Dual-Port Inverters With Internal DC–DC Conversion for Adjustable DC-Link Voltage Operation of Electric Vehicles

Adjustable dc-link voltage operation is an attractive solution to improve the overall efficiency of electric vehicles (EVs). This article proposes a dual-port inverter (DPI) with an internal dc-dc conversion system for the adjustable dc-link operation of the EVs. Unlike the conventional two-stage structure, the DPI provides a power flow path from the battery to the inverter directly. Hence, the power processed by the dc-dc converter can be reduced, resulting in higher efficiency and reduced power rating of the dc-dc converter. To fully explore the potential of this inverter in both high-speed and low-speed range, two operation modes with corresponding modulation strategies are investigated. A two-stage modulation strategy is proposed to produce undistorted current even in the presence of unevenly distributed and dynamically changing space vectors in the high-speed mode. Furthermore, the power processed by the dc-dc converter is minimized with the proposed two-stage modulation strategy, and the overall efficiency of the system is further improved. Experimental results with a 1.1-kW permanent-magnet synchronous motor are presented to validate the effectiveness of the proposed method.