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ISOLATED SEMI-INTEGRATED ON-BOARD BATTERY CHARGER FOR EVs

BatteriesElectric vehiclesElectrical tractionGalvanic isolationIntegrated battery charger

Introduction

The patent proposes a semi-integrated on-board battery charger for electric vehicles equipped with a six-phase electric motor drive fed by two three-phase inverters. The charger ezploits the traction motor and the two inverter units at charging stage, guaranteeing galvanic isolation and sinusoidal grid current at unitary power factor. The integration permits cost, volume and weight reduction.

Technical features

The ISI-OBC is a concept of battery charger integrated with the traction drive of an electric vehicle. The invention is suited for vehicles equipped with six-phase electric drives, composed of two three-phase sets electrically isolated, independently from the type of adopted motor. At charging stage, the drive is properly reconfigured. One of the two inverters is connected to the grid (single or three-phase) while the correspondent motor winding set is connected to a diode bridge. The second three-phase inverter, the motor and the diode bridge act as an isolated DC/DC converter, where the two three-phase sets of the motor are the primary and secondary side of the equivalent high frequency transformer. The induced voltage on the secondary side, rectified by the diode bridge, charges the vehicle battery. Custom strategies were developed for maximizing the charger efficiency avoiding torque production during charging.

Possible Applications

  • Electric and plug-in hybrid cars;
  • Heavy duty electric vehicles;
  • Light electric traction.

Advantages

  • Reduction of number of components on-board of the vehicle;
  • Reduction of volume and weight;
  • High reliability;
  • Compatibility with single and three-phase main inlet;
  • Galvanic isolation of the battery, eliminating common mode currents;
  • Optimal control of the grid current waveform.