A Novel Control Strategy Integrating PWM and Δ-Σ PDM of Matrix Converters for Wireless Power Transfer Systems

This paper presents a novel control strategy for matrix converters in wireless power transfer (WPT) systems. Matrix converters can generate high-frequency AC from commercial AC in a single stage and are suitable for the primary power converter in WPT systems. The matrix converter-based WPT circuit topology offers a compact size and long lifetime, generally based on a pulse width modulation (PWM) strategy. The PWM strategy achieves power transmission by adjusting the pulse width of high-frequency voltage; it is easy to implement and enables high-quality grid currents. In this paper, a control strategy that integrates PWM and pulse density modulation (PDM) is proposed for more efficient power transmission. The proposed strategy, which achieves power transmission by adjusting the pulse width and pulse density, is expected to suppress switching losses by reducing the switching frequency. The pulse pattern is determined based on Δ-Σ modulation, which enables continuous power control and suppression of power fluctuations. This strategy can achieve high system efficiency and high-quality grid currents. Experiments conducted using a 2.5 kW prototype system demonstrated the effectiveness of the proposed strategy.