I'm reading about integrating PV into legacy grids, and I saw the following scheme:

enter image description here

Left side is middle voltage grid, and right side is low voltage grid (400V AC). It is talking about communication between PVs about stabling the inductive power, but if both feed in with the same frequency and in-phase, what communication do they need to have? What could be the problems in such a configuration?

This image is taken from "Aufnahmefähigkeit von Niederspannungsverteilnetzen für die Einspeisung aus Photovoltaikkleinanlagen" by Georg Kerber

  • \$\begingroup\$ What is the translation of x and y axis? \$\endgroup\$
    – Hazem
    Commented Feb 10, 2018 at 15:35
  • \$\begingroup\$ y: Grid Voltage x: Conducting length (cable length) \$\endgroup\$
    – EralpB
    Commented Feb 10, 2018 at 18:25

1 Answer 1


The problem you are facing here is the individual PV inverters are having a different idea of what the AC power flow is. They only see voltage and the phase angle between voltage and current at their own location.

If the grid is reasonably soft, as most low voltage grids are, turning on/off a big inductive/capacitive consumer can make the local grid "bounce" and cause "ringing" between the regulation circuits of multiple PV inverters. This is especially bad with washing machines and microwave ovens, which are controlled in an off/on fashion.


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