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As the switching frequency of power semiconductor devices increases, it is necessary to suppress the common-mode voltage (CMV) generated by the pulsewidth modulation action of the voltage-source inverters, which can produce serious electromagnetic interference (EMI) and hazards, such as motor axial current. This article proposes a modified modulation technique based on the single-edge carrier form to decrease the amplitude and frequency of CMV by selecting different combinations of active voltage vectors in different voltage vector sectors. On this basis, the method of optimizing the sequence of voltage vector action is adopted to reduce the switching losses of the inverter and designing a reasonable carrier frequency variation function based on the mathematical derivation, considering the phase angle of output current and distribution characteristics in the time domain of switching frequency, which is combined with the above-modified modulation strategy to further restrain the switching losses and differential-mode conducted EMI. Moreover, a deadtime effect correction methodology for estimating the phase current at the moment of switching action is introduced to eliminate the CMV spikes during the deadtime interval. Finally, the experimental platform is built to validate the effectiveness and practicality of the modified single-edge modulation technique.

This paper presented an improved switching transient model of silicon carbide (SiC)-based asymmetric H-bridge (AHB) power converter for a switched reluctance generator (SRG), which takes the nonlinear phase inductance of the SRG into consideration. First, a systematic mathematic derivation is carried out and the switching transient model is established. Second, the impact of the nonlinear phase inductance of the SRG on switching transients is verified by PSpice & Simulink co-simulations. Third, a power loss model is established by the transient model through PSpice & Simulink co-simulations. The model is conducted to indicate the power loss characteristics of the SiC-based AHB power converter. Simulation results indicate that the nonlinear phase inductance of the SRG is able to accelerate the switching speed of SiC-MOSFETs, and that the SiC converter is advantageous in terms of power loss. Experimental results illustrate that the established power loss model experiences high accuracy. In addition, SiC devices are able to strengthen the power density and efficiency of a converter while reducing its heat dissipation requirements.

Purpose: This paper aims to present a novel position sensorless control scheme with fault-tolerance ability for switched reluctance motor at low speed. Design/methodology/approach: First, the detection pulses are injected in the freewheeling and idle intervals of each phase. Second, the aligned position of each phase can be detected by comparing the consecutive rise time of detection current. Third, the whole-region rotor position and real-time rotational speed can be updated four times for the improvement of detection accuracy. Finally, the fault-tolerant control strategy is performed to enhance the robustness and reliability of proposed sensorless scheme under faulty conditions. Findings: Based on proposed sensorless control strategy, the estimated rotor position is in good agreement with the actual rotor position and the maximum rotor position error is 1.5°. Meanwhile, the proposed sensorless scheme is still effective when the motor with multiphase loss and the maximum rotor position error is 1.9°. Moreover, the accuracy of the rotor position estimation can be ensured even if the motor is in an accelerated state or decelerated state. Originality/value: The proposed sensorless method does not require extensive memory, complicated computation and prior knowledge of the electromagnetic properties of the motor, which is easy to implement. Furthermore, it is suitable for different control strategies at low speed without negative torque generation. [ABSTRACT FROM AUTHOR]