Constraint-Aware Optimization of LCL Filters for Grid-Connected EV Charging Systems

This paper presents a constraint-aware and systematic methodology for the design of LCL filters in grid-connected electric vehicle (EV) fast chargers. The proposed step-by-step process provides analytical sizing equations for the passive components L1, L2, and C while explicitly accounting for key design trade-offs such as voltage drop, reactive power draw, resonance frequency, and harmonic attenuation. Unlike conventional practice, which often relies on oversized inductors, the proposed approach selects inductance values near the permissible lower bound, resulting in a more compact and cost-effective filter solution. A 100 kVA bidirectional converter model was used to validate the design through time-domain simulations. Results show that the proposed filter maintains a grid current total harmonic distortion of less than 2% and limits individual high-order harmonics to below 0.3%, fully complying with IEEE Std. 519 taken as reference among other power quality standards. By selecting the minimum inductance that satisfies these limits, the required inductor mass is reduced by approximately 67% compared with a conservative design, translating into substantial savings in size and cost. The methodology is scalable to other power ratings by updating the base parameters, providing a practical design tool for EV charger manufacturers and utilities to achieve higher efficiency, lower cost, and reliable grid-code compliance.