UC Irvine

This dissertation explores the feasibility of using resonant converters for maximum power point tracking (MPPT) of solar power. Resonant converters are known for their high efficiency, compact size, low EMI, and high power density. However, one crucial factor of resonant converters hindered their applications in many areas, i.e., lack of full regulation capability. Recently, the fixed on-time modulation method was reported to series resonant converters (SRCs), enabling them with full range regulation. This advantage is adopted in this thesis for maximum power point tracking (MPPT) applications. A precise and responsive perturb and observe algorithm is employed as the MPPT method to achieve maximum power output from the solar system. Chapter 1 provides a comprehensive literature review on MPPT applications with SRCs. It examines the characteristics of PV arrays, explores soft-switching techniques and resonant converters for high-efficiency topologies, and investigates various MPPT techniques to achieve fast and accurate tracking of the maximum power point. Chapter 2 focuses on analyzing the fixed on-time control method for half-bridge SRCs. This analysis enables half-bridge SRCs to perform full-range regulation within a limited frequency range, making them viable candidate for MPPT applications. In Chapter 3, experimental results are presented. A prototype of a half-bridge SRC is built with a nominal input voltage of 36V to utilize with a PV panel. The prototype demonstrates a peak efficiency of 95.4% in a 180W application, validating the high efficiency of the prototype. Moreover, the MPPT experiment is conducted using the half-bridge SRC prototype, demonstrating its ability to track the MPP of the PV array with a deviation of only ±2W from the actual maximum power. The prototype exhibits a good efficiency of 92.6% during this process. Chapter 4 compares the half-bridge SRC with a conventional buck converter, highlighting the differences between their hard-switching and soft-switching characteristics. The results demonstrate that the half-bridge SRC displays efficiency enhancements ranging from 2% to 5%. Chapter 5 presents the conclusions drawn from this study, along with a discussion on the future directions and potential areas for further investigation.