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

• Published in: PloS one 2024-06, Vol.19 (6), p.e0304464-e0304464
• Main Authors: Al-Barashi, Maged, Wang, Yongjun, Bhutta, Muhammad Shoaib
• Format: Article
• Language: English
• Subjects: Alternative energy sources; Analysis; Capacitors; Coils (windings); Computer and Information Sciences; Electric power; Electric Power Supplies; Electric power systems; Engineering and Technology; Equipment Design; Hardware-in-the-loop simulation; Harmonic distortion; High speed rail; High speed trains; Inductance; Inductors; Magnetic cores; Magnetics; Nyquist frequencies; Physical Sciences; Pulse duration modulation; Railroads; Renewable energy; Research and Analysis Methods; Switching; Systems stability; Traction; Transportation systems
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0304464

The traction converter modulation generates switching-frequencies current harmonics. The trapped filters can eliminate these switching harmonics, reducing total inductance and filter size. Nonetheless, in comparison with the typical inductor-capacitor-inductor (LCL) filter, the trap inductor needs a larger magnetic core. Moreover, the trapped filter has not been analyzed in the traction systems. This paper proposes a magnetic integrated inductor-trap-inductor (LLCL) filter to decrease the filter's size and investigate its application in traction converters. In fact, the application range of this filter is quite broad, and it can be used in various electrical power systems, including industrial power systems, renewable energy systems, transportation systems, and building power systems. The LC-trap may be formed by connecting the equivalent trap inductor, introduced through the magnetic coupling between inverter-side and grid-side inductors, in series with the filter capacitor. Furthermore, for H-bridge unipolar pulse width modulation (PWM) traction converters, the prominent switching harmonics are concentrated at the double switching frequencies. Therefore, the stability zone is expanded by moving the resonance above the Nyquist frequency. The presented filter's features and design are thoroughly analyzed. The proposed method is finally validated by the MATLAB/Simulink simulation and hardware-in-the-loop (HIL) experimental results. Compared to the discrete windings, the integrated ones can save two magnetic cores. Furthermore, the proposed filter can meet IEEE criteria with 0.3% for all the harmonics and total harmonic distortion (THD) of 2.15% of the grid-side current.