Energy Management In Converter-Interfaced Renewable Energy Sources Through Ultracapacitors For Provision Of Ancillary Services

The ever-growing penetration of Converter-
Interfaced Distributed Renewable Energy Sources (CI-DRES)
and the gradual decommission of synchronous generators
(SGs) has posed several challenges related to the stability
and robustness of the electric power systems. Since the main
interface of the CI-DRES with the grid are the Voltage Source
Converters (VSCs), there has been a major shift in the VSC
control philosophy, where the absence of SGs is compensated by
the Ancillary Services (ASs) provided by a new generation of
CI-DRES. In order to make these ASs feasible and emulate the
dynamic behaviour of a SG, the presence and advanced control
of energy storage systems (ESS) together with the CI-DRES is
essential, so that the CI-DRES/ESS has a dynamic behaviour
similar to SG. In this paper, a new energy management control
system is proposed for an ultracapacitor (UC) connected to
the DC-bus of a CI-DRES. The aim is to control the DC bus
voltage using the UC and, simultaneously, maintain the UC
voltage within the limits while a given AS is provided. The
control strategy is validated experimentally using a prototype
with results revealing a reliable and stable operation.