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- Soft Switching of IGBTs in Lagging Lag of ZVT Phase Shift DC/DC Converter
- Multilevel Inverters Harmonic Elimination with Non-Equal DC Voltage Sources Using Linear Fuzzy Programming
- State Observer for Grid-Voltage Sensorless Control of a Grid-Connected Converter Equipped With an LCL Filter
- Enhancement of the new HVDC auto transformer for inherent DC fault clearing capability
- Low Cost Torque Ripple Reduction in SRM Utilizing Resonance Phenomenon in Order to Optimize the Current and Torque Profile
EPE Journal Volume 25-3 - Papers
By Sandra Zeljkovic, Tomas Reiter, Dieter Gerling
The additional effort to achieve zero voltage transition (ZVT) in the lagging leg of a frequently used ZVT phase shift full bridge converter can be avoided by designing the converter with ‘high speed’ trench fieldstop IGBTs. Thanks to their reduced turn-off but at the same time low turn-on losses, the loss of ZVT in the lagging leg is not anymore critical to converter’s efficiency. Moreover, it can be beneficial due to their improved ‘switching to conduction loss’ ratio. Based on that conclusion, a simple method to maximize their efficiency by minimizing the resonant inductance is proposed.
By A. K. Al-Othman; Nabil A. Ahmed; M. E. AlSharidah
This paper presents a fast and effective optimal solution of harmonic elimination of multilevel inverters with unbalanced DC sources using fuzzy linear programming (FLP). A set of non-linear mathematical models containing a description of the general output waveform of cascaded H-bridge multilevel inverters with unbalanced DC sources, will be formulated. An objective function will be employed to obtain an optimal solution for a set of switching instances to eliminate undesired harmonics. The solution algorithm will also control the output voltage level at the desired fundamental component. FLP is used to obtain an accurate and fast solution to minimize the linearized objective function and identify the desired set of switching angles. The proposed fuzzy linear programming is tested both in simulation and experimentally, for different cases of multilevel inverters to verify the accuracy of the results.
By Jarno Kukkola; Marko Hinkkanen
This paper proposes a simple grid-voltage sensorless alternative to the conventional PLL synchronization for a grid-connected converter equipped with an LCL filter. The grid-voltage magnitude and angle are estimated based only on the converter current and DC-voltage measurements. Reduced number of sensors decreases costs and amount of sensor wiring. The analytically derived design is validated experimentally.
By André Schön; Mark-M. Bakran
The structural change in energy generation and distribution, especially with renewable power sources and their volatile and demand independent generation behavior in areas with low load or at the periphery of the AC grid brings various challenges. Amongst others the need to transport high amounts of power over long distances between generation and load centers brings an AC grid to its limits. Therefore High Voltage Direct Current (HVDC) power transmission is the preferable choice for that task, since compared to High Voltage AC transmission, there are no stability issues and the transmission losses are much lower. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, which still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses and high investment costs. With the newly presented HVDC-DC auto transformer [1–5]* it is possible to directly link two DC lines with different voltage levels. In this paper it is shown, that this topology is also able to securely prevent high DC fault currents and to isolate a faulty DC line at the interconnection point of different HVDC voltage levels. This ability and the resulting topological efforts are compared to the state of the art topology of linking two DC lines with different voltage levels via an AC connection.
By Rana Moeini; Mehran Rafiee; Ebrahim Afjei
Switched Reluctance Motor (SRM) is one of the best types of motors with a large number of merits; however, their torque profile faces with Torque Ripple (TR) especially in high speed which is known as an intrinsic drawback of these types of machines. The problem dramatically decreases the performance and popularity of SRMs. There are some strategies in order to reduce TR most of which are complex and expensive. In this paper, a novel low cost and simple method is presented in order to decrease TR. The method is based on using resonance phenomenon in the SRM conventional converter which is named asymmetric bridge converter or Two-Switch per Phase (TSP) converter. In the new Resonant Three-Switch per Phase (RTSP) converter, the energy stored in the phase winding discharges resonantly after switching off the phase which damps the phase current quickly. This dramatically reduces TR. After designing, the novel idea is simulated in MATLAB software and tested on a 6 by 4 three-phase SRM in laboratory. The SRM specifications are obtained by 3-D Finite Element Method (FEM) after simulation in MAGNET CAD software. Since then, the operational and simulation results of both TSP and RTSP converters are compared with each other. At the end of the paper, it has been shown that the RTSP converter not only significantly decreases the level of the generated TR but also improves the performance and efficiency of SRM.