Bidirectional dc to dc converter is used as a key device for interfacing the storage devices between source and load in renewable energy system for continuous flow of power because the output of the renewable energy system fluctuates due to change in weather conditions. In electric vehicles also, bidirectional converter is used between energy source and motor for power supply from battery to motor. Thus, bidirectional dc to dc converters are getting more and more attention in academic research and in industrial applications. Bidirectional dc to dc converters work in both buck and boost mode and can manage the flow of power in both the direction between two dc sources and load by using specific switching scheme and phase shifted control strategy and hence generated excess energy can be stored in batteries/super capacitors. Therefore, the basic knowledge and classification of bidirectional dc to dc converters on the basis of galvanic isolation, the comparison between their voltage conversion ratio and output current ripple along with various topologies researched in recent years are presented in this paper. Finally, zero current and zero voltage soft switching schemes and phase shifted controlling techniques are also highlighted.

The demand of quality power is increasing continuously. The problem of global warming and rate of decrease of non-renewable energy sources are increasing day by day. Hence renewable energy sources such as fuel cell, solar, Magneto hydro Dynamic (MHD), geothermal are the best alternatives to solve the problem of environmental issue and increasing demand of energy.  The output of these resources is dc, therefore to connect these resources to the grid, multilevel inverter is the key device. But the output of multilevel inverter has power quality issues such as harmonic generation and notching due to conversion of dc to ac and high number of switch. Hence, this paper deals with harmonic elimination using Genetic Algorithm based Selective Harmonic Elimination (GA-SHE) techniques for asymmetric and symmetric topology of MLI. In the present study, comparative study among the 5-level, 7-level, 9-level, 11-level and 15-level multilevel inverters with reduced number of switches topologies has been discussed. A novel topology of 15-level inverter which consists least number of switches has been designed for a desired voltage level. Also, the comparison of Total harmonic distortion developed in the output voltage generated by different topology at different levels with the proposed 15-level inverter topology are discussed.

In the recent years the use of commercial sources like coal, diesel, nuclear etc have been increased. In the coming years the conventional sources may evanesce. So, now the prime concern of the engineers and researchers are shifted towards the non-conventional sources such as solar plants, fuel cells, batteries, wind power etc. But the problem in most of these sources is deliver very low and unstable voltage and such sources are not good for commercial use. So, to utilize these non-conventional sources it is required to tie the supply to grid. dc-dc converters are widely used in PV applications. Many researchers presented advancements in dc-dc converter topologies in literature. This paper presents the wide review on recent topologies of dc-dc converters.Index Terms-High gain dc-dc boost converter; high voltage gain; interleaved boost converter; magnetic coupling; switched inductor; multi-level; multistage; switched capacitor; voltage multiplier cell.

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