Step 6 Minimum MPPT Voltage

Concept

VPmax STC Voltage at maximum power of PV module at STC/Maximum power voltage / Voltage at Pmax, VPmax STC/Vmpp/Vmp/Vm (V)

VPmax min Minimum voltage at maximum power of PV module (V)

βVpmax Temperature coefficient for voltage at maximum power (% °C⁻¹ or % K⁻¹). 

• In most cases, if βVpmax is not given, then assume βVpmax = temperature coefficient of Pmax, γPmax.

Tmod max Highest module temperature (°C) 

• Assume 75°C if not given

TSTC Module temperature at STC (°C), 25 °C

6.2 Calculate Ns min mppt

Ns min mppt Minimum number of PV modules in series based on minimum voltage at maximum power (units)

𝜂cable DC cable efficiency (decimal)

• Refer to MS 1837:2018, the highest cable loss is 3%, so assume 100% - 3% = 97% (0.97) if not given

Vmin mppt inv Minimum MPPT input voltage of the inverter (V)

• Maximum power point of the PV array can't be tracked if inverter input voltage less than this value. Surrounding temperature rising cause input voltage drop.

• Select "MPP voltage range for nominal power" for Vmin mppt inv value

Ns min mppt = round down [ 130/(24.575 * 0.97) ] = round down [5.45] = 6 units of PV modules