In regional Western Australia, where the utility Horizon Power is an operator of multiple remote microgrids in a wide rating range between 10 kW and 30 MW, a transition towards a renewables-dominated generation fleet is occurring at a rapid pace. Distributed Energy Resources (DER) and inverter-based generation in form of solar photovoltaics and energy storage are the prevalent type of new sources deployed in these off-grid systems. Past projects and field trials have revealed integration challenges in systems with high instantaneous penetration of renewables which include heavy reliance on a single genset for frequency control, instabilities between gensets and energy storage and unequal participation in frequency control.

A new approach is considered in which a broad range of devices will share the isochronous and frequency control function. This foresees operating battery energy storage systems in grid-forming droop mode, in parallel and in analogy to the reciprocating engines. This paper outlines the integration challenges and change in frequency control strategy and provides an overview of the investigations performed via modelling studies of the new approach, outcomes of in-factory and in-field tests, including lessons learned and benefits already being seen across a range of projects both in size and generation mix.