Simulation and realization of LLC charger with planar transformer in aviation applications

This thesis presents the end-to-end design, digital control, simulation, and experimental validation of a high-efficiency LLC resonant charger with a wide regulation range for aircraft batteries interfaced to a 270 VDC bus. Driven by stringent mass/volume constraints and reliability targets in aviation, soft-switching and step-up capability are required; the LLC topology is therefore adopted as it natively supports CC/CV (Constant Voltage/ Constant Current) charging. The design proceeds from battery-imposed requirements and the 270 VDC input interface. The resonant tank is dimensioned by extracting m (Inductance ratio), Q (Quality factor), and R_ac (Equivalent AC resistance) from voltage-gain curves. After selecting fr (Resonant frequency), Lr (Resonant inductance), Cr (Resonant capacitance), and Lm (Magnetizing inductance) are computed and then refined with practical component choices. Selection criteria for a high-frequency planar transformer are defined, suitable Si/SiC switching devices are assessed, and the output rectification architecture is chosen to maximize efficiency and to interface cleanly with digital control. Control uses frequency modulation with a PI regulator to realize closed-loop current and voltage regulation via a pulse-frequency modulator. Operation at, above, and below resontracksis analyzed in simulation; the results show that the topology and the implemented digital closed loop track the CC/CV profile appropriately for battery charging. Experimental work on a laboratory prototype confirms soft-switching conditions, the gain–frequency behavior, and CC/CV regulation. The measurements meet the targeted efficiency and operating range, and they align with the simulated trends. Chapter 1 explains the project aim and literature survey, Chapter 2 motivation for aviation electrification, battery history, the role of charging systems, and the rationale for resonant conversion. Chapter 3 states, the 270 VDC and battery-driven requirements, and the basis for topology selection. Chapter 4 presents the high-level architecture and block diagrams for power and control/data flow. Chapter 5 details the LLC structure, resonant-tank equations and workflow, computation of Lr, Cr, Lm, and the transformer, semiconductor, and rectification choices. Chapter 6 describes the digital controller platform, frequency-modulation strategy, and PI-based closed-loop design. Chapter 7 reports the simulation setup, gain-curve extraction, and CC/CV performance analyses. Chapter 8 provides prototype test results.