GunnsElectPvArrayV2 - nasa/gunns GitHub Wiki

This is a variant of GunnsElectPvArray with a new & improved version 2 photovoltaic string/cell model (GunnsElectPvString2). This model has a few improvements over the baseline (GunnsElectPvArray with the original GunnsElectPvString):

• This avoids the efficiency problem present in the baseline GunnsElectPvArray, documented in Issue #90. This version 2 implements the cell efficiency correctly. Whereas the old model uses efficiency as an input (incorrectly), this new model calculates the efficiency and fill factor as an output resulting from the other given configuration data.
• This allows for specification of equivalent cell diode ideality, whereas the baseline version does not.
• This models a more realistic performance curve of the cell, whereas the baseline model uses a linearization about the maximum power point. This will give more realistic string currents at a given regulated voltage, and more realistic number of shunted strings by a shunting regulator.

This version has a few important limitations relative to the baseline version. See the Limitations section below.

For new projects, we recommend using this new V2 array shape if possible, given the above limitations. We’ve kept the old shape for backwards-compatibility.

This link is connected and used the same way as GunnsElectPvArray.

Same as GunnsElectPvArray.

Same as GunnsElectPvArray.

Note that some of these parameters, such as Voc, Isc, Vmp, Imp, Reference T, etc. are likely to be found on the vendor’s data sheet for real-world solar cells & arrays.

• cellRefVoc: same as cellOpenCircuitVoltage from GunnsElectPvArray.
• cellRefIsc: same as cellShortCircuitCurent from GunnsElectPvArray.
• cellRefVmp (default = 0 (V), must be between DBL_EPSILON and cellRefVoc): This is the reference cell’s voltage at its Maximum Power Point at reference conditions.
• cellRefImp (default = 0 (V), must be between DBL_EPSILON and cellRefIsc): This is the reference cell’s current at its Maximum Power Point at reference conditions.
• cellRefTemperature: same as GunnsElectPvArray.
• cellRefCoeffDVocDT: same as cellTemperatureVoltageCoeff from GunnsElectPvArray.
• cellRefCoeffDIscDT: same as cellTemperatureCurrentCoeff from GunnsElectPvArray.
• cellIdeality (default = 0, must be between 1.0 and 1.5): This is the ideality constant of the diode in the single-diode equivalent circuit model. Normally a value of 1.0 can be assumed, but real cells typically have values between 1 and 1.5. Note that higher values towards 1.5 make it more likely that the model will fail to initialize. See the limitations detailed below.
• cellArea (default = 0 (m2)): This is the surface area of one side of the reference cell. This is an optional field; it is only used in the output efficiency and fill factor calculations. This can be left zero, causing the model to omit calculating efficiency and fill factor.
• sectionSourceAngleExponent: same as GunnsElectPvArray.
• sectionBacksideReduction: same as GunnsElectPvArray.
• sectionSourceAngleEdgeOn: same as GunnsElectPvArray.
• sectionRefSourceFluxMagnitude: same as GunnsElectPvArray.
• stringBlockingDiodeVoltageDrop: same as GunnsElectPvArray.
• stringBypassDiodeVoltageDrop: same as GunnsElectPvArray.
• stringBypassDiodeInterval: same as GunnsElectPvArray.
• stringNumCells: same as GunnsElectPvArray.
• *arrayNumSections: same as GunnsElectPvArray.
• *arrayNumStrings: same as GunnsElectPvArray.

All input data is identical to GunnsElectPvArray.

• Link thows initialization errors: As described above, the model can’t handle all combinations of configuration data parameters, including some combinations that might represent real-world cells. Based on the given configuration data, the model may calculate the remaining parameters of the equivalent cell model, such as shunt or series resistances, to be negative numbers, which would be invalid. To help avoid these situations, we have provided a tuning helper spreadsheet in the GUNNS repository at: aspects/electrical/SolarArray/GUNNS_PV_Array_Tuning_Helper_V2.xlsx. You can use this spreadsheet to predict how the runtime model will perform, given a set of configuration data and input temperature and lighting conditions.

• N/A

• This version of the Array is not compatible with and should not be used with the GunnsElectPvRegConv downstream regulator. It is really intended for use with the GunnsElectPvRegShunt regulator, or a future Maximum Power Point Tracking (MPPT) regulator.
• This version may cause the network to take more CPU time to solve, due to the larger amount of math it computes for the higher-fidelity performance curve. We have not quantified this increase.
• Some combinations of reference cell parameters result in invalid solutions, and can’t be modeled. Such conditions will be indicated as an initialization error reported to the Health & Status log from the link during network initialization This may prevent this model from working for some normal, real-world cell types.