High Gain Non-isolated DC-DC Converter Topologies for Energy Conversion Systems

Abstract

For the accurate conversion and conditioning of energy in low voltage level applications powered by photovoltaics, batteries, and fuel cells, static power converters are required. This is necessary in order to satisfy the standards that have been set forth by the load system. Applications such as grid-connected inverters, uninterruptible power supply (UPS), and electric vehicles (EV) are examples of uses that place a premium on the efficiency and static gain of a power converter. In theory, the most fundamental nonisolated topologies for voltage step-up are the regular boost and buck-boost converters. Buck-boost converters are sometimes known as dual boost converters. Combining the functions of boost converters and buck converters results in the creation of buckboost converters. In order for these converters to achieve high voltage gain, they usually need to operate at extremely high duty ratios. During this time, the converters suffer large power losses due to the output diode's capacity to execute reverse recovery. Within the scope of this thesis are discussions of novel high stepup topologies with coupled inductors and voltage gain extension cells. In addition, the study of these topologies, together with the design challenges and methodology that were used to develop them, is described here. It is feasible to achieve a large improvement in performance by contrasting the first solution that was provided with the most recent state ofthe-art topologies that were presented. We propose two different topologies, each of which makes use of connected inductors in addition to voltage gain extension cells. Both of these topologies are presented below. Clamp circuits are frequently required for power converters that use linked inductors as a method for managing the switch voltage excursion. Clamp circuits help prevent the switch voltage from going outside of its normal range. To begin, it is suggested that a step-up converter be selected that is basic, has a cheap cost, and is capable of active as well as passive clamping. Comparisons of the performances of the two different kinds of clamp circuits reveal that the active clamp solution is capable of achieving a greater degree of efficiency than the passive clamp solution. According to the information that is supplied in point two, the most significant downside of increasing the power level of a linked inductorbased converter is the enormous current ripple that is created by the operation of the connected inductor. DCDC converters are often spaced apart in a manner that allows for a variety of distances between them. This allows for the input current to be dispersed uniformly, for the current ripple to be reduced, and for the power density to be raised. This thesis presents a high static gain input parallel output series converter that combines linked inductors, switches the power flow equations, and switches the direction of the power flow. All of these vi

functions are accomplished by switching the direction of the power flow. A closed loop controller that was developed with the assistance of dynamic analysis can be used in order to regulate the output voltage of an interleaved converter. This can be done in a number of different ways. The modelling and experimental data from the high step-up converter designs of the lab prototypes are presented here along with a description of the design process. the results of tests carried out on prototypes of a converter with a single phase output of 250 W and an interleaved output of 500 W;