Shunt and series resistance are important to model a realistic PV module. These resistances demonstrate the non-idealities in a PV module. The series resistance Rs defines the resistance of the material that collects the charge from the PV module. This resistance is small and ideal value is zero. The shunt resistance Rsh defines the defects in the semiconductor and the electron-hole recombination before it reaches the output. The value of this resistance is very high and ideally, it is infinity.
On a current-voltage curve, the shunt resistance lies on a slope near Isc and series resistance on the slope near Voc. To elaborate this further, consider that the series resistance is zero and therefore, the voltage V=Vsh.
On a current-voltage curve, the shunt resistance lies on a slope near Isc and series resistance on the slope near Voc. To elaborate this further, consider that the series resistance is zero and therefore, the voltage V=Vsh.
As the voltage increases the current through the shunt resistance increases and output current decreases until the Voc is reached. This is governed using the equation
I=Ip-(V/Rsh)
The value of Rsh is located near the Isc and Rs is near the Voc and can be calculated as follows
Rsh=1/slope
Rs=1/slope
The slope is based on few samples from the curve. For example, consider three arbitrary values of Voc and corresponding current
0A 51.8V, 1.2A 50V, 1.75A 49 V
Enter these two values in two columns in MS EXCEL and use =SLOPE(G12:G14, H12:H14)
The G12, G14 and H12 and H14 correspond to the cell address where the values are entered. The result for the above mentioned arbitrary value is 0.6299 and hence Rs=1.58 ohm. Similarly, the value of Rsh can be calculated.