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The electronic properties of single/bi-layer SnSe are theoretically studied using first-principles approach based on density-functional theory (DFT). The band structure and lattice parameters are researched. In order to gain more desirable electronic property, the in-plane strain and external electric field are adopted to modulate their electronic properties. The simulation results demonstrate that...
In this paper, an efficiency comparison of neutral-point-clamped (NPC) inverters and bipolar switch NPC (T-Type) inverters is studied and the result shows that the T-Type inverter is more efficient at lower switching frequencies. Nevertheless, its efficiency suffers when the switching frequency increases due to high switching loss of the equipped high voltage power switches. In order to reduce switching...
This paper proposes a novel direct torque control (DTC) scheme to reduce the torque and stator flux ripples for permanent-magnet synchronous motor (PMSM) drives using a relatively low sampling frequency. Unlike the conventional DTC in which the voltage vectors are determined by hysteresis controllers, the proposed DTC uses nonlinear saturation comparators and a duty ratio modulation scheme for switch...
In this paper, a circuit-level decoupling modulation strategy is proposed for the three-level (TL) neutral-point-clamped (NPC) inverters. With the proposed modulation scheme, the TL-NPC inverter can be decoupled into two three-level Buck converters in each defined operating section, which makes the controller design much simpler. The decoupling principle including the driving signal synthesis and...
The high voltage variable frequency system has complicated structure and high power density. It comprises industrial frequency AC, DC and variable frequency AC. All of these bring new challenges to the system's protection and stability control. This paper considered the protection strategy in two aspects: device-level protection and system-level protection. Through improving the circuit structure...
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