Power Quality Enhancement in Grid-Connected EV Charging Stations Using SRF-Based Shunt Active Power Filter

Abstract

Contemporary electric vehicle (EV) charging infrastructure heavily relies on nonlinear power electronic converters that inject harmonic currents into the distribution network, significantly deteriorating power quality. This paper addresses the harmonic mitigation challenge in a three-unit EV charging station through the deployment of a Shunt Active Power Filter (SAPF) governed by the Synchronous Reference Frame (SRF) algorithm. The proposed topology employs a two-level IGBT-based Voltage Source Inverter (VSI) coupled to the AC bus through a filter inductance, with the DC link pre-charged to 750 V via a capacitor bank. The load configuration incorporates three EV stations: EV Station 1 and EV Station 3 operate continuously from t = 0 s (each targeting approximately 500 V battery terminal voltage), while EV Station 2 connects at t = 0.1 s and disconnects at t = 0.65 s to emulate real-world intermittent charging dynamics. The SRF controller transforms load currents to a rotating d-q frame, isolates harmonic components via low-pass filtering, and derives reference compensating currents through inverse transformation. Extensive MATLAB/Simulink simulations demonstrate that source current THD is reduced from 29.53% (uncompensated) to 5.57% (with SAPF), representing an 81.1% reduction. Power factor concurrently improves from 0.9926 to 0.9971. EV battery terminal voltages stabilize near the target 500 V. The simulation results validate the effectiveness of the proposed SAPF configuration for practical EV charging environments. The proposed system demonstrates stable harmonic compensation under dynamic EV load conditions.

Introduction

This paper presents a power quality solution for electric vehicle (EV) charging stations using a Shunt Active Power Filter (SAPF) controlled by a Synchronous Reference Frame (SRF) method.

The motivation is that large-scale EV charging introduces significant harmonic distortion into the electrical grid due to diode-bridge rectifiers used in chargers. While individual chargers may meet standards like IEEE 519-2014 (THD < 5%), multiple chargers operating together can collectively exceed acceptable harmonic limits, leading to issues such as poor power factor, transformer heating, and grid instability.

To address this, the study designs and simulates an SRF-based SAPF in MATLAB/Simulink for a multi-charger EV station. The system includes three EV charging units, with one dynamically switching on and off to simulate real-world fluctuating load conditions. The SAPF uses a voltage source inverter (VSI), DC-link capacitor, and filter inductors to inject compensating currents at the point of common coupling (PCC).

The control strategy is based on the SRF method, where load currents are transformed into a rotating d–q reference frame using Park’s transformation. In this frame, the fundamental component becomes a steady DC value, allowing harmonic components to be isolated using low-pass filtering. These harmonics are then converted back into three-phase compensating currents, which the SAPF injects to cancel distortion in real time.

The literature review shows that while active power filters and SRF control are well established, there is limited work specifically addressing multi-unit EV charging stations with dynamic load variation, which this study targets.

Conclusion

This paper has presented the design and simulation of a Synchronous Reference Frame-based Shunt Active Power Filter for harmonic mitigation in a multi-unit EV charging station with dynamic load variation. The proposed SAPF architecture employs a two-level IGBT VSI with a pre-charged 750 V DC capacitor, governed by an SRF harmonic extraction algorithm and PI DC bus regulator. Simulation results in MATLAB/Simulink substantiate that source current THD is reduced from 29.53% to 5.57%—an 81.1% improvement—while power factor improves from 0.9926 to 0.9971. Both EV battery terminal voltages stabilize near the 500 V target at 528.1 V, confirming improved power delivery quality. The SRF controller demonstrates stable harmonic compensation throughout the dynamic load variation introduced by EV Station 2 (connect at t = 0.1 s, disconnect at t = 0.65 s). The marginal deviation of 5.57% from the IEEE 519-2014 limit of 5% is attributable to transient dynamics and can be addressed through controller parameter optimization. Future work will target: (i) hardware implementation on a DSP-controlled prototype, (ii) adaptive PI tuning for improved transient THD performance, (iii) extension to unbalanced and weak grid conditions, and (iv) integration of energy storage or renewable sources at the DC link for enhanced grid support capability. The proposed SAPF system demonstrates robustness and effectiveness under realistic EV charging scenarios involving dynamic load variations.

References

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Copyright

Copyright © 2026 Pratik Potdukhe, Prof. Praful Tadse. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.