Modelling flexibility from distributed energy resources
A number of distributed energy resources (DER) are emerging at many levels of the distribution network, including various forms of embedded generation, energy storage based on different technologies and energy vectors, and demand response. With large-scale, centralized conventional technologies disappearing from the system, such DER become most promising options for providing flexibility and ancillary services and take up part of the overall system control to deal with large-scale penetration of Renewable Energy Sources (RES). Increasing deployment of DER thus creates both opportunities and technical challenges in system-wide planning and control. DER could in fact provide reliable and low-cost demand shifting, load and supply balancing flexibility, and various grid services, consequently reducing the cost of investing in generation and network peak capacity and enhancing local and system-level flexibility and resilience. However, integrating large amounts of DER also change the traditional one-way power flows' direction - from transmission to distribution networks to customers - into two-way power flows. Hence, visibility and coordination of DER for system-wide operation become essential to maximise the benefits of flexibility of and from DER, for instance considering technical (e.g., thermal and voltage) envelops of aggregated DER to increase the hosting capability of the local network and reduce interventions on the customer sides. On the above premises, this paper aims at reporting on the first year of work carried out by WG C6/C2.34 ""Flexibility provision from DER"", which was created to gain new insights into the concept of flexibility and relevant grid and market services that DER could provide from both technical and commercial perspectives and at the levels of local networks as well as whole-system operation. Specific aspects of DER flexibility addressed in this work include: ● Reviewing drivers and new requirements for flexibility at different stages of power system planning and operation, from the whole-system to the local network. ● Providing a definition and characterization of the concept of DER flexibility that is most suitable in the context of renewables integration. ● Compiling preliminary information from selected technologies on the potential of DER to provide flexibility over different time scales, and in different forms, including distributed generation, different forms and technologies of energy storage, electric vehicles, and residential, commercial and industrial demand response. ● Discuss the specific but increasingly important case of DER flexibility in isolated systems.