How can I include an inverter in a stand-alone system ?

[André Mermoud]

In PVsyst, the definition of the user's needs is specified in terms of energy.

Now this energy may be used in any way. Either directly by DC appliances, or by AC appliances after an inverter.

The load energy specified in PVsyst is the DC energy before the inverter. If you want to use an inverter you should estimate externally the required DC energy, taking the efficiency and the stand-by losses into account.

In fact the main information expected from the Stand-alone systems simulation is the energy balance between the PV production, the battery storage and the energy use (including a possible genset). The inverter is not an essential point in this evaluation.

An inverter for a stand-alone system is a completely different device than an inverter for grid-connected systems:

- For a grid-connected system, the input performs the MPP tracking on the I/V curve of the PV array; and at any time, the converted power is determined by the suns' availability.

- For a stand-alone system, the input works at fixed-voltage (the battery voltage) with an "unlimited" current or power; the power is according to the instantaneous user's needs.

We have deeply renewed the treatment of the Stand-alone systems for the version 6.40. Inverters devices will be defined soon.

This requires to define a new component type, and the corresponding database.