency decreased by 17.37%. The research results can leverage the synergistic effect of generation -load-storage resources, achieving a scientific balance between the economy, low-carbon, and adequacy of the generation-load-storage system, and provide a scientific approach for considering flexible supply-demand balance in the power system dispatching, supporting the stable and sustainable operation of the high-penetration new energy system. • A comprehensive evaluation system for flexible supply-demand balance is designed; • The flexibility demand quantification model based on the polytope form is constructed; • A two-stage coordinated optimization dispatching model for generation-load-storage resources is constructed; • The two-stage dispatching power and costs of the generation-load-storage resources in 24 period are examined. [ABSTRACT FROM AUTHOR]

The AC / DC active distribution network (ADN) connected to a large number of renewable energy source (RES) and new loads such as EV will become the main form of the future ADN, which intensifies the volatility and uncertainty of the net load. To cope with this situation, considering various types of flexibility resources, this paper quantitatively evaluates the flexibility demand and supply in the system, and constructs a day-ahead flexible operation model of AC/DC ADN with a high proportion of RES. At first, the flexibility demand is quantified firstly by considering volatility and uncertainty comprehensively, and the conditional probability distribution of wind power volatility is obtained through the analysis of mutual information and other correlation coefficients. Then, a quantitative method to the time flexibility provided by orderly charging of electric vehicles (EVs) is proposed for the flexible cooperation with other resources. Besides, voltage source converter (VSC) with precise loss is considered as flexibility source to participate in dispatching. Furthermore, considering the preference of flexibility in different directions, a weighted node flexibility margin index is proposed. Considering the accuracy and computational efficiency, a second order cone relaxation method which is suitable for the elaborate VSC model is applied in this paper. In the end, Test results of an improved IEEE33-bus system with a three-terminal DC network show that the proposed model can improve the flexibility and reduce the operation cost of the ADN.

It is expected that an energy system faces increasing flexibility requirements in order to cope with increasing contributions from variable renewable energy sources (VRE). In general, the instant balance of temporal and spatial inequalities of the electricity system can be achieved by many compensating measures. However, a thorough and precise quantification of the flexibility demand of a VRE based energy system turns out to be a complex task. So far, literature on energy economics and engineering has provided analyses concerning various aspects of the system requirements for flexibility. Accordingly, this review paper primarily aims to categorize the scientific approaches that have been used in “flexibility demand” studies. In this context, we classify exemplary study results from the German and European energy systems into technical, economic, and market potential categories to enhance their comparability. Moreover, we conduct a methodological evaluation of the literature findings to determine further research requirements. Against this background we also discuss a conceptual framework to quantify the market potential of flexible technologies. [ABSTRACT FROM AUTHOR]