Abstract: High-power DC fast charging (22–350 kW) requires grid-connected power converters capable of delivering bidirectional power flow, low harmonic distortion, and unity power factor operation. Two-level Active Front-End (AFE) converters are widely adopted in such systems due to their simplicity and cost advantages. However, their performance is strongly dependent on the design of the grid-interface LCL filter. Although LCL filters provide excellent attenuation of switching harmonics, they introduce resonance that must be mitigated through appropriate damping.

In this work, a bidirectional AFE converter with an RC-damped LCL filter is designed and implemented. While the RC damping approach ensures effective resonance suppression and low harmonic distortion, it is observed that at high power levels, the damping resistor dissipates significant power. This leads to increased thermal stress and requires a bulky resistor and heat-sink design.

This practical limitation motivates a detailed comparative investigation of different damping strategies suitable for high-power applications. To address this, a unified analysis of four damping methods R, RC, RLC, and capacitor current feedback (CCF) based on active damping is carried out under identical LCL filter parameters.

The system is modelled and controlled using a 𝑑𝑞-axis current control scheme with PLL-based synchronization. The performance of each damping method is evaluated in terms of resonance suppression, total harmonic distortion (THD), damping losses, and dynamic stability using Typhoon HIL real-time validation. This work provides design-oriented insights and practical guidelines for selecting appropriate damping strategies in high-power grid-connected converters, emphasizing the trade-off between efficiency, complexity, and stability.

Keywords: Bidirectional Active Front-End (AFE) converter, LCL filter, resonance damping, capacitor current feedback (CCF), harmonic distortion, dq-axis current control, Typhoon HIL, high-power EV charging.

All are cordially invited.

Event Details
Title: Design and Comparative Analysis of Damped LCL Filters for High-Power Bidirectional Active Front End Converters
Date: May 25, 2026 at 09:30 AM
Venue: Google Meet (http://meet.google.com/ewn-uyso-yyv)
Speaker: Mr. THANGAMUTHU N (EE22S093)
Guide: Dr. Lakshminarasamma N
Type: MS seminar

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