This paper presents a new configuration for integrated on-board battery chargers of electric vehicles (EVs) incorporating symmetrical six-phase machines. The configuration proposes an exclusive utilization of a nine-switch converter (NSC) along with the machine windings during both propulsion and charging of EVs. The proposed configuration has the advantage of employing a reduced number of components in both the EV (on-board) and charging station (off-board), with the privilege of avoiding machine electromagnetic torque production during charging/vehicle-to-grid (V2G) mode of operation. During charging/V2G mode, the NSC is turned into a conventional three-phase pulse width modulation rectifier and is directly connected to the three-phase mains through the machine windings. Conventional three-phase transformers can be employed for galvanic isolation. Switching between propulsion and charging modes is carried out using a simple hardware reconfiguration. Control schemes for both propulsion and charging/V2G modes are elaborated, along with the principles of operation of the NSC. Experimental results are provided to validate the theoretical deductions for the different operating modes.

The emergence of fast-switching wide-bandgap (GaN, SiC) power electronics devices has enabled motor drive systems to achieve high efficiency, power density, control bandwidth and high-level of integration. However, the fast-switching speed and high switching frequency result in an increased level of motor overvoltage at both motor terminals and stator neutral. This overvoltage increases the stress across the motor winding insulation and bearings. This paper investigates three types of motor overvoltages, i.e., differential mode (DM) (phase-to-phase) motor terminal overvoltage, common mode (CM) (phase-to-ground) motor terminal overvoltage and CM stator neutral overvoltage (motor neutral to ground). Both the high switching speed (high dv/dt) effect and the high switching frequency effect on the motor overvoltage are investigated in this paper, where the high switching frequency effect has not been fully addressed in existing literature. Significant overvoltage is observed when the switching frequency or its multiples coincide with the cable or motor anti-resonant frequency. The anti-resonant behavior in the cable and motor impedance has been used to identify the overvoltage oscillation frequency and to explain the overvoltage observations for the three types of motor overvoltages. The analysis has been tested using a 7.5kW motor setup with and without a four-core cable, driven by a SiC or a GaN three-phase inverter with a switching frequency up to 250kHz and switching speed up to 40kV/μ s. In addition, the motor bearing current, which is a main cause of bearing degradation, has also been tested and the increase of bearing current is observed due to the high frequency effect.

This paper presents a dual Modular Multilevel Converter (MMC) topology that utilizes energy exchange between adjacent arm Sub-Modules (SM), operating with out-of-phase modulation. The proposed configuration is applicable to medium-voltage, high-power variable-speed drives incorporating open-end stator winding machines. A novel concept of power redistribution between adjacent SMs in the dual MMC topology is realized through high-frequency transformer-based dc-dc converter modules. This concept offers a significant reduction in the sizing requirement of the SM capacitance and the stored energy in the MMC system, while avoiding the problem of wide voltage fluctuations of SM capacitors, especially at low operating frequencies. The proposed configuration can produce dc voltage, therefore, a machine speed-range from zero speed to the rated speed is possible under the rated torque operating condition. The operating principles of the proposed dual MMC configuration are elaborated and necessary mathematical analysis is derived. Simulation and experimental results verify the concept of the proposed drive configuration.

In silicon carbide (SiC) device based motor drives, the high-voltage slew-rate ( dv / dt ) associated with the fast-switching transitions results in excessive motor overvoltage, due to the reflected wave phenomenon, which increases the motor winding insulation stress and causes premature failure while raising electromagnetic interference (EMI) problems. This article proposes a soft-switching voltage slew-rate profiling approach to mitigate the motor overvoltage in SiC-based cable-fed drives. The proposed approach optimizes the rise/fall time of the output voltage according to the cable length, without altering the switching speed of the SiC devices. Since increasing the switching rise/fall time using conventional approaches, such as increasing the gate resistance, results in an increased switching power loss, the proposed profiling approach is implemented using a soft-switching inverter. The optimum rise/fall time that can significantly mitigate the overvoltage is derived using frequency- and time-domain analysis. The auxiliary resonant commutated pole inverter (ARCPI) is adopted as an example of the soft-switching inverter to experimentally verify the proposed slew-rate profiling approach for the overvoltage mitigation. The analysis and experimental results show that the motor overvoltage is fully mitigated when the output voltage rise/fall time is set as the cable antiresonance period, i.e., four times of the wave transmission time along the cable. Furthermore, the slew-rate profiling approach along with the ARCPI reduces the switching loss and improves the EMI performance at the high-frequency region, compared with the conventional hard-switching converter. Specifically, the maximum efficiency of the ARCPI is about 99%.

This paper presents a drive system based on a modular multilevel converter (MMC) with high-frequency magnetic channels between adjacent-arm submodules (SMs), suitable for medium-voltage, high-power three-phase variable-speed machines. The configuration employs chains of dual half-bridge (DHB) modules linking adjacent SMs of three-phase symmetrical arms. The DHB modules are operating as power channels enabling energy exchange to restore the power imbalance among the SM capacitors. This allows arms' ripple-powers to be entirely decoupled through bidirectional power transfer between adjacent-arm SMs, resulting in a near ripple-free SM capacitor voltage profile. Therefore, the MMC common problem of wide voltage fluctuation across SM capacitors is comprehensively solved, independent of the operating frequency. Additionally, a significant reduction in the sizing requirement of SM capacitance is achieved. The configuration is able to drive multi-megawatt machines from standstill to the rated speed at the rated torque operating condition. The operating principle of the proposed MMC configuration is explained and necessary mathematical analysis is derived. Features and viability of the proposed drive system are verified through simulation and experimentation.

The four-switch three-phase (FSTP) inverter has been proposed as an innovative inverter design to reduce the cost, complexity, size, and switching losses of the dc-ac conversion system. Traditional FSTP inverter usually operates at half the dc input voltage; hence, the output line voltage cannot exceed this value. This paper proposes a novel design for the FSTP inverter based on the topology of the single-ended primary-inductance converter (SEPIC). The proposed topology provides pure sinusoidal output voltages with no need for output filter. Compared to traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input dc supply, where the proposed topology provides higher output line voltage which can be extended up to the full value of the dc input voltage. The integral sliding-mode control is used with the proposed topology to optimize its dynamics and to ensure robustness of the system during different operating conditions. Derivation of the equations describing the parameters design, components ratings, and the operation of the proposed SEPIC inverter is presented in this paper. Simulation model and experimental setup are used to validate the proposed concept. Simulations and experimental results show the effectiveness of the proposed inverter.