Analysis and Conceptualization of a Single-Phase Buck-Boost Integrated EV On-Board Charger Based on a Double Bridge Inverter Drive System

Integrated on-board chargers (iOBCs) typically exploit the traction drive system (i.e., inverter and motor) of an electric vehicle (EV) as a battery charging interface. The main goal of iOBCs is to reduce cost and footprint of the EV charging system by leveraging existing powertrain components. However, this integration comes with unique challenges (e.g., limited efficiency, possible torque production, EMI, electrical safety, etc.), which currently represent an active research topic for both industry and academia. The main shortcoming of most existing iOBC solutions is that they only provide voltage step-up (boost) or voltage step-down (buck) capability, thus requiring an additional DC/DC conversion stage to address the full battery voltage range. This paper introduces a novel single-phase iOBC topology with inherent buck-boost capability, exploiting a next-generation 400 V double bridge inverter EV drive system. This topology allows for universal mains interface charging (i.e., 230 V EU, 120 V/240 V USA, etc.) and can exploit all kinds of synchronous/asynchronous electrical machines with an open-end winding configuration. The proposed iOBC structure only requires an additional line-frequency diode bridge rated for the charging current (or an active synchronous rectifier, if bidirectional charging is desired), an input filter capacitor and two reconfiguration switches. In this paper, the operating principle of the proposed iOBC is described, the stresses on all system active and passive components are analyzed and the converter closed-loop control strategy is introduced and assessed in simulation. Furthermore, a novel control approach addressing the double-line frequency power pulsation (i.e., typical of single-phase chargers) is proposed, exploiting the magnetic energy storage capability of the electrical machine.