Automatic backup transfer

When the grid fails, automatic backup transfer separates the backup grid from the utility grid so that a battery system can keep supplying the loads. In an SMA Sunny Island backup system, loads and PV go unsupplied for roughly five to seven seconds after disconnection. After that the PV system can synchronize to the backup grid and feed in. When the utility grid comes back, the backup system first synchronizes with it, and then the transfer switch reconnects the backup grid. In SMA systems built around Sunny Boy Storage, the SMA Backup Unit Controller inside each transfer switching device operates the contactors as the storage inverter directs. For SMA, the parameter Operation.BckTyp must be set to Automatic backup operation before the device will switch over automatically on grid failure. Its other settings are Off and Backup Secure Operation. The Enphase IQ System Controller acts as the microgrid interconnect device. It detects a grid failure and moves the home from grid power to backup power automatically. For whole-home backup, the IQ System Controller is installed on the line side of main load panels rated up to 200 A. It can also work with a generator, with or without an IQ Battery. The Solis RHI-1P HVES-5G hybrid inverter lists a backup switch time under 10 ms without an ATR and under 300 ms with an ATR connected.