Comparative Evaluation of Ramp-Rate Limitation Control Strategies Employing Supercapacitors

The advent of Converter-Interfaced Distributed Renewable Energy Sources (CI-DRES) has posed several challenges within electric power systems jeopardizing its robustness and stability. On the bright side, the increased controllability of the Voltage Source Converters used as an interface of the CI-DRES with the grid together with the use of fast-acting Energy Storage Systems- such as Supercapacitors (SCs)- enable the CI-DRES to provide Ancillary Services (AS) to the grids. Since the majority of CI-DRES depends on a primary source with intermittent characteristics (wind, solar irradiance, etc.), a possible AS is the Ramp-Rate Limitation (RRL) of the active power of the CI-DRES primary source. This action is also referred as power smoothing. Several control strategies have been proposed in the technical literature, each of them having different advantages or drawbacks. This paper presents a parametric evaluation of the power smoothing control strategies which employ a SC. The parameters analyzed are the involved purchase cost, the measurement time window of the smart meters used within the electric power systems and the finally achieved RRL.