Technical Articles

GSES communicates factual, up-to-date and evidence-based information for publication. This includes information on the issues surrounding DC circuit breakers, earthing fundamentals, how to sell solar, and information on isolator enclosures.

Battery Charging on AC Coupled Grid Connected Battery Systems

The advent of Grid Connected Battery (GCB) systems in Australia has led to increased interest in coupling GCB systems with existing or new solar PV system to increase energy self-sufficiency. GCB systems can be connected to a PV system as a DC coupled system, where the PV array is connected through a charge controller directly to batteries, or as an AC coupled system, where the battery and the PV system are interconnected via their respective inverters. The latter configuration is especially popular to be retrofitted, because AC coupled systems require minimal reconfiguration of the pre-existing PV array and grid-connect inverter.

GCB systems need to be designed carefully to ensure that the battery bank is charged safely and reliably under all circumstances, as overcharging the battery bank can produce devastating consequences.
One issue identified is the possibility of the grid-connected PV system overcharging the battery bank in grid outage conditions when the GCB system and PV system are configured in a particular way. In this configuration, the PV generation is first delivered from the grid-connect (GC) inverter to the specified loads, and thereafter to the multimode inverter to charge the battery bank, with any excess power exported to the grid. GSES refers to this configuration as GSES Configuration 5 in its publications and course material.

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