Distributed control and operation of decarbonized and informatized low-voltage networks with multi-energy resources

Abstract

Driven by environmental concerns, low-voltage networks are undergoing a significant transformation of decarbonization with the growing integration of renewable energy resources. Meanwhile, the deployment of information and communication technology (ICT) empowers the informatization of low-voltage networks to support intelligent functionalities. However, despite benefits achieved under transformations of decarbonization and informatization, new challenges are posed which cannot be tackled efficiently and effectively by using centralized control and operational schemes. To address arising challenges, this thesis focuses on the reconstruction of control strategies and operational schemes for future decarbonized and informatized low-voltage networks. The thesis firstly gives attention to ensure the stable and economic operation of the microgrid (MG). Due to the distributed nature of inverter-based distributed energy resources (DERs) in the MG, a distributed secondary control structure is favorable to enhance the performance and scalability of MGs. Pinning-based control techniques are adopted to develop a distributed secondary frequency and voltage control for islanded MGs to maintain stable operation under frequent power fluctuations. Moreover, the impact of the communication topology on the pinning-based secondary control is examined analytically. Then the communication network for the MG is designed to minimize the communication cost and achieve control convergence. Furthermore, the islanded MG is divided into some nanogrids (NGs) for the sake of effective management for DERs. Based on the MG partition, the thesis then investigates how NGs can be coordinated to participate in peer-to-peer trading and provide ancillary service provision in an islanded MG. A multi-market paradigm is designed to realize the trading of both energy and ancillary service among NGs and optimal offering strategies are developed to maximize the profit of producer NGs in three consecutive markets in different time phases. Moreover, a distributed real-time operation is enabled so that the frequency regulation service can be provided economically. Resulted from intermittency of renewable energies, an increasing number of minor and temporary voltage violations will be experienced in a highly renewable penetrated distributed network. The thesis further develops a fully distributed voltage regulation scheme for dominantly resistive distribution networks, considering the financial incentives of the electric vehicle fleet (EVF). It includes an optimal planning stage for the planning of EVF charging/discharging and a distributed regulation stage for real-time voltage regulation. Based on the parallel-consensus control, the voltage can be collectively regulated through P and Q support from EVFs in a fully distributed and economical manner. Extensive applications of ICT require exceptional awareness of cybersecurity-related issues in the distribution network. Last but not least, the thesis focuses on the eavesdropping attack to address the pressing demand for privacy preservation in distributed schemes. A privacy-preserving distributed energy management system (EMS) for distribution network is presented, fulfilling the core task to prevent information disclosure of each agent during the information exchange. Secure exchange protocols based on the homomorphic cryptosystem are developed so that the leakage of agents’ private information (price information, power usage data, and power utilization ratio) in iterative communications can be effectively prevented.