Adjustable capability of the distributed energy system: Definition, framework, and evaluation model

The adjustable capability of distributed energy systems responding to the incentives of the upper energy supply system has been significantly improved by energy storage and renewable energy technologies. Most existing research focuses on evaluating the flexibility of distributed energy system itself or the demand response potential of end-users, but there is no specific model which takes the distributed energy system as an integrated load and evaluates its adjustable capability from the perspective of the upper energy supply system. To fill the research gap, this paper defines the adjustable capability of distributed energy systems, describes its characteristics, and proposes a unified evaluation model. Then, from the perspective of energy demand and supply sides, it quantifies the impact of each influential factor in different energy links on the adjustable capability and studies the interactive mechanism between devices within the system. Thereafter, the adjustable capability of distributed energy systems under typical scenarios at a single moment is evaluated, and the impact of economic constraints on the adjustable capability is also extensively analyzed. Accordingly, this paper proposes a sequential recurrence method to evaluate the adjustable capability of distributed energy systems against three different initial states: unknown initial state, fixed initial state, uncertain initial state. Finally, the adjustable capability concept is demonstrated on a practical industrial park to verify the effectiveness and practicability. This study deepens the connection between distributed energy systems and upper energy supply system in the Energy Internet at the energy information level. Which enables distributed energy system to quantize its energy demand range for the upper energy supply system and realize its own reliable operation and rolling optimization. In addition, this evaluation method allows upper energy supply system to plan, overhaul and dispatch more economically and reliably on the basis of understanding the energy demand of distributed energy system. Moreover, upper energy supply system can formulate the demand response strategy with the maximum revenue by balancing the size of adjustable capability interval of distributed energy system and the investment cost of demand response.