Simulation report on development of AC/DC Hybrid Microgrids in parallel with existing distribution grids
Creators: name: Strehn, Simon
name: Jambrich, Gerhard
Publisher: name: The HYPERRIDE Consortium
Year: 2024
Subjects: DC microgrids
Hybrid AC-DC grids
Grid planning
Deliverable
European Union (EU)
H2020
Project
HYPERRIDE
GA 957788

description: The incorporation of a greater number of Renewable Energy Sources (RES), the transition towards Distributed Energy Generation (DEG), and the evolving energy consumption patterns resulting from the electrification of transportation are set to reshape both electricity production and demand. The impact of these changes is particularly notable in the Low Voltage Distribution Grid (LVDG), where the increasing prevalence of Electric Vehicle (EV), the integration of small to medium-sized distributed RES like Photovoltaic (PV) systems, and the utilization of energy storage solutions such as Battery Energy Storage System (BESS) are transforming thelandscape.

Today, a significant proportion of devices connected to the LVDG operate on Direct Current (DC). This includes powering common everyday devices like computers, cellphones, and EVs. DC offers the advantage of energy storage capability and is unaffected by reactive power and is not requiring synchronization. These characteristics simplify the control of DC systems. RES such as PV systems and fuel cells inherently produce DC power, making their integration into a DC network more efficient. The partial operation of the distribution grid using DC instead of Alternating Current (AC) has emerged as a viable strategy for cost-effective management in the context of future grid scenarios aligned with international decarbonization objectives.

Utilizing a simulation tool for techno-economic analysis with synthetic test grid models, it has been demonstrated that the conversion of Low Voltage Alternating Current (LVAC) grid feeders to a DC configuration represents a viable solution for alleviating overloading and reducing voltage fluctuations. These issues are primarily induced by factors such as the integration of EVs, PV, and heightened energy demand. The simulation tool showcases the flexibility of rapidly hybridizing complex grid models within DIgSILENT Power Factory. It highlights the potential advantages of integrating DC technology into Low Voltage (LV) grids, particularly when near-capacity limits are reached.

A simulation model was developed based on the DC pilot installation in Terni, encompassing the nearest Medium Voltage (MV) feeder from the public grid. It integrates various grid planning tools and conducts Quasi Dynamic Simulation (QDS). The Terni pilot site was simulated using Power Factory because the existing simulation tool lacked the capability to model the Alternating Current and Direct Current (ACDC) microgrid with two connection points via transformers. The analysis has brought to light that the AFE plays a decisive role in AC grid support by the DC grid, as shown by the current AC grid and the proposed DC configuration. In thecontext of this demonstration site, it is essential for the converters to possess the capability to supply reactive power to effectively support the AC grid.

As part of our efforts, we conducted an extensive investigation with the primary objective of identifying the most suitable configuration for the ACDC microgrid. Our ultimate goal was to maximize self-consumption while minimizing reliance on the AC grid. The resulting optimal configuration not only allowed for the integration of more AC loads but also reduced the required battery power output.