A Power Smoothing System Based on Supercapacitors for Renewable Distributed Generation

With the increasing share of renewable power sources in distribution networks, a smooth delivery of the power generated has become a relevant requirement for ensuring proper power quality. This paper presents a simple power smoothing strategy based on supercapacitors for power conditioning of distributed renewable generation. The power smoothing controller generates the power reference for the dc/dc converter, which has a power tracking control implemented with sliding-mode techniques. The proposed strategy consists of a voltage controller capable of maintaining the optimal state of charge and reducing high-frequency components of the power coming from renewable energy sources. A generalization of the PI structure is used to ensure simple design and implementation. With the proposed control structure, tuning is reduced to find a state feedback gain based on a pole placement criterion. In addition, a criterion for selecting supercapacitors´ size is provided. The effectiveness of the proposed power smoothing scheme is evaluated by simulations and validated in an experimental platform.