Flexibility Provisions from Energy Hubs for Sustainable Energy Systems

Power systems have some inherent level of flexibility built into the system, to meet the continuous mismatches between the supply and demand. Variability and uncertainty are not new to power systems as loads change over time and generators can fail in unpredictable manners. Penetration of renewable resources and plug in electric vehicles (PEVs) can make this mismatch even more difficult to meet and new flexibility resources will be needed to supplement the flexibility capabilities of the existing system. There are many options to provide flexibility at the distribution system level, but their potential have not been fully utilized. This thesis addresses some of the pertinent issues relating to flexibility provisions from energy hubs. In the first research problem, an electric vehicle charging facility (EVCF) is transformed to operate as a smart energy hub in order to build its flexibility provision. The EVCF demand mostly occurs during the evening, coinciding with the peak demand, and has no flexibility because of the short stay of PEVs at the charging facility. From the system planner’s and operator’s point of view, such transformation of the EVCF presents a new source of flexibility to the distribution system, which could alleviate network stress and defer upgrades, and the transformation to a smart energy hub will also reduce the EVCF’s operating costs through improved energy management. A generic and novel framework is proposed to optimally design and plan an EVCF as a smart energy hub that controls the energy flow between the renewables-based generation units, the battery energy storage system (BESS), the external grid, and local consumption. The proposed framework is based on a bottom-up approach to design and planning of an EVCF, incorporating a detailed representation of vehicle mobility statistics to estimate the charging load profile, and then integrating all dimensions of planning, such as technical feasibility assessment, economics, and distribution system operations impact assessment. The thesis further presents a new mathematical model to design an EVCF with distributed energy resources (DERs) to provide flexibility services in wind integrated power grids. Two different ownership structures of the EVCF and the wind generation facility iv (WGF) are presented and analyzed for the first time. The DER options considered for the EVCF design are solar photovoltaic (PV) units and BESS. The effects of wind power uncertainty on power system operations are mitigated through the designed EVCF with DERs via the upward and downward flexibility provisions. Monte Carlo simulations are used to simulate the uncertainties in PV and wind generation, and market price. In the third research problem, residential loads are transformed to residential energy hubs (REHs) to develop an inherent flexibility in their portfolios, and hence offer a wide range of benefits to the power grid, such as peak reduction, congestion relief and capacity deferral. A generic and novel framework is proposed, to simultaneously determine the optimal penetration of REHs in distribution systems and the optimal incentives to be remunerated by the local distribution company (LDC) to residential customers for flexibility provisions, considering economic benefits of both parties. The proposed framework models the relationship between the participation of residential customers in transforming their houses to REHs and the incentives to be offered by the LDC. A new concept of unloaded and loaded states of REHs is also introduced for quantifying the power availability of REHs, from which power flexibility can be provided considering the penetration of REHs in the system.