Switching Losses

Voltage source converter based high-voltage direct current systems (VSC-HVDCs) are often used in transmission and distribution regions and accomplish good operating results. They are popular due to the recent innovation of controllable semiconductor devices and bulk power transmission for long distances of about 500 km and above. However, the loss contributions of VSC-HVDC systems are relatively high compared to the traditional LCC-based HVDCs, which tends to be the main hurdle to the application of VSC-HVDC to high power transmission. Thus, the loss characteristics of VSC warrants further investigation. In this paper, the loss calculations of two level and three level VSC-based HVDC technologies are studied and corresponding loss reducing measures are obtained from the results. An essential step in the thermal management design of the power electronic devices, in this case, an insulated-gate bipolar transistor (IGBT) and diode, is required for accurate calculation of both conduction and switching losses of these devices. In order to achieve optimized designs, tools are needed for accurate prediction of device junction temperature and power dissipation. Therefore, according to IEC 61803 (Determination of power losses in HVDC converter stations), the loss calculation models of converter station equipment under operation and standby mode are established in detail alongside the datasheet parameters of the devices.

DC-DC converters are devices which convert direct current (DC) from one voltage level to another by changing the duty cycle of the main switches in the circuits. These converters are widely used in switched mode power supplies and it is important to supply a constant output voltage, regardless of disturbances on the input voltage. In this work, the performance of three different converters such as Single-Ended Primary-Inductance Converter (SEPIC), Luo converter and ZETA converter have been analyzed. Further, the parameters values such as ripple voltage, switching losses and efficiency of the proposed three different converters were compared with each other. Also, the simulation work has been carried out using MATLAB/SIMULINK software. From the comparison of obtained results, it is observed that the ZETA converter has high significance than the SEPIC and Luo converter.

This paper presents an analytical comparison between two-level inverter and three-level neutral point diode clamped inverters for electric vehicle traction purposes. The main objective of the research is to declare the main differences in the performance of the two inverter schemes in terms of the switching and conduction losses over an entire domain of the modulation index and the phase angle distribution, steady-state operation, transient operation at a wide range of speed variation, and the total harmonic distortion THD% of the line voltage output waveform. It also declares the analysis of the three-level neutral point diode clamped inverter (NPCI) obstacle and the unbalance of the DC-link capacitor voltages. The introduced scheme presents an Induction Motor (IM) drive for electric vehicle (EV) applications. Considering the dynamic operation of the EV, the speed of the three-phase induction motor is controlled using a scalar V/Hz control for the full range of the IM power factor (PF). A comprehensive MATLAB/Simulink model for the proposed scheme is established.

In the production of high quality materials by a heat treatment, it is indispensable to accurately predict the temperature inside the furnaces being employed. Mathematical modelling allows one to optimize the operating conditions of currently existing installations and the design of new ones. In this work we develop a turbulent combustion model for the heat being released by gas burners inside a shaft kiln. Various industries use such kilns to harden clay into objects such as pottery and brick stones. Turbulent combustion is the strongly coupled phenomena of the chemically reacting fuel and oxygen in a turbulent flow. In COMSOL Multiphysics® we model the turbulent flow by a Reynold-Averaged coupled with a k-epsilon turbulence model. The concentration of the chemical species such as methane, oxygen and water are tracked by mass transport equations. The corresponding source terms are represented by the eddy-breakup model. We developed a model for both the empty kiln and the kiln filled with clay-like material being processed. In the latter the material is represented as a porous medium. Numerical results for the empty kiln show a strong temperature gradient near the walls close to the inlet of the kiln. This temperature profile is shown in Figure . The presence of the material tends to smooth the temperature gradients as shown in Figure . Further work is required to refine the model representing the material inside the oven and its absorption of heat.