High-frequency harmonics suppression in high-speed railway through magnetic integrated LLCL filter

Area of Science:

• Electrical Engineering
• Power Electronics
• Electromagnetic Compatibility

Background:

• Traction converter modulation generates current harmonics, necessitating effective filtering solutions.
• Existing inductor-capacitor-inductor (LCL) filters face challenges with filter size and magnetic core requirements.
• Trapped filters offer harmonic elimination but lack analysis in traction systems.

Purpose of the Study:

• To propose and analyze a magnetic integrated inductor-trap-inductor (LLCL) filter for traction converters.
• To reduce filter size and investigate its application in electrical power systems.
• To address the limitations of traditional filters in harmonic suppression.

Main Methods:

• Development of a magnetic integrated LLCL filter utilizing magnetic coupling.
• Analysis of filter design and features for H-bridge unipolar pulse width modulation (PWM) traction converters.
• Validation through MATLAB/Simulink simulations and hardware-in-the-loop (HIL) experiments.

Main Results:

• The LLCL filter effectively suppresses switching frequency current harmonics.
• The integrated design saves two magnetic cores compared to discrete windings.
• Achieved IEEE criteria compliance with 0.3% for individual harmonics and 2.15% total harmonic distortion (THD).

Conclusions:

• The proposed LLCL filter is a viable and efficient solution for harmonic mitigation in traction converters.
• The magnetic integration offers significant size and core reduction benefits.
• The filter demonstrates broad applicability across various electrical power systems.