Switching Operations in the Automatic Transfer Switching Device for Sunny Boy Smart Energy
This section describes the operating principle of the automatic transfer switching device as exemplified by the single-phase battery-backup system with Sunny Boy Smart Energy and with all-pole disconnection. When looking at the other automatic transfer switching devices, the following differences are important:
In battery-backup systems without all-pole disconnection, no grounding device is required.
Phase coupling is optional.
Operating principle of the tie switch - behavior in the event of grid failure
The tie switch disconnects the battery-backup grid from the utility grid in the event of grid failure or if the utility grid has breached the thresholds for voltage and frequency.
The Sunny Boy Smart Energy detects a grid failure as soon as the grid voltage falls below a defined threshold. After the grid failure has been detected, the tie switch disconnects the battery-backup system from the utility grid and forms a battery-backup grid.
Depending on the grid configuration and product configuration, the contactor connects the neutral conductor with the ground potential of the battery-backup grid.
Monitoring the feedback contact enables the safe activation of the supply grid to the battery-backup grid. If the activation was successful, the connected loads are supplied in the battery-backup grid.
Operating principle of the tie switch - behavior when grid power is restored
As soon as the utility grid is available again, the Sunny Boy Smart Energy detects this.
When the set grid monitoring time has been completed successfully, the inverter stops the battery-backup operation and stops the supply of the grid isolation contactor.
After the interruption, the Sunny Boy Smart Energy is then reconnected to the utility grid and the loads are powered by the utility grid again.
The time until the battery-backup system is connected with the utility grid varies due to a mandatory waiting time. This waiting time is stored in a country data set of the Sunny Boy Smart Energy according to the country-specific requirements.
Function of the grounding device
In some countries (e.g. in certain grid areas in Germany) the neutral conductor of the battery-backup grid must not remain connected to the utility grid in the event of a grid failure. That is why the neutral conductor must be connected with the ground potential of the battery-backup grid in battery-backup operation.
Operating principle phase coupling
The phase coupling contactor is controlled by the inverter. Depending on the backup product, the phase coupling is activated automatically in the event of a grid failure and connects the unsupplied line conductors with the supplied line conductors.
In the event of a grid failure, the line conductor that is connected with the Sunny Boy Smart Energy is supplied with voltage first. Then the phase coupling combines the two other line conductors.
When the utility grid is available again, the phase coupling disconnects the combined line conductors.