Unlocking energy flexibility potential in user-friendly buildings: a bi-level hybrid economic model predictive control strategy

Recently, there is growing interest in exploring demand-side energy flexibility to maintain the power balance of residential building energy systems. However, the flexibility potential of shiftable appliances has not been fully explored. The shiftable appliances are devices whose operating periods can be adjusted within a predefined flexible time-window. They are important energy flexibility sources that can be leveraged to optimize energy consumption patterns and enhance the responsiveness of demand-side management strategies. To this end, this paper first establishes a nonlinear model for the studied residential building energy system. Then a bi-level hybrid economic model predictive control (EMPC) strategy, which is composed of a mixed-integer EMPC in the upper layer and a tracking MPC in the lower layer, is designed to achieve the residential building energy system optimal operation and unlock the flexibility and economic potential within the system. Moreover, a rolling flexible time-window is introduced through a dynamically updated constraint matrix, which enables the exploration of shiftable appliances energy flexibility. Three categories of performance indices: user comfort, economic efficiency and demand-side energy flexibility, are introduced to evaluate the effectiveness of the proposed bi-level hybrid EMPC strategy quantitatively. The simulation results show that compared with the rule-based control, the proposed control strategy decreases the electricity costs by 7% and improves the load shifting flexibility by 15% under normal weather condition. Even under extreme weather condition the proposed strategy can fully utilize energy flexibility sources, with a 17% reduction in electricity costs compared with the rule-based control. The impacts of different flexibility source configuration are also investigated, providing insights into how they influence system flexibility, cost-effectiveness, and user comfort.