A Modulation Method to Realize Sinusoidal Line Current for Bidirectional Isolated Three-Phase AC/DC Dual-Active-Bridge Converter Based on Matrix Converter

A high-frequency link three-phase ac/dc converter based on matrix converter is widely studied because of its small size of passive components, and some modulation methods have been proposed. However, these methods have not achieved zero-voltage-switching (ZVS) and sinusoidal line currents under bidirectional operation with PQ control. This article presents a new modulation method to realize ZVS and sinusoidal line currents under bidirectional operation by accurate control parameters (duty cycle and phase shift) for high-frequency link bidirectional three-phase ac/dc dual-active-bridge (DAB) converter. The converter can realize ZVS by phase-shift-modulation similarly to the dc/dc DAB converter. The line currents have nonlinear characteristics to phase shift and duty cycle. Therefore, the proposed method uses a nonlinear mathematical model to determine the accurate duty cycle and phase shift in order to realize sinusoidal line currents. The accurate duty cycle and phase shift are determined by real-time numerical calculation. Experimental results employing a 1-kW laboratory prototype verify the capability to control active and reactive power with sinusoidal line current. It is confirmed that the proposed method can realize the sinusoidal line current with total harmonic distortion of less than 4% under the bidirectional operating condition at the rated power.