PV Voc Functions

PV Voc Functions#

When designing the strings for a PV solar system, the string voltage shall never be higher than the input voltage of the inverter or storage controller. PV panels nameplate voltage is typically shown at the standard testing condition (STC) temperature of 25C. As the outside temperature drops, the open-circuit voltage of the panel will increase.

To ensure that this voltage doesn’t over-voltage the connected equipment, we need to use the minimum site temperature, and the \(\beta\) of the panel. We will assume that it is -0.5 unless you pass a different value.

Temp Adjusted Voc#

temp_adj_Voc(Voc, temp, beta=-0.5, STCtemp=25)
Module:

src.jmktools.pvsolar

Parameters:

  • Voc (float) – The open-circuit voltage of the PV Panel

  • temp (float) – The minimum temperature that the panel will be operating.

Returns:

Adjusted Voc in volts

Return type:

float

The Voc of a panel will increase as the temperature decreases. The datasheet Voc is typically at STC, or 25C. As the temperature decreases this Voc needs to be adjusted. This adjustment is linear based on the beta value with the units %/C. This beta value will be shown as a negative indicating that as the temperature increases, then the Voc will decrease. This Voc decrease results in derating of power during temperature above 25C.

Voc = The STC panel open circuit voltage temp = The min or max temperature for the PV plant. beta = The panel temperature coefficient. default -0.5%/C, typical values will range from -0.2 to -0.45.

The adjusted Voc is Voc minus the voltage shift. When the outside temperature is above the STC value then the Vocadj will be lower.

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