Applied Power Conversion [ECL4015]

A public project archive for coursework on resonant power conversion, soft-switching design, and simulation-based converter verification.

This page summarizes the core engineering work carried out for the LLC resonant DC-DC converter design project and the accompanying seminar work.

Overview

• Course: Applied Power Conversion [ECL4015]
• Focus: LLC resonant DC-DC converters, zero-voltage and zero-current soft switching, resonant-network and magnetics design, frequency-domain gain analysis, semiconductor loss and efficiency estimation
• Main tools: PSIM (switching-level simulation and verification), MATLAB (analytical parameter exploration), datasheet-based component selection

Project — LLC Resonant DC-DC Converter for an EV On-Board Charger

Designed and verified an LLC resonant DC-DC converter for an electric-vehicle on-board charger (OBC) application, covering the full path from resonant-network design to switching-level simulation verification. The project ran for approximately four months as a four-person team research module.

Design targets

• Input: 800 Vdc / Output: 300, 400, 500 V / Load conditions: 25, 50, 75, 100 %
• Zero-voltage switching maintained across the specified input and output voltage range
• Maximized weighted efficiency at the nominal operating condition

Key work

• Established the resonant-network design values and derived the corresponding estimated voltage-gain curves.
• Estimated MOSFET and diode losses for each load condition and predicted converter efficiency analytically, then verified the predictions against switching-level simulation results and analyzed the sources of deviation.
• Built the PSIM simulation model and carried out the full verification set: key waveforms over four switching periods (Vab, iLr and iLm, VCr, io, and Vo including output ripple), ZVS waveforms, load-dependent efficiency curves, and weighted-efficiency verification.
• Compared a MATLAB-based analytical parameter sweep against PSIM switching-level results, identified the harmonic content neglected by the analytical approximation as the cause of the discrepancy, and fixed the final parameter set from waveform-based simulation instead.
• Adjusted the resonant frequency so that the switching frequency stays away from the upper range near 150 kHz at the low output-voltage condition.
• Designed and verified the dead-time interval, including the simulation settings required to resolve it in the waveforms (print step in addition to the solver time step), and confirmed its effect on ZVS.