A decentralized approach for enabling advanced ancillary services through distributed energy sources

This thesis reports the results carried out by the author during the three-year activities of the XXXV cycle of the Ph.D. course in Electrical and Information Engineering at Politecnico di Bari. The main goal of this work was to implement a decentralized approach to enable the provision of Ancillary Services (AS) by means of Distributed Energy Resources (DERs). As a first step, an analysis of Regulations, Directives, and Network Codes at the national and European level was carried out to define the future framework of the electricity market. In addition, papers and technical reports concerning eight European projects, such as SmarNet, CoordiNet, FLEXCoop, OSMOSE, inteGRIDy, eDREAM, ADDRESS, and evolvDSO have been analyzed with the aim to define the state of the art about the provision of AS by means of DERs. In particular, a set of coordination schemes was identified from those proposed in the literature to coordinate the use of DERs among Transmission System Operators (TSOs) and Distribution System Operators (DSOs). These coordination schemes are classified into centralized and decentralized architectures, depending on the possibility of System Operators of managing their respective networks. In addition, the main methodologies proposed in the literature to perform optimal dispatch of flexibility resources in a TSO-DSO coordination framework, taking technical and grid constraints into account, have been identified and presented. In order to enable DERs in AS provision and coordinate system operators in their usage, a few methodologies suitable for decentralized architectures were developed and presented in this work. In particular, a new algorithm based on a three-phase optimal power flow routine for mapping the flexibility area at the point of interconnection (POI) between transmission and distribution grids was provided. Furthermore, two alternative methodologies to aggregate flexibility resources located in distribution networks interfaced with the TN in multiple POIs were described. In addition, a Benders decomposition algorithm able to optimize TN and DN flexibility resources for congestion management in a few decentralized coordination schemes was also implemented. The proposed methodologies were validated by means of simulation tests conducted on a power system including transmission and distribution grids. The last part of this thesis investigated how innovative grid services, such as Synthetic Inertia (SI) and Fast Frequency Response (FFR), may be also provided through fast control dispatchable resources located at the distribution grid level. With this aim, a low-cost controller for end-user applications able to generate a SI law for dispatchable DERs was developed and tested through Power Hardware-in-the-Loop (PHIL) tests. Similarly, PHIL tests were also carried out to investigate the capability of LED lamps of public lighting systems to be controlled with the aim to provide SI and FFR actions. Experimental results validated the proposed decentralized approaches.