Advanced Step Density Modulation Technique to Reduce Current Ripples in High-Frequency Inverter for WPT EV Charging Systems

Abstract

This paper analyzes Step Density Modulation (SDM) technique for high-frequency inverters in Wireless Power Transfer (WPT) systems for Electric Vehicle (EV) charging. While Pulse Density Modulation (PDM) is commonly used to control high-frequency inverters, it faces limitations in managing current ripple, leading to electromagnetic interference (EMI), reduced power transfer efficiency, and system performance degradation. Step Density Modulation is proposed as an advanced alternative to PDM, offering dynamic pulse density adjustments in discrete stages to align with inverter switching characteristics. This approach minimizes the effects of dead time, significantly reducing current ripple and total harmonic distortion (THD), thereby enhancing waveform quality and system efficiency. A comprehensive mathematical model compares current ripple magnitude, harmonic spectrum, and inverter delay time for both modulation techniques. MATLAB simulations, validated through hardware prototype implementation on a 5 kW WPT EV charger, demonstrate that SDM reduces current ripple by up to 30% and THD of 20% compared to PDM. The hardware prototype confirms smoother inverter output, improved power stability, and increased efficiency, establishing SDM as a reliable and practical solution for enhancing WPT systems in EV charging applications.