Abstract
In recent years, the installation of residential Distributed Energy Resources (DER) that produce (mainly rooftop photovoltaics usually bundled with battery system) or consume (electric heat pumps, controllable loads, electric vehicles) electric power is continuously increasing in Low Voltage (LV) distribution networks. Several technical challenges may arise through the massive integration of DER, which have to be addressed by the distribution grid operator. However, DER can provide certain degree of flexibility to the operation of distribution grids, which is generally performed with temporal shifting of energy to be consumed or injected. This work advances a horizon optimization control framework which aims to efficiently schedule the LV network’s operation in day-ahead scale coordinating multiple DER. The main objectives of the proposed control is to ensure secure LV grid operation in the sense of admissible voltage bounds and rated loading conditions for the secondary transformer. The proposed methodology leans on a multi-period three-phase Optimal Power Flow (OPF) addressed as a nonlinear optimization problem. The resulting horizon control scheme is validated within an LV distribution network through multiple case scenarios with high microgeneration and electric vehicle integration providing admissible voltage limits and avoiding unnecessary active power curtailments.
Highlights
Nowadays, an increasing number of small-scale units, typically referred to Distributed EnergyResources (DER), is connected along the Low Voltage (LV) distribution networks posing several technical challenges, whilst bringing novel and diverse opportunities
The scenarios are selected in order to validate that the Multi-Period AC-OPF (MACOPF) could allow high integration of microgeneration avoiding overvoltages and overloading of the transformer; secondly, mixed scenarios of Distributed Energy Resources (DER) integration including Electric Vehicles (EV) are assessed by the coordinated control amongst them
The available active measures for operational purposes are active power control of the centralized three-phase Battery Storage System (BESS), the coordinated charging of the EVs in addition to V2G mode of operation where both are considered once the EV is available, and the control active and reactive power of the microgeneration
Summary
An increasing number of small-scale units, typically referred to Distributed Energy. A three-phase multi-period OPF based on the exact (i.e., nonlinear) AC power flows is proposed, incorporating multiple DER within the operation of the distribution grid. For any three-phase BESS the different phases are hereby considered to follow the same mode of operation; the mathematical expression is comprised of three single-batteries installed in the different phases, coupled with the equality constraints for their active and reactive power injections as in Equation (3): A. When the owner of an EV desires to provide a signal of flexibility, the time interval when the estimated trip will occur together with the estimated consumed energy should be dispatched to the DSO These two signals are captured for each controllable (i.e., willing to be charged in concordance to the smart charging scheme) with [ytrip ] that is added to discharge the EV and Etr , where ntr corresponds to the number of trips for an EV.
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