Controller functions
The controller's operational functions are mainly for protecting 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), using thresholds on the battery voltage.
Definition in PVsyst
Historically, in small systems, the controller was a small device that ensured charging and discharging control with direct coupling to the PV modules. Manufacturers later included a power conditioning function to ensure maximum power tracking (MPPT). These controllers very rarely include a back-up generator control. This is the main definition of a controller for stand-alone systems in PVsyst.
However, in modern systems with higher power, manufacturers offer independent devices for charging the battery from the PV array (Solar charger) and Battery inverters for discharging energy. The charging control function is included in the solar charger, whereas the discharging control is provided by the inverter.
In PVsyst, we maintain the "older" structure to also describe "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 (that is, the absolute maximum power required from the user).
It is possible to modify this maximum discharging current value, which will be stored with the system's parameters. The same applies to any back-up control.