Abstract
This paper proposes a coordinated two-stage real-time market mechanism in an unbalanced distribution system which can utilize flexibility service from home energy management system (HEMS) to alleviate line congestion, voltage violation, and substation-level power imbalance. At the grid level, the distribution system operator (DSO) computes the distribution locational marginal prices (DLMP) and its energy, loss, congestion, and voltage violation components through comprehensive sensitivity analyses. By using the DLMP components in a first-stage optimization problem, the DSO generates two price signals and sends them to HEMS to seek flexibility service. In response to the request of DSO, each home-level HEMS computes a flexibility range by incorporating the prices of DSO in its own optimization problem. Due to future uncertainties, the HEMS optimization problem is modeled as an adaptive dynamic programming (ADP) to minimize the total expected cost and discomfort of the household over a forward-looking horizon. The flexibility range of each HEMS is then used by the DSO in a second-stage optimization problem to determine new optimal dispatch points which ensure the efficient, reliable, and congestion-free operation of the distribution system. Lastly, the second-stage dispatch points are used by each HEMS to constrain its maximum consumption level in a final ADP to assign consumption level of major appliances such as energy storage, heating, ventilation and air-conditioning, and water heater. The proposed method is validated on an IEEE 69-bus system with a large number of regular and HEMS-equipped homes in each phase.
Highlights
In recent years, distribution systems have experienced an unprecedented growth in the deployment of distributed energy resources (DERs) including photovoltaic (PV)equipped and smart homes
Operation by causing congestions [2, 11]. It is crucial for a distribution system operator (DSO) to design congestion mitigation strategies in three-phase unbalanced distribution systems and coordinate it with the way flexibility service is utilized from price-responsive end users
Determines the occurence of a congestion or voltage violation, it seeks flexibility by sending the lower and upper distribution locational marginal price (DLMP), p/p;i and p/p;i, where p/p;i is the sum of energy and loss components (p/p;i 1⁄4 pEp;;0/ þ pLp;;i/) and p/p;i is the sum of all DLMP components (p/p;i 1⁄4 pEp;;0/ þ pLp;;i/ þ pVp;;i/ þ pCp;;i/), to each home energy management system (HEMS)-equipped home h served by phase /
Summary
Distribution systems have experienced an unprecedented growth in the deployment of distributed energy resources (DERs) including photovoltaic (PV)equipped and smart homes. While most of the existing literature use ‘‘DC’’ power flow and a flat voltage profile to compute only real power DLMPs [2, 3, 8, 11], or consider balanced distribution systems [4, 29], we propose a real-time DSO optimization model that can determine real and reactive power DLMPs in three phases of an unbalanced distribution system, and utilize a coordinated flexibility service from HEMS to alleviate operation issues such as voltage violations and line congestion in different phases. 2) At the grid level, we propose a two-stage real-time operation framework using which a DSO can implement a coordinated flexibility service among a large number of HEMS-equipped homes while alleviating congestion, voltage violations, and substation-level power imbalance.
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