Unlocking Flexibility in Electricity Distribution Networks

Abstract

Climate change is a global challenge which has affected the decision-making process in various sectors including energy systems. Different approaches have been proposed to decrease carbon emission in energy systems. A vital tool in the transformation of energy systems towards Net-Zero emission is flexibil ity. The literature suggests different ways in enabling flexibility in an energy system, such as demand, distributed energy resources (DER), and network flex ibilities. This thesis investigates the role of flexibility in the energy networks through demand, DER, and network flexibilities. In the first part of this thesis, demand flexibility is studied through disaggregat ing the demand response to the building as the source of providing flexibility. Due to the high percentage of demand consumption by dwellings (e.g. 36% in the UK), this thesis developed different approaches in unlocking building flexibility (BF). Firstly, a systematic literature review is performed to explore the challenges and opportunities in enabling BF. Then, in order to improve the robustness of existing control methods in face of uncertainty of input data (e.g. weather forecast), a robust rolling horizon method is introduced. Finally, novel building-to-building (B2B), and building-for-grid (B4G) strategies are developed along with optimal energy management of dwellings to optimise BF while considering energy bill and occupants’ comfort as the objective functions simultaneously. This part also investigates the participation of electric vehi cles in B2B and building energy management and their role in activating BF. The proposed controller was shown to decrease computational time by 76% compared to the conventional methods, with occupants comfort having a con siderable effect on the robustness of controller (e.g. 1.3% decrease in occupants comfort increased the robustness in face of uncertainty by 10%). The electric vehicles participation in the energy management strategy decreased the energy bill by 44%. The second part of this thesis studies the flexibility in distribution networks through network reconfiguration, conservation voltage reduction, and DER as the means of flexibility in the network, load, and DERs respectively. A risk and security-constrained model predictive control is developed to improve the security of islanded microgrid considering mentioned flexibility measures. The computational efficiency of the proposed hierarchical control system in terms of accuracy and processing time is guaranteed through a mixed integer conic programming model. Then, the role of different flexibilities in the distribution level is studied for coordination of distribution networks with the transmission system. The use of conservation voltage reduction and network reconfiguration as the flexibility options decreased the emergency load curtailment in case of contingency by 3.8% and 19% respectively.