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.