IMPROVED HIGH GAIN DC-DC CONVERTERS FOR MICROGRID AND ELECTRIC VEHICLE APPLICATIONS

Abstract

The world-wide energy consumption raised by 34% with associated carbon dioxide gas emissions increased by 15% from 35.7 billion metric tons (bmt) to projected 41 bmt in 2050. These factors of increased energy consumption and CO2 emission have attracted the alternate green energy sources with zero carbon emission regarding environmental protection concerns. The aforementioned micro sources are mostly at consumer premises and can be able to form dc microgrids. The merits of green energy micro sources are zero-emission, highly consistent, low cost and on the other hand major limitation of these sources is the low voltage at their output terminals. In order to comply with the applicability concerns power electronic-based power conditioning is required for these micro sources in terms of the low terminal dc voltage. The amplification can be done by two types of power electronic converters i.e., isolated and nonisolated dc-dc converters. In isolated converters, the voltage transformation ratio depends on the magnetic coupling i.e., with transformer or coupled inductor technologies prime focus being on the turns ratio. These topologies are often in danger if their leakage flux is not properly processed. Moreover, this leakage flux also causes voltage spikes across the switch at the high-voltage side. The aforementioned constraints demand a peculiar design of magnetic components which in turn dictates the cost, density, efficiency, and scalability of the magnetically coupled dc-dc converters. The nonisolated topologies i.e., non-magnetically coupled dc-dc converters are more in demand due to the absence of the aforementioned constraints. These nonisolated converters have inherent features such as simplicity in construction, compactness, efficiency, and low cost concerns. The primitive classic boost converter is a simple solution but it has the adverse effects of drastically decreasing efficiency at extreme duty ratios at which it has to be operated to attain high and or ultra-high voltage gains. The later evaluated versions of boost converters like passive, active, and hybrid switched inductor converters, switched capacitor topologies, and voltage lift-voltage multiplier-based converters have major demerits such as high current stress, elevated component count, and reduced efficiency. Recent elegant interleaved integrated passive-switched-inductor topologies of common grounding with split duty and iii reduction in long conducting intervals for switches are the viable alternate solutions for the aforementioned converters. The interleaved split duty-based converters possess the feature of low duty for the switches but the overall cumulative duty cycle is still high with a relatively high element count and elevated output capacitor inrush currents at the end of each switching cycle. In addition, the overall elevated duty ratios make the efficiency of the converter to be less followed by the heating concerns. This typical concern demands the evolution of dc-dc converters consisting of high boosting factors at low duty ratios, such analogous featured converters are quadratic boost dc-dc converters. This converter features a high boost factor at a low duty which in turn lowers the voltage and current stresses, and improves the efficiency. Here much attention is required for the design of the second inductor because of its high voltage excitation and high sizing requirements. The feature of high boost factor at low duty especially at lowered upper bound limit is also possible with impedance (L-C) network-based Z-Source converters that are highly volatile by having discontinuous input currents, this makes them less adoptable for majority applications. To overcome this demerit an analogous converter featuring similar voltage gain and more importantly, a series inductor at the input terminals is reported namely by a Quasi Z Source dc-dc converter, nevertheless because of the low charging interval for the inductors due to their limited upper bound on duty cycle makes the inductors to be bulky and henceforth associated packaging concerns, economical and spacing concerns will persist. In this regard, a single switched inductor modified Sheppard Taylor-based converter is proposed which surpasses the high inductor size and packaging concerns. The recent evolution of dc-dc converters is also abundantly emphasizing the bidirectional dc-dc converters (BDC) for hybrid energy source-based electric vehicle propulsion systems. Among the plethora of BDC’s quadratic boost-buck converters are popular because of their paramount amplification and attenuation consisting of a wide range of duty ratio flexibility, featuring simple topological synthesis and economical concerns towards the stated applications.