Enhancing High-Frequency Inverter Performance in WPT EV Charging Systems by Reducing Current Ripple Through Step Density Modulation Techniques

This paper analyses Step Density Modulation (SDM) techniques for high-frequency inverters in Wireless Power Transfer (WPT) systems for Electric Vehicle (EV) charging. Pulse Density Modulation (PDM) is widely used to control high-frequency inverters, but it struggles to manage current ripple, which can cause EMI, power transfer efficiency loss, and system degradation. In this paper, Step Density Modulation is offered as an upgrade over standard PDM to reduce effects of dead time in inverters by providing more precise pulse density and timing control. PDM modifies pulse density evenly, whereas Step Density Modulation dynamically varies pulse density in discrete stages to match the inverter's switching characteristics. Current ripple and harmonics are reduced, enhancing waveform quality and power transfer efficiency. A thorough mathematical model compares current ripple magnitude, frequency spectrum, and inverter delay time for the two modulation techniques. Detailed MATLAB models simulated on a 5 kW WPT EV charger show that Step Density Modulation outperforms PDM in reducing current ripple and improving inverter performance. Step Density Modulation reduces current ripple by 30% more than PDM, smoothing inverter output and improving system stability. This innovative modulation scheme improves WPT system efficiency and reliability for EV charging applications.