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<< Click to Display Table of Contents >> Grid inverters, main parameters |
  
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<< Click to Display Table of Contents >> Grid inverters, main parameters |
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This sheet includes the general input and output data which are usually available on the manufacturer data sheets.
Inverter identifiers:
- Model and Manufacturer will appear in the inverter choice lists.
- Data source: Usually the manufacturer and the year of the latest update. Up to 2009 we used the yearly survey issued in PHOTON magazine.
- File name: should have the extension '.OND'. This is the primary key of the database, therefore should be unique. We use to give the form Manufacturer_Model.OND, with possible simplifications in the model.
Input side (DC, PV array)
Mandatory parameters (bold):
| VmppMin: | Minimum MPP voltage |
| VmppMax: | Maximum MPP voltage is the voltage window in which the inverter is able to search for the MPP. When sizing the array voltage (number of modules in series), this should be taken at "usual"operating conditions defined as sizing temperatures in the project (around 50°C in summer and 20°C in winter). |
| VAbsMax: | Absolute Maximum PV voltage is the absolute allowable maximum voltage under any conditions. When sizing the array, it should be compared to the array Voc under 1000 W/m² , and the lower temperature (higher voltage) possible. This is fixed at -10°C for middle Europe and may be adjusted in the Project definition. |
| Pthresh: | Power threshold is the minimum input power needed to operate. It is admitted to be the own inverter power operating consumption. Sometimes referred to as "Starting production at ..." in the datasheets. If not known, you can take it at around 1% of the nominal power. This means that your inverter will begin to produce AC electricity from an irradiance threshold of the order of 10 W/m² ... Note that PVSyst requires a minimum power threshold when automatically computing the efficiency curves. |
Secondary input voltage parameters, may be defined if available:
| Vmin_Pmax: | Minimum voltage for obtaining PNom. Some inverters cannot deliver the full nominal power when the input voltage is too low (but still over the minimum MPP voltage). This corresponds in fact to an input current limitation. PVsyst takes this limit into account during the simulation, by displacing the operating point along the I/V curve, in order to respect this current limit. |
IMax_InMPPT Current limitations on one MPPT input. This is not a "native" parameter, is is related to the preceding one Vmin_Pmax. The maximum current is indeed Pnom (IN) / Vmin_Pmax. Notice that here we have to evaluate Pnom(IN) = PNomac (OUT) / Efficiency / NbMPPT. If this maximum current corresponds to a Vmin_Pmax value outside of the MPPT range, this doesn't make sense and becomes a N/A value.
| VmppNom: | Nominal MPP voltage is sometimes specified by the manufacturer. In this case this may be an indication for the optimal number of modules in series. Weakly used in the sizing tool in the present time. |
The following parameters are often given by manufacturers, and sometimes with a contractual constraint. But they don't have a real physical meaning as they depend on the implementation (plane orientation - please see the sizing tool). They normally don't present any danger for the inverter at running time as by overload, this device adjusts the power drawn from the PV array by displacing the operating point along the I/V curve.
| PNomPV | Nominal PV power is a usually specified parameter for inverters. It may be understood as the recommended nominal STC power of the PV array. |
| PMaxPV | Maximum PV power is sometimes specified by the manufacturers. It may be understood as the absolute maximal STC power of the PV array. If this is a contractual condition you have to check the "Required" checkbox, so that the sizing tool will prevent the sizing in case of excess. |
| IMaxPV | Maximum PV current is the absolute maximal current admissible at the input of the inverter, usually the ISC current of the PV array at STC. If this is a contractual condition you have to check the "Required" checkbox, so that the sizing tool will prevent the sizing in case of excess. |
See also the inverter model: Input and Output page.
Output side (AC grid)
Although fundamental features of the inverter, the AC output parameters are not involved in the simulation results nor the system performance evaluation, which is only given in terms of Output Power (Exception: the Voltage characteristics at the AC side influence the eventual ohmic or transformer losses after the inverter).
| Mono/Tri | Usually: Mono-phased for inverters smaller than about 8 kWac, and Tri-phased for greater ones. Most grid distributors impose a limit on the phase unbalance, of the order of 3-5 kW. But of course you can distribute mono-phased inverters on each phase. |
| Freq | Grid Frequency is usually 50 Hz, but 60 Hz for the US and related zones. Many inverters are designed for accepting both frequencies, making them useable on all world markets. When choosing an inverter in PVsyst, you can ask for a selection of only 50Hz or 60Hz suited devices. |
| VNomAC | Nominal Grid Voltage is also indicative in PVsyst. However it is used for the evaluation of the AC losses (i.e. for the wire current) when defined. |
| In the reality, the output voltage of the inverter will follow the voltage imposed by the grid at any time. The device is usually equipped with securities which will disconnect when the voltage goes outside a specified voltage range (in Europe -10% / +6%). But the effective Voltage thresholds specification is not part of the PVsyst parameters. By the way, PVsyst has no indication on the real grid voltage at a given time in the simulation process, and could of course not use this information. |
| PNomAC | Nominal AC Power is the crucial parameter of the Inverter definition. It is the power the inverter can feed continuously. In PVsyst, when going over this power the limiting strategy is applied (displacement in the I/V characteristics, or cut). |
| PMaxAC | Maximum AC Power is often specified by the manufacturers, but its signification is not always clear. It is usually a power which may be produced for a short time, until the inverter's temperature becomes too high. Since the version 6.30, PVsyst manages a temperature dependency of the nominal power in operating conditions, and this parameter is involved in the increased available nominal power. |
| INomAC | Nominal AC current is often specified in datasheets. Its value is usually the current under Nominal power and Nominal grid voltage (see Grid current for tri-phased), which you can obtain by clicking the associated Checkbox. Not used in the simulation. |
| IMaxAC | Maximum AC current is also an absolute rating specified by the manufacturer, not used in the simulation of PVsyst. |
See also the inverter model: Input and Output page.
Efficiency
This panel is a remainder of the maximum and EURO (or CEC) efficiencies, as determined by the efficiency curve.
European efficiency, is an averaged efficiency over yearly operating conditions in central Europe.
CEC efficiency is the equivalent for US South-West conditions.
Efficiency defined for 3 voltages: There is the opportunity to define 3 different efficiency curves at different input voltages. At the simulation time, the program will perform a parabolic interpolation between them.
See also the inverter model: Efficiency page.