Analysis and implementation of soft-switched bidirectional buck-boost DC-DC converter for solar PV–fed LED street lighting systems

Abstract

This paper presents a single-stage solar photovoltaic (SPV) fed light-emitting diode (LED) street lighting system (LED-SLS) using a novel soft-switched buck-boost bidirectional DC-DC converter (BDC). A coupled inductor (CI) based auxiliary circuit is used in the proposed BDC to achieve soft switching, which leads to improved efficiency with reduced ripple. As SPV power is avail able during day time alone, a battery storage system (BSS) is used. The BSS is chargedfromSPVduringdaytimethroughtheproposedCI-BDC.TheBSSpow ers the LED-SLS during night time through the same CI-BDC. The proposed CI-BDC provides various advantages like buck/boost operation in either direc tion of power flow, zero voltage switching (ZVS) soft-switching, use of single magneticcore,highefficiency,reducedrippleinoutputcurrent,andsimplecon trol. Also, it provides an illumination control of the LED-SLS using pulse-width modulation (PWM) dimming. To maintain high efficiency even at light loads, the proposed CI-BDC works as conventional BDC by turning OFF the auxil iary circuit. Thus, avoiding the high conduction losses in it at light loads. The detailed working principle and design analysis are presented along with simula tion results. A prototype of 40 W LED lighting system has been developed, and experimental validation is presented