I’m trying to understand the physics behind AC load distribution when distributed on-site generation is installed and the load is also connected to the grid.

In the diagram below, I have a building that has a PV Array installed and it is also connected the utility.

Building with Solar Gen and Grid Utility Connection

There a number of hypothetical scenarios that could occur:

1) “Building Load 1” draws 100 kW of power and the PV array is generating 100 kW of power therefore the grid utility is not being used to power the building load.

2) “Building Load 1” draws 150 kW of power and the PV array is generating 100 kW of power therefore the grid is providing the 50 kW

3) “Building Load 1” draws 50 kW of power and the PV array is generating 100 kW of power therefore 50 kW of power is being fed back into the utility.

Are those scenarios correct? If so can someone please explain how this works and also the physics behind this?

Given the “Building Meter” position it will monitor the utilisation of the grid and how much energy the PV array puts back into the grid if the building load is less than the solar generation, but how does this occur? How is the power distributed and how does the net value at “Building Meter” measure this? Lastly, how is this being regulated?

I’d be interested in a high-level explanation as well as a more advanced explanation to help me join the dots.

Thank you in advance.

  • 1
    \$\begingroup\$ Current follows the path of lower incremental resistance. By phase shift and amplitude, a GTI can be lower than grid or just lag phase it thus contribute only to the load. Conversely to the grid. Generators are negative impedance. Loads are positive. GTI's supply PF=1 and low harmonics with negative feedback to a PLL sine reference. Thus current direction amplitude and phase are critical to Grid tied Inverters (GTI) with complex controls. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 6 at 19:22
  • \$\begingroup\$ What should I be looking for online for examples and explanations of this? Thank you for the reply! \$\endgroup\$ – Inquisitive Oct 6 at 19:25
  • \$\begingroup\$ vbn.aau.dk/ws/portalfiles/portal/212730460/… Search Power sharing grid \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 6 at 19:34
  • \$\begingroup\$ For pure energy storage systems (no PV) are GTIs also used? \$\endgroup\$ – Inquisitive Oct 6 at 19:37
  • \$\begingroup\$ GTI's are DC to AC only or AC to DC to AC \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 6 at 19:40

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