Date of Award

29-5-2024

Document Type

Thesis

School

School of Electrical & Electroncis Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.N.Prabaharan

Keywords

High Gain Converter, Quadratic Boost Converter, Reliability, Photovoltaic System, Maximum Power Point Tracking

Abstract

Fossil fuel-based power plants emit 25% of greenhouse gases and 40% of carbon emissions globally. Therefore, several countries focus on deploying RES-based electricity production (such as solar and wind). As per the International Energy Agency report, solar PV might be the lowest-cost option for generating electricity in the future. Solar energy is highly emission-free, but it is still a key challenge in procuring the maximum amount of energy from solar PV due to its non–linear characteristics. Therefore, a DC-DC converter must integrate with solar PV to increase the output voltage level. Many existing topologies exist in the literature, but the utilization of device count or operating duty cycle is higher to attain the required voltage gain.

So, emerging topologies are still required to improve performance parameters based on different applications. Therefore, the main objective of this research work is to design a high-gain quadratic-based DC-DC power converter for solar PV applications. The first specific aim of the research objective focuses on the design of a novel nonisolated high gain quadratic-based DC-DC converter topology. Three different proposed converters are designed focusing on the improvement in size, voltage gain, number of components, voltage stress, etc. The first proposed converter (P-I) combines a novel voltage multiplier unit (VMC) (4C, 2L, 2D) with a modified quadratic boost converter to attain a voltage gain of 10.75 at a 60% duty cycle.

Although the converter attains higher voltage gain, the total component count (TCC-20) is higher. So, a proposed converter-II (P-II) is developed to focus on reducing the components, thereby increasing power density. It utilizes 16 components to attain a voltage gain of 9.75 at a 60% duty cycle, providing an efficiency of 91% with a power density of 1.03 kW/L. Even though the proposed converter has improved power density and voltage gain, the efficiency of the converter is lower. Therefore, an attempt is made to design a proposed converter-III (P-III) focusing on improving the efficiency and power density with less TCC. The proposed converter-III can provide 93% efficiency by utilizing 12 components with a power density of 1.36 kW/L. The operation of the proposed converters is validated through the laboratory-based experimental prototype.

The second specific aim of the research objectives focuses on the stability and reliability analysis of the proposed converter-III. The stability analysis is performed for the proposed converter-III using a PID controller in closed-loop conditions. The validation of the PID closed-loop controller is verified using MATLAB-Simulink with a wide range of variations in the different parameters, such as input voltage, load value, and reference voltage values. The simulated results show that the proposed converter with a PID controller adapts well to dynamic changes. Reliability analysis is performed using the military handbook (MILHDBK- 217F) to predict the failure rate of individual components in the proposed converter- III. It is found that the failure rate of the switch is higher than that of any other component in the proposed converter-III.

The third specific aim of the research objectives focuses on the integration of the proposed converter-III with solar PV for procuring maximum power. The whale optimization algorithm effectively finds global peaks under partial shading conditions, but the exploration process of theWOA is lacking due to the randomness of the initial search process. Therefore, a modified whale optimization algorithm (MWOA) is proposed to identify the initial search process to reduce the exploration time. It would reduce the convergence time by providing an optimized duty cycle under varying irradiation conditions. The system is examined with three different patterns in MATLAB Simulink Environment such as pattern 1 (1000W/m2), pattern 2 (1000W/m2 and 600W/m2) and pattern 3 (1000W/m2,600W/m2 and 800W/m2). The simulated results show that the MWOA performs well with the proposed converter-III during the partial shading conditions.

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