During islanded operation of microgrid, intermittent renewable energy resources are used as power source. This power is fed into the inverters for AC Microgrid. During variation in power of any intermittent source the input supply to inverter will also vary. What will be the effect of this input power variation to the output of the inverter in terms of its frequency.
Hi Fawad,
Technically, the frequency can be kept unaffected by input power, since it is totally decided by the device switching instances.
However, depending on the nature of the island side and network side performance, and the required way the two should be made to perform, one may wish to relate the frequency to input power by design ! It may be decided to some extent by the behaviour of the renewable power source as well.
Fundamentally however, the two can be kept independent if so required.
-Sanjay
Sir, you mean, for instance, if the power from solar energy is reduced to 300kW from 500kW will this not affect the frequency output of the inverter at the time when power is reducing 200kW?
Not necessarily, Fawad.
The frequency can be varied independently. However, generally a droop control (similar to conventional generators) is employed by design simply to make the renewable unit compatible to the overall grid. But as I said, it is by design, not due to any implicit feature of the inverter. Similarly, other frequency variation logic too, may be employed by design.
With best wishes.
-Sanjay
Sir, Thank-you so much for your answers! now what i understand is actually all RE generator characteristics (Frequency/Voltage droop %) are kept constant to share power equally between them. However a change in power in RE generators may cause instability in a complete grid system in terms of frequency and voltage if they are not pre-settled in case of inverter interfaced RE Generators and that setting is actually droop control.
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