Supercapacitor Assisted Hybrid DC-DC Converter for Applications Powered by Renewable Energy Sources

The unstable and unreliable nature of renewable energy sources such as solar, wind and sea waves, could make them inoperable within next few years as a primary energy source in industry applications although they are not causing any critical environmental problems. Storing energy for temporary basis in batteries is not an effective solution for applications demanding instant high current. Batteries due to their limited cycle and calendar life as well as disposal issues make them less attractive in many renewable applications. Introducing supercapacitors as short term energy storage devices is a viable solution to overcome the above problems. Supercapacitor (SC) assisted low drop-out regulator (SCALDO) is a very low frequency DC-DC converter technique, with high end-to-end efficiency, where the load receives a high slew rate capable low noise output of a linear regulator. In this hybrid DC-DC converter, a switched-mode SC assisted input stage reduces the overall switch count of SCALDO and this helps to reduce switching losses at very high input to output voltage ratios. A series supercapacitor is introduced in the input loop with the transformer providing isolation and SC acts as an electronic shock absorber. Series SC is also acting as short term DC-UPS for the power converter. This paper provides an overview of this novel hybrid power converter, discusses control strategy in detail. Experimental results and simulation outcomes are presented to prove the technical feasibility of the concept.