# Grid-Forming Storage Deep Dive: How to Build Voltage/Frequency with No Grid With no stable utility grid, the key question is who builds the voltage/frequency reference. Grid-forming principles, redundant paralleling and VGRID cases. The core problem off-grid/islands face With no stable utility grid, the key question is who builds the voltage and frequency reference. That falls to the **grid-forming PCS**. What grid-forming (GFM) does A grid-forming PCS actively builds the reference, supports multi-unit paralleling and microgrid operation with diesel/PV. Unlike off-grid (a state), grid-forming is a capability. Operating sequence (PV-wind-storage-diesel) Renewables first: PV/wind generate. PCS stabilises V/f + battery balances power. Low SOC → start diesel. Recovered → exit diesel. VGRID grid-forming and cases [SP125HCPS](/en/product/sp125hcps) parallels up to 15 units off-grid; [Leona-H135K](/en/product/sp135hapss) 20+ units. The [Maldives island grid-forming project](/en/cases) uses 18×30kW PCS (3 per unit, 6 units); PCS sustain the reference, units need no inter-comms, diesel joins/leaves freely, and any unit exit doesn’t break the system. ## Biggest difference: grid-forming vs grid-following? Grid-following needs an external reference; grid-forming builds it and runs independently off-grid with multi-unit support. ## Why pursue modular redundancy in grid-forming? Any unit exit must not break the system (Maldives); achieved by stable reference + redundancy + seamless multi-source coordination. ## How to exceed the 15-unit limit? Beyond standard paralleling, use a system-level PCC controller + contactor scheme (e.g. 2.5MW mine, 20 PCS). ## Does grid-forming help power quality? Yes — it provides virtual inertia and voltage support, improving frequency/voltage stability in weak grids.