  The frequency stability of a power system is of paramount importance, as a
fast frequency swings in the system can lead to oscillatory instability, and
thereby blackouts. A grid-connected microgrid, that can operate in the islanded
mode can also possess such deteriorating effect due to the higher share of
converter-based sources. In this paper, a coordinated frequency control within
a distribution network is discussed, with a higher share of Photovoltaics (PV).
The main objective of this paper is to test the grid-forming capabilities of
PVs, without the requirement of an energy storage in the network. The tests
were carried out with the help of the Typhoon Hardware-in-the-loop (HIL)
platform using a real Cypriot network feeder. The real-time results confirm the
efficacy of the PV as a grid-forming inverter, provided it has sufficient input
(irradiance) to provide for the loads within the system of interest. The
grid-forming PV also possesses the capability of reconnection with the utility
grid through a synchronizer switch that requires minimal communication, makes
the overall control independent of any other power source, subject to certain
irradiance and loading conditions.
