Electrical – Identify when the inverter is pumping energy back into the grid


Assume I have access to my solar panel inverter's voltage, current, and reactive power measurements, and these are taken every 5 minutes.

  1. By inspecting this trace, how can I tell when my panel is feeding
    energy back to the grid? Is there any other information I need to
  2. Can I also calculate how much energy is being pumped into the
    grid? (Even a rough estimate will suffice.)

I do not have a background in power engineering, so I'd appreciate any responses that assume minimal knowledge of the domain. Thank you!

Best Answer

If you only know the inverter's voltage and current, then you can't deduce whether it's feeding power to the grid, or drawing power. For this, you need their relative phase. When they're in phase, the power flow is one way, in the opposite phase and the power flows the other way.

An inverter that's designed for grid tie injection will usually have a facility to read power flow. A metering system designed to allow you to claim payment for the power will always be able to read power flow.

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