Configuring a Solar Array

Configuring a solar array for an inverter involves ensuring that the solar panel array's voltage and current characteristics align with the inverter's/charge controller’s specifications, including maximum voltage input, minimum voltage input, MPPT (Maximum Power Point Tracking) operating range, maximum current input, and maximum wattage input. 

Here's a step-by-step guide:

Review Inverter Specifications: Gather information on your inverter's/charge controller’s specifications, including: 

• Maximum Voltage Input (VOC): The highest voltage the inverter/charge controller can handle. This is calculated using open voltage (VOC) 
• Minimum Voltage Input (VMP): The lowest voltage at which the inverter/charge controller can operate. This is calculated using operating voltage (VMP) 
• MPPT Operating Range (VMP): The voltage range within which the Maximum Power Point Tracking operates optimally. This is calculated using operating voltage (VMP) 
• Maximum Current Input: The maximum current the inverter/charge controller can handle. Depending on the equipment this value can be ISC, IMP, or both amp ratings. 
• Maximum Wattage: The maximum wattage the invert/charge controller can handle.  
• The values above are typically on a per MPPT PV input basis. Inverters typically have 1-4 MPPT PV inputs while charge controllers typically have 1 MPPT PV input. Take this into account when calculating the value below. 

• Example: An inverter has two MPPT inputs. It has a maximum VOC input of 600V. This means that each MPPT input can handle up to 600V VOC adjusted for operating conditions.

Determine Solar Array Voltage:

• Calculate the total voltage of your solar array based on the number and configuration of solar panels. Consider whether the array will be connected in series, parallel, or a combination.

 Check MPPT Operating Range:

• Ensure that the calculated solar array voltage falls within the MPPT operating range of the inverter. This is crucial for optimizing the power output from the solar panels.

Consider Temperature Effects:

• Account for temperature variations, as they can affect the voltage of the solar panels.  
• Solar panel voltages rise when panels get cold and lower when panels get warm. 
• Check the temperature coefficient of your solar panels and adjust, if necessary. 
• The Open-Circuit Voltage (Voc) of a solar array can be calculated by adjusting the standard test condition (STC) VOC value for the actual operating temperature using the temperature coefficient. The temperature coefficient is a parameter provided by the solar panel manufacturer, and it indicates how much the voltage changes with temperature. 
• The formula to calculate the adjusted Voc is as follows: voc_adjusted=voc_STC+(Toperating−TSTC)×(Temperature Coefficient) 

• Voc_adjusted is the adjusted open-circuit voltage. 
• Voc_STC is the open-circuit voltage at standard test conditions (STC). 
• Toperating​ is the actual operating temperature of the solar panels in degrees Celsius. 
• TSTC is the temperature at standard test conditions (usually 25°C). temperature Coefficient is the temperature coefficient provided by the solar panel manufacturer (usually in %/°C). 
• To adjust for operating temperature, substitute VMP in the values above. 
• See below for a step-by-step guide on how to use the formula above.

• Calculate the total current of your solar array based on the number and configuration of solar panels. Do this for both ISC and IMP amp ratings.  

• Ensure that the calculated solar array current does not exceed the maximum current input specification of the inverter/charge controller.  

• Calculate the total wattage of your solar array based on the number and wattage of solar panels. 

• Ensure that the calculated total wattage of the array does not exceed the maximum wattage input specification of the inverter or charge controller.  

• If the voltage is too high, consider reconfiguring the solar panels (e.g., in parallel instead of series) to bring the voltage within the acceptable range. 
• If the current is too high, consider reconfiguring the solar panels (e.g., in series instead of parallel) to reduce the current. 

• Implement a monitoring system to keep track of the performance of your solar array. 
• Regularly check the system to ensure that it is operating within the specified voltage and current parameters. 

• Account for factors like shading, dust, and other environmental conditions that may affect the performance of individual solar panels. 

• If you are unsure about the optimal configuration, consult with a professional solar installer or engineer. 

Important Notes: 

Ensure that the solar panels used in the array are compatible with each other in terms of voltage and current characteristics. 

Follow local electrical codes and regulations. 

By carefully configuring the solar array to match the inverter specifications, you can maximize the efficiency and longevity of your solar power system. Always refer to the documentation provided by the inverter and solar panel manufacturers for specific details and guidelines. 

Here's a step-by-step guide for determining adjusted VOC by temperature: 

• Get Standard Test Condition (STC) Voc: This information is usually provided by the solar panel manufacturer and is the Voc at a specific set of conditions, often 25°C. 
• Get the Temperature Coefficient: Refer to the solar panel datasheet to find the temperature coefficient, typically expressed in percentage change per degree Celsius (%/°C). 
  
• Determine the typical highest and lowest temperature your panels will be operating in. 
  Use the lowest temperature when calculating for adjusted VOC and use the highest temperature when calculating for adjusted VMP. 

• Apply the Formula: 

  Plug the values into the formula mentioned above to calculate the adjusted Voc. 

  vOC_adjusted=vOC_STC+(Toperating−TSTC)×(Temperature Coefficient) 

  vMP_adjusted=VMP_STC+(Toperating−TSTC)×(Temperature Coefficient) 

  The adjusted Voc represents the open-circuit voltage of the solar array under the current operating temperature. Keep in mind that this calculation provides an estimate, and actual operating conditions may vary. Monitoring the system's performance under different temperatures and adjusting the calculations accordingly will help ensure accuracy.