Ramp-Rate Limitation Control of Distributed Renewable Energy Sources via Supercapacitors

The growing penetration of converter-interfaced distributed renewable energy sources (CI-DRES) has posed several challenges into the electric power systems, e.g., the instability caused by the intermittent nature of the primary sources, power quality issues, etc. Several algorithms have been proposed to mitigate the CI-DRES power fluctuations and reduce high active power ramp-rates (RRs) at the point of common coupling (PCC) with the grid using energy storage systems (ESS). However, these algorithms present some drawbacks. In this article, a new ramp-rate limitation (RRL) control method is proposed to address existing gaps in the technical literature. This algorithm is performed considering the connection of a supercapacitor (SC) at the dc-link of a DRES converter. The relationship between the SC voltage and the degree to which the RRL is achieved is established, aiming to reduce the SC voltage fluctuations and increase the SC life time. The RRL control is validated in a real experimental testbed and compared to state-of-the-art approaches. This control is also modeled in Matlab/Simulink in order to perform techno-economic investigations on the influence that several parameters (SC size, SC charging/discharging cycles, cost, etc.) have on the achieved RRL at the DRES PCC.