MODELING, DESIGN, AND IMPLEMENTATION OF HIGH GAIN POWER ELECTRONIC DC-DC CONVERTERS FOR NANOGRID APPLICATIONS

Abstract

Nanogrids are nothing but power distribution systems that are based on renewable energy sources and are apt for low-power home applications. Nanogrids are considered to be the building cells of a Microgrid. Nanogrid is intended for feeding domestic loads (of the order of 100 W to 5 kW) from renewable energy sources such as wind farms, roof-top solar photovoltaic, biomass, and fuel cell, etc. Nonetheless, the voltages produced by these renewable energy sources are small and not sufficient enough to be utilized in all the applications. Hence, it is necessary to include high gain and high-efficiency DC-DC converters in the system. To interface the generators and the loads, power electronic converters are employed within a Nanogrid. The power system grid is also linked to the Nanogrid using these converters. The most fundamental characteristics of the high-gain DC-DC converters are high efficiency, high-voltage gain, and low voltage/current stress on switching components. A comprehensive literature review of various boosting methods is disseminated in this research work. After a detailed investigation, five new DC-DC power converter topologies have been designed and developed to achieve high gain factors with reduced switch ratings and low cost for use in Nanogrids. The proposed converters cannot only reduce voltage/current stresses across the switching components significantly but also achieve a higher voltage gain at moderate duty cycles with a lesser number of components. Moreover, the proposed converters are designed in such a way that they can maintain a continuous input current, and hence making them useful for power conversion in the battery, fuel cell, and solar PV applications. By using boosting technique five novel high voltage gain DC-DC converters are developed and presented in the dissertation, namely: 1. modified Switched Inductor Boost Converter (mSIBC) with reduced switch voltage stress, 2. Transformer-less Boost Converter (TBC) with reduced voltage stress, 3. Switched-Inductor based DC-DC Converter with reduced switch current stress, 4. Novel High Gain Active Switched Network-Based Converter, and 5. Double Stage Converter with low current stress for Nanogrid The detailed theoretical analysis of the voltage conversion ratio, parameter design, continuous and discontinuous conduction mode, and advantages are presented. In addition, a detailed comparative study of each converter topology is also given. The functionality of the proposed power converters is tested in real-time by developing Laboratory prototypes of the proposed converters and the theoretical analysis is validated by obtaining the experimental results. The proposed converter configurations are simulated in MATLAB as well, to verify the theoretical analysis. Simulation results of all the proposed converters are presented indicating clear evidence of the expected predictions in close proximity with experimental results.