Controller functions
The controller' functions in operation are mainly for the protection of the battery:
| Status | Description |
|---|---|
| Charging ON / OFF | Disconnect the PV array when the battery is full, and reconnect it when necessary, |
| Discharge OFF / ON | Disconnect the load when the battery is empty, and reconnect it when possible, |
| Backup ON / OFF | If a back-up generator is available, start it when the battery is empty, and stop it when sufficiently charged. |
These operations should be performed according to the battery's state of charge (SOC), involving thresholds on the battery voltage.
Definition in PVsyst
Historically, and for little systems, the controller was a little device ensuring the charge and discharge control, with a direct coupling to the PV modules.
Then the manufacturers included a power conditioning function, ensuring the maximum power tracking (MPPT).
Very rarely, these controllers are equipped with a control of a Back-up generator.
This is the main definition of a controller for stand-alone systems in PVsyst.
However in modern systems with higher power, manufacturers propose independent devices for the charge of the battery from the PV array (Solar charger) and Battery inverters for the use of the energy. The Charging control function is included in the Solar charger, when the discharging control is ensured by the inverter.
In PVsyst, we keep the "old" structure for also describing the "Solar chargers".
In these PVsyst definitions, the discharging control is not defined within the parameters. When included in a system, it will be adjusted to the system conditions (i.e. the absolute max. power required from the user).
It is possible to modify this Max. discharging current value, which will be stored with the system's parameters. The same holds for the eventual Back-up control.