Calculating Design Voltage and Current for a PV Array

The design voltage and current for a PV array are essential parameters that must be calculated to ensure the system operates correctly and safely. The IET Code of Practice for Grid Connected Solar Photovoltaic Systems provides guidelines on determining the design voltage and current.

Step 1: Determine the Module Characteristics

Find the open circuit voltage (V_oc) and short circuit current (I_sc) of the PV module. For example:

Step 2: Calculate the Maximum System Voltage and Current

Calculate the maximum system voltage (V_max) and maximum system current (I_max) using the following formulas:

• V_max = V_oc x N
• I_max = I_sc x M

N is the number of modules in a string, and M is the number of strings in parallel. For example:

Step 3: Apply the IEC CoP Correction Factors

Apply the IEC CoP correction factors to the maximum system voltage and current to obtain the design voltage and current:

• Design Voltage = V_max x 1.15
• Design Current = I_max x 1.25

These correction factors account for temperature and other variations that may affect the actual performance of the PV array. For example:

So, for the first example, the design voltage and current are 517.5V and 33.75A, respectively, and for the second example, they are 414V and 40A, respectively.