Technologies for Efficient Wide Voltage Gain Variation in DC-DC and AC-DC Resonant Converters

Abstract

This thesis focuses on developing advanced, high-efficiency DC-DC and AC-DC power converters for applications that require a wide range of voltage adjustments, such as data centers and electric vehicles (EVs). It introduces new designs, methods, and control strategies that overcome the limitations of traditional power converters and offers significant improvements for industries like telecommunications and automotive. The main contributions include a new interleaved LCLC resonant converter, which ensures precise sharing of electrical current across different input voltages. This is achieved through a detailed analysis of how small variations in components affect performance. Another innovation is a novel resonant tank design for a two-phase LLC converter, specifically for auxiliary power modules (APMs), which simplifies control and lowers costs compared to traditional designs. Additionally, a new phase-modular three-phase AC-DC converter is proposed, using single-stage LLC converter modules. This design offers significant improvements in efficiency and power density over the commonly used two-stage systems. The thesis also introduces an accurate design method for the three-phase AC-DC converter, using time-domain modeling to reduce energy losses and improve efficiency. A new control method is proposed for high output voltage AC-DC converters, using a microcontroller instead of the usual integrated circuits used for low output voltage conditions. Furthermore, a power balancing method with integrated power factor correction (PFC) is presented, ensuring high performance even in systems with unbalanced three-phase voltages, while minimizing the need for large output capacitors. These contributions are supported by thorough analysis, including computer simulations and experimental results, which validate the proposed designs and demonstrate their practical applications. The solutions presented improve system complexity, ease of implementation, manufacturability, cost, and performance, particularly in terms of efficiency and power density. Overall, this thesis advances the understanding of resonant converter technologies and demonstrates practical innovations that could shape future designs in power conversion.