10kW DC-DC LLC resonant converter design for 48V DC load application

• Main Author: Pataballa Seshasai Kumar
• Other Authors: Josep Pou
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/157290
• Institution: Nanyang Technological University

Due to the global demand for, high efficiency, high power density, reduced electromagnetic interference(EMI) from a power converter, especially in the segments like electrification of aerospace, metro, domestic automobile segments, wireless-charging, LLC resonant converters have gained significant attention, research and development in the recent years. However, the design of resonant converters is still considered mystical and poorly understood, difficult to obtain an accurate model as the converter has a high degree of design-freedom, adopts the rule of thumbs, and intensive circuit analysis. Thus, the power electronics(PE) scientific community started designing using approximated models like first harmonic approximation(FHA). This model assumes that the switching frequency is equal to resonant frequency thus, the tank filters all higher-order harmonics in the excitations, and the analysis is done considering the fundamental sinusoidal components only. However, the analysis varies when the converter functions above or below the resonant frequency. Thus, it arises the necessity to estimate the deviation in analytics and design the converter optimally. After resorting to adequate bibliography, an indigenous design flow chart for the converter is proposed in this dissertation. Unlike in most designs, FHA analysis here is utilized only to estimate the device stress while the parameters of the converters are designed intuitively adhering to the proposed flow chart. Emphasis is laid on step by step understanding of the insights with sheer derived analytics, comparing every calculation and design stage through PSIM simulation. A 10kW rated converter is considered for the design. The flow goes through defining boundary conditions, analytical design, open-loop stimulation, FHA analysis, feed-forward control implementation, devices selection, thermal modelling, losses estimation, modifying the secondary bridge topology (improving the peak full load efficiency to 97.37% from 95.57%), closed-loop control implementation. With these stages, a clear analytical design insight of LLC resonant converter is demonstrated and validated using PSIM Simulation.