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This paper proposes a novel three-phase voltage source inverter dead-time compensation strategy for accurate compensation in wide current regions of the inverter. In particular, an analysis of the output voltage distortion of the inverter, which appears as parasitic components of the switches, was conducted for proper voltage compensation in the low current region, and an on-line compensation voltage controller was proposed. Additionally, a new trapezoidal compensation voltage implementation method using the current phase was proposed to simplify realizing the trapezoidal shape of the three-phase compensation voltages. Finally, when the proposed dead-time compensation strategy was applied, the maximum phase voltage magnitude in the linear modulation voltage regions was defined to achieve smooth operation even at high modulation index. Simulations and experiments were conducted to verify the performance of the proposed dead-time compensation scheme.

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Gallium nitride (GaN) devices have been widely adopted to achieve high efficiency and high power density as alternative solutions to silicon devices. When the GaN power devices are used for variable frequency drive (VFD) systems, the high dv/dt pulses at the motor terminal, which induce shaft voltage and common mode current, should be carefully considered to ensure system reliability. Although the high dv/dt issues can be mitigated with a dv/dt filter method, it leads to performance degradation depending on cable length. Meanwhile, a matrix converter also becomes a next-generation power converter for the VFDs which has a regeneration capability and unity power factor. Thus, this paper discusses the GaN-based matrix converter for the VFD as a study case considering the motor terminal voltage quality and the common mode current. Also, a sine wave filter is adopted to cope with the terminal voltage quality irrespective of cable length. The optimized design procedure of the sine filter considers practical issues. Experimental results are presented to suggest a suitable solution for the GaN-based VFDs in accordance with the cable length.

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This paper proposes a pulse width modulation (PWM) strategy for improving the efficiency of a 5-level H-bridge T-type neutral point clamped (TNPC) inverter. In the case of the proposed PWM strategy, unlike the conventional PWM strategy in which both of the switching legs of the H-bridge inverter operate at a high frequency, one switching leg of the inverter operates at a low frequency. As the switching frequency is lowered, the switching loss is reduced, this improving the efficiency of the system. The duty references for the switching legs and the operating principle of the inverter are described in detail. The proposed PWM strategy, however, causes distortion of the output filter inductor current. The cause of the distortion has been analyzed and a compensation method is proposed to mitigate the distortion of the current. The effect of the proposed PWM strategy can be predicted through the loss calculation of the inverter for each modulation strategy. Furthermore, current distortion mitigation obtained by compensation method is confirmed through the simulation. In order to verify the effectiveness of the proposed strategy, a 2 kW H-bridge TNPC inverter prototype is implemented and tested. The simulation and experimental results show that the efficiency of the inverter is improved when the proposed PWM strategy is applied.

This paper introduces a gallium nitride (GaN) high electron mobility transistor (HEMT)-based matrix converter for motor friendly drive systems. A fast switching characteristic of the GaN devices causes high dv/dt. This increases the importance of noise immunity and the reduction of parasitic components in system design. In addition, the high dv/dt in motor drive systems leads to voltage spike at a motor input terminal and leakage current through a motor chassis. Accordingly, a gate drive circuit consists of devices with a high common mode transient immunity. A printed circuit board was designed to minimize parasitic inductance, which was analyzed by performing simulations. To mitigate the dv/dt of the voltage applied to the motor and the leakage current, a dv/dt filter and a sine-wave filter were utilized as an output filter of the matrix converter. The effectiveness of each filter was verified by driving an induction motor.