Grid inverters - Additional parameters

Most of the parameters on this sheet are informative only; some (in bold) denote special features.


*Multi-MPPT*	Some inverters have several MPPT inputs, which allow connection of PV arrays of different sizes, module types, or orientations. Normally each MPPT input may be considered as half an inverter (for a 2-MPPT configuration); these are completely independent and have half the nominal power and do not share the power capacity of the full inverter. This is a limitation of PVsyst simulation capabilities compared to the manufacturer's specifications.
*Unbalanced MPPT*	When you check this option, you have the ability to define 2 different MPPT inputs (as available with some recent inverters on the market, such as the SMA Tripower series). PVsyst defines the main and secondary MPPT inputs. See Inverter model: Multi-MPPT.
Max ISC current	When defining unbalanced MPPT, manufacturers typically specify the different inputs by their maximum ISC current, not power limitations. Therefore, after sizing, PVsyst allocates a nominal power to each input according to the ratio of the nominal PV power of each sub-array.
Number of DC inputs	Informative only; indicates the acceptable number of strings (connectors) but is not used by PVsyst. Do not confuse with the number of MPPT inputs.
String inverter	Some manufacturers offer inverters that can directly receive string terminals without intermediate circuitry. The device includes all protections normally mounted in a junction box on the roof (fuses, non-return diodes, overvoltage protections). The number of "String" inputs should correspond to the actual number of strings.
*Transformer*	May be transformerless (for best efficiencies), low frequency, or high frequency transformers. The transformer is required for some applications, such as arrays of amorphous modules (degradation of the TiO2 electrode) or some older back-contact modules (which must be polarized with respect to ground voltage).
*Master/Slave*	Some inverters may operate in "Master/Slave" mode, where one ensures MPP tracking and transmits this information to the other(s). This allows you to activate the required number of devices, improving efficiency at lower powers. In this configuration, the full array must be connected to all devices simultaneously in parallel. For master/slave operation, you must define the power threshold above which the second device will be turned ON. See Inverter model: Multi-MPPT.
Internal Master/Slave	Many large inverters are marketed as "master/slave" devices. These are assemblies of standard units of defined power that operate internally in master/slave mode. This operating mode results in a very good efficiency curve (of the entire device) with a sharp elbow at low powers. These should not be treated as "Master/Slave" in the simulation process, as this behavior is already accounted for in the efficiency.
*Auxiliaries consumption*	Consumption from fans or other accessory devices, to be deducted from the inverter output available energy. For the simulation, auxiliaries consumption is not automatic, even if defined here; it must be explicitly specified in the "Detailed Losses" section.
Night consumption	Usually negligible; if less than 0.05%, it will not appear on the loss diagram.
Other specifications	Provides additional information about the device's configuration, features, and protections, not used in the simulation.
Isolation Monitoring	A continuous check of the isolation of the PV array with respect to ground.
DC Switch	Indicates whether the device includes this feature; otherwise, it must be provided externally on all DC inputs.
AC Switch	Indicates whether the device includes this feature; otherwise, it must be provided externally.
AC Disconnect adjust	The inverter must cut the AC connection immediately when the grid voltage goes outside a given AC voltage range (in Europe, 230 V or 400 V ±6% and -10%). This feature allows adjustment of these limits.
ENS	Indicates that the shutdown security in case of grid failure operates based on grid impedance measurement. This system is mandatory in Germany.