Implementation of Bi-Directional DC-DC Converter for PV Energy System

DC-DC Converters (DDC) are trending day by day as they are most suitable device for interfacing PV. Also, they find wide range of applications in DC based energy appliances as well as power electronic conversion scenarios. The basic functionality of DDC is to transform the DC voltage into another level, may be boost it or buck it. There are numerous topologies available in literature which is meant to accomplish the above mentioned purpose individually or simultaneously. In this work a High Frequency (HF) DDC is presented with lowest component count and low voltage stress to be implemented for solar interfacing. The dynamic behaviour of the proposed topology is analysed for charging and discharging of the DC-battery as a loading conditions. At the end efficiency analysis is also presented in terms of energy loss in the power switches used. The topology is designed with only two switch count which also reduces the component cost of the DDC.

I. Introduction

The electronic circuitry dedicatedly designed to transform the DC-voltage of one level to the another with reduced losses is DC-DC Converters (DDC). Apart from conventional topologies like buck converter, boost; buck-boost converter, flyback and froward converters; there are numerous other topologies designed by the researcher to harbour the best out of DC-DC conversion system [1]. DDC has a wide range of classification depending upon several factors as the type of input and output (buck/boost and both, flyback, CUK), the number of phases (single/multi-phase), the mode of operation (continuous and discontinuous), the switching frequency (low, high and medium), and the topology used (Forward, Push-pull, Half-bridge, Full-bridge, Resonant and Quasi-resonant converters). Also, they are classified as isolated and non-isolated type [2]. In isolated type structure, a transformer is used to change the level of voltage at the output terminal and also it isolates the input and output structure which can also provide the least magnetic interfacing. In this type of topology, the high voltage gain can be obtained by adjusting the conversion ratio of the transformer windings. This topology indeed is beneficial but transformer adds to the additional electrical burden the system as well as it increases the losses in the system. The another is the non-isolated type topology [3], [4]. In this type of topology, the input-output circuit of the DDC is electrically connected. And the voltage conversion between the input and output level is obtained by designing the proper switching of the semiconductor switches connected in DDC as well as by tuning the input and output side lumped parameters. The advantages of the latter topology are it can be easily designed for High Frequency switching applications and also since it has low component count, the losses are reduced hence efficiency is high [5]. Moreover, it also has low voltage stress across the switches. Both isolated and non-isolated structures can be of buck and boost type. Other than these, the widely adopted DC-converters in industrial application is also designed as per the requirement with different topologies.