Cost-effective solution for the non-firm grid connection of Low Voltage Generators (Grid ExpanDER)

Roseau Technologies, a French software startup established in 2018 by three experts with  backgrounds in both academic research and corporate R&D, has a core focus on software engineering and electrical engineering. With a team of 12 individuals, the company specialises in crafting software for modelling, simulating, optimising, supervising, and controlling electrical distribution networks. Our extensive work in the realm of “non-firm grid connections” under a research grant from the French Energy Transition Agency (ADEME) has given birth to the Grid ExpanDER software. This innovative technology leverages existing smart metering infrastructure to implement “non-firm connections” in low voltage (LV) networks.

Non-firm grid connections represent contractual agreements between Distribution System Operators (DSOs) and customers. These agreements allow DSOs to curtail customer power consumption when necessary to prevent grid congestion, providing a faster and cost-effective connection option. They are particularly beneficial for generators, reducing grid connection costs and facilitating the integration of renewable sources.

While non-firm grid connections are currently used for medium voltage (MV) generators, their application at the low voltage (LV) level remains untapped. Roseau Technologies aims to address these challenges by utilising existing smart metering infrastructure, designing a controller to operate within LV grids, and consolidating data to assess network conditions and curtailment needs. The Grid ExpanDER software was developed for this purpose.

The Grid ExpanDER software underwent rigorous testing and validation within Roseau Technologies' in-house laboratory setup. To further validate it at scale, we successfully applied for access to the SysTec infrastructure at the Fraunhofer IEE in Kassel, Germany, through the ERIGrid 2.0 program, conducting two visits in 2022 and 2023.

The experiments at the SysTec facility involved a low voltage (LV) network consisting of three houses, each equipped with a photovoltaic (PV) generator, which could be connected to LV cables of varying sizes and length. Real smart meters using G3-PLC technology were also employed, as well as a G3 PLC gateway known as nBox-SG. Additional monitoring equipment (Janitza UMG-604 pro meters, Eastron SDM630MCT-ML) were used to measure voltages, currents, and powers at a 15-second sampling rate.

The main issue that was met during the experiments was the occurrence of PLC communication problems. These problems were solved after identifying that their root cause was a faulty PV inverter that was emitting strong electromagnetic noise in the PLC frequency band.

The experiments then ran smoothly and confirmed that the Grid ExpanDER solution was working as intended in the SysTec environment, hence with more realism than the experiments that Roseau Technologies had previously conducted on their internal reduced-scale setup. The experiments at SysTec also shed some light on the imperfections of the control, showing that moderate voltage excursions were unavoidable with the purely centralized controller that was experimented during the project. Future work on the Grid ExpanDER project will focus on addressing this issue.