Electric vehicle (EV) is a promising solution to alleviate energy crisis and environmental pressure, as well as energy efficiency. The battery pack is a key unit in EVs, which can be charged by different chargers, such as integrated on-board charger and wireless charger. Actually, the integrated on-board charger becomes more and more attractive in recent years, because the propulsive system is engaged in the charging system to reduce the cost and volume. Also, the wireless EV charger is convenient and safe because of no physical contact. In this thesis, the advanced charging technologies, including integrated on-board EV chargers and wireless EV chargers are both in-depth investigated and studied.

Firstly, two kinds of three-phase integrated on-board EV charging systems are explored, where the motor windings are reutilized as the chopper inductors. Since the direct current (DC) flows through the three-phase permanent magnet synchronous machine (PMSM), the rotational movement, extra noise and motor wear are generated due to the charging torque. In order to keep the vehicle safe, the universal expression of charging torque is derived and analyzed. The safe charging operation is investigated, which provides an effective solution to significantly minimize the charging torque.

Secondly, an effective charging-torque elimination method is proposed for six-phase integrated on-board EV chargers, where the propulsive inverter and six-phase motor windings are reutilized as a six-phase rectifier and filtering inductors. The charging torque is inevitable to produce as the alternating currents (AC) pass via the motor windings. A numerical method is adopted to discover all possible charging torque elimination positions. Grid requirements are met based on the unity power factor correction and zero-sequence current control.

Thirdly, an electrolytic capacitor-less wireless power transfer (WPT) charging system is proposed to remove the short-lifetime capacitor and improve the power density. The high-frequency voltage is transferred from 50Hz grid voltage with a matrix converter. The space vector modulation is developed to modulate the load voltage while maintaining the grid side performance.

Fourthly, a multi-frequency WPT system is presented for future application, which can deliver power to multiple receivers simultaneously by employing three-phase high-frequency inverter with delta type transmitting tanks. In addition, three additional resonant frequencies are obtained by rebuilding equivalent resonant tanks. Six independent frequencies transmission, six kinds of concurrent double frequencies transmission, and one concurrent ternary frequency transmission are performed and analyzed.