Additional PV Panels on certain time of the day in the string

[scholar2k3]

Dear All,

I hope this message finds you well. I am getting in touch to seek professional advice on optimising my solar system setup. Below are the specifications of my current solar configuration:

• Solax 7.5 G4 Single Phase Inverter
• AIKO Panels: 12 panels in each string
• Solax 12kWh Battery

The 2-string inverter operates at 600V for each string, with a total power capacity of 11000W, accounting for oversizing given the inverter's rating of 7.5kW. Each string consists of 12 PV panels, each panel generating 450W with a short-circuit current of 40.30V. Tigo optimisers are installed on each panel to monitor individual performance throughout the day.

I have identified an opportunity to enhance the system's energy generation by utilising additional flat roof space to accommodate eight more panels. The plan is to integrate four panels into each string during specific periods of the day when solar energy generation is suboptimal. However, it is crucial to automatically disconnect these additional panels from each string when the voltage approaches the 600V limit.

In considering an effective solution for this automation process, I have contemplated the use of a PLC/DPDT relay system. However, I am uncertain about its feasibility and whether there might be pre-existing switching systems designed for this purpose, eliminating the need for an additional inverter.

I would greatly appreciate your professional guidance on the most suitable method to automate the integration and disconnection of the additional panels into/from each string, ensuring optimal performance while adhering to voltage limits.

Thank you in advance for your expertise and valuable insights.

Best regards,
Scholar2k3

 

[Richard-the-Ninth]

Sorry, I don't know what you can use, but you can't use a standard PLC or relay to switch the D.C. from your panels. As it is D.C. the current will try to flow as long as it has a connection, but in so doing it ionises the air, so continues to flow until the gap becomes too far.

You can see an example in this video.

 

[ProDave]

Which is a GOOD demonstration of why you should turn the ac output off first, so the inverter is not drawing any power from the panels, before you open the dc isolator.

 

[binky]

DC needs twice the air gap of AC devices.

 

[Bob Minchin]

Use your plcc to open the ac , then switch the dc and finally reconnect the ac with say a 1 second delay between each step.