Multiple harmonic analysis and electromagnetoquasistatic modeling for high frequency resonant converters with simulation-driven design optimization

Abstract

Emerging applications in power electronics create new opportunities and challenges for resonant converters. Advanced analytical methods and systematic design approaches are needed due to the high switching frequency and diverse resonant topologies. This thesis explores new techniques to analyze, design, and optimize the resonant converter circuits along with their self-resonant components. First, an analytical technique called multiple harmonic analysis (MHA) is developed to directly capture the steady-state electrical quantities and waveforms in the resonant converters. MHA is applicable to various resonant topologies as the Fourier-series approach is used to represent the generalized building blocks of resonant converters. From the experimental measurements, it is verified that MHA provides more accurate results and more effective circuit designs than the conventional fundamental harmonic analysis method. Next, an emerging wireless power transfer (WPT) converter using coil resonators in domino form, referred to as the domino-resonator WPT system, is investigated. The converter is used as a wireless power supply that delivers power to the online monitoring equipment mounted on the high-voltage transmission tower. The converter’s key component is a series of self-resonant coils on printed circuit boards (PCBs), embedded in the sheds of an insulator string. An electromagnetoquasistatic model is built to explore the inductances and parasitic capacitances of the PCB coil resonators. Self-resonant frequencies and unequal current distributions are predicted. The loss mechanism of the PCB coils is then studied, followed by a simulation-driven design optimization framework to automate the coil design process. Practical measurements show that the optimal design improves the quality factor (Q factor) from 52 to 132 as compared to the existing trial-and-error design. The efficiency of the corresponding WPT in a 20 W prototype across a 1.14 m distance improves significantly from 11% to 46%. Finally, a systematic design method is developed to address the issue of voltage regulation and efficiency optimization in domino-resonator WPT converters. A complete WPT converter is built following the proposed design approach. Nearly load-independent constant output and zero phase angle are observed in the measurements, confirming the effectiveness of the design method.