Energy Storage System Supports District Isolated from Mains Electricity for a Record 5 Hours

PCS²’s energy storage systemFollowing a test period over several months on “Concept Grid” - EDF R&D’s1 experimental platform in Seine-et-Marne - teams from French distribution system operator ERDF2 and power conversion specialists, SOCOMEC, have successfully validated the islanding of an entire district for periods up to a record 5 hours.

This operation is part of the smart solar district pilot site -Nice Grid in the south of France - an ambitious smart electricity network project that generates and stores large amounts of solar energy.

The global targets to reduce harmful emissions associated with the production of electrical power require a massive integration of renewable energy into our electricity networks. In order to support this significant integration – whilst also maintaining the quality of the networks – intelligent, decentralised systems are required to intermittently store the energy produced and to regulate distribution according to demand.

ERDF, which is spearheading the project, targeted a district comprising 8 industrial clients and 3 large photovoltaic installations, generating a total of 430 kWp. An energy storage solution has been installed with a control system specifically designed to manage the disconnection and reconnection of the district to the mains supply. In disconnected or “islanded” mode, industrial clients continue to be supplied via Socomec’s PCS²’s energy storage system and photovoltaic production.

Giovanny Diquerreau, Energy Storage Projects Director at Socomec, explains; “The Nice Grid project demonstrates that the local management of variable energy flow is achievable via efficient energy storage solutions. Socomec’s dual-function storage converters enable the photovoltaic energy available during the day to be stored in cyclic batteries, then converted and fed back into the network as usable AC current that is injected into the grid. We call this bi-directional conversion - the capability to manage energy supply to meet demand. Furthermore, these bi-directional storage converters can be programmed to operate according to a charging and discharging profile, set in advance by the energy utility provider.”

Optimised management of the connection of the district to the mains
The district is disconnected at the sub-station for the area. In the event of scheduled islanding, in order to reduce load on the main power grid, the electricity is disconnected without interruption to the district’s consumers and photovoltaic generators.

In the event of an unforeseen outage such as a power cut, Socomec’s the SUNSYS PCS² storage converter “blackstart” functionality ensures that power is restored within just a few seconds and the district is seamlessly reconnected to the mains. The Socomec control system manages the SUNSYS PCS² converters so that they are synchronised with the mains supply in terms of voltage, frequency and phase - before being reconnected.

1 R&D department of French Energy Supplier
2 French Distribution System Operator

Socomec’s “network islanding”
The result of 45 years of experience in power conversion, Socomec’s “network islanding” solution is based on the SUNSYS PCS² power conversion and storage control and command system which manages the disconnection and reconnection of the district to the mains supply.

Nice Grid is a technology showcase and pilot site for smart and environmentally sustainable grid operation and management; it is a truly disruptive innovation, islanding an entire area.
Four 66 kW SUNSYS PCS² converters have been installed in the HV-LV sub-station which manages the charging and discharging of a 620 kWh SAFT lithium ion battery container.

When operating in islanded mode, the SUNSYS PCS² systems manage the voltage and frequency of the low voltage network. When PV generation is greater than consumption, the batteries recharge, thus extending the islanding period.

What are the prospects for power storage with network islanding?
Experiments performed on the ‘network islanding’ function on an energy peninsula, such as the Provence-Alpes-Cote d’Azur region, have particular significance- especially during winter consumption peaks or in the event of bad weather resulting in power cuts.

In the medium term, network islanding is a particularly interesting economic alternative to guarantee the reliability of the electricity supply in areas where the upstream supply is unreliable, particularly in certain emerging nations and also in the case of some islands.

Finally, this storage solution will be able to supply isolated sites that are not connected to mains electricity, together with renewable energy sources, such as wind and solar, as well as diesel generators.

Tags: Socomec, Company News, Solar Industry News, e-lec.org

Image: Commissioning the 4 SUNSYS PCS² converters installed in the district’s transformer station.