Comparitive Analysis of Frequency Support Provided by Grid-Forming and Grid-Following PVs

Widespread Photovoltaics (PVs), which are seen by
a distribution network (or an isolated microgrid) as a constant
power injecting source, can be detrimental to the frequency
stability of the network. To assist in frequency regulation and
response, the constant current control for a Distributed Energy
Resource is substantially modified to provide inertial response
within the low voltage network. PVs that deploy inertial control
require an additional storage in order to cater to the demand
supply balance. This approach is feasible for large scale PVs,
however, rooftop PVs possess limited flexibility for additional
storage. This paper studies case of a low-voltage networked
microgrid with an appreciable PV penetration, in the presence of
a diesel generator (DG) as a separate bus. A coordinated control
for PV is designed in this paper, which can help in the transition
in between the grid-forming mode to the grid-following modes
(with the inertial control loop acting as the Phase locked loop),
with the help of an auxiliary DC link voltage based control which
is designed in a way that does not require any switching action.