Hierarchical Microenergy Hub Sizing and Placement in Integrated Electricity and Natural Gas Distribution Systems

The integration of different energy carriers is a key factor to improve the energy network performance. A micro-energy hub (μEH) concept has recently been proposed in the integrated electricity and natural gas distribution systems (IENGDSs), for generating, converting, storing, and managing different types of energy at the customer level. To improve the performance of μEH, this paper proposes a hierarchical optimization-based model to optimize the sizes of μEH components and locations of μEHs in the IENGDS. The operation and structural sizing constraints of the μEHs are first determined. Then the optimal electricity network buses and natural gas nodes for installing μEHs are determined, considering the operational constraints of IENGDS. The objective in both steps is to minimize operation and investment costs. Moreover, the impacts of seasonal climate changes on energy demands and prices are considered during the planning horizon. Furthermore, the uncertainties in demands and renewable energy generation are quantified with a two-stage stochastic programming framework. The effectiveness of the proposed method is evaluated on an IENGDS that consists of an IEEE 33-bus distribution system and a Belgian 20-node natural gas system. Numerical simulations demonstrate that the optimal hierarchical planning model can improve total line losses and reduce the total purchased electricity from the upstream network and total imported natural gas from gas wells. The simulation results show that if the hierarchical optimization process is not performed in determining optimal placement of μEHs, then IENGDS may operate with electricity network congestion or natural gas pressure violations during the planning horizon.