The study of five-level inverters with the various PWM
The energy indicators of multilevel voltage converters are analyzed. The relevance of the research is indicated by the increasing demands of technological processes for the economic use of electric energy, the reduction in power consumed by semiconductor converters, and also to the level of regulated reactive power. The converter considered is a five-level voltage inverter. As the topology of the converter, the structure of the inverter on H-bridges is considered. The article presents two-stage three-phase circuits with the connection of inverter cells to wye. Possible states of electronic keys and their corresponding operating modes are described. The voltage of constant voltage sources is 535 V. In the article algorithms for the formation of pulse-width modulation (PWM) are considered: Phase Opposition Disposition, Alternative Phase Opposition Disposition and Hybrid methods with zero sequence sinusoidal shape of the modulate voltage or with triangular shape of the modulate voltage. As a criterion for evaluating the quality of the inverter's output voltage, total harmonic distortion and line-to-line voltage were adopted. A harmonic voltage spectrum is developed for various control methods of the converter. Possible ways of reducing the harmonic coefficient, as well as increasing the amplitude modulation factor, are shown, by using various methods of forming the pulse-width modulation.
Comparative analysis of modified multilevel DC link inverter with conventional cascaded multilevel inverter fed induction motor drive
Abstract This paper focuses a new modified multi-level DC link inverter with reduced switches. It presents a comparative analysis of the modified inverter with the existing cascaded H-bridge multilevel inverter (CHBMLI) fed with induction motor drive. The modified multilevel dc link inverter (MLDCL) which is proposed greatly minimizes the switch count as well as the number of gate drivers compare to other family of multilevel inverters. PWM technique which has been applied for proposed inverter and CHBMLI is level shifted multi carrier PWM. An exhaustive survey has taken to investigate the performance characteristics such as total harmonic distortion (THD) and efficiency of various levels of inverter. For the meticulous analysis eleven-level DC link inverter and the existing eleven-level CHBMLI are built using MATLAB/SIMULINK platform. The proposed inverter is observed to have a better performance and relatively less cost compared with the conventional scheme.
Frequency selective surface design for blinds applications
In this paper, the reconfigurable blind structure with frequency selective surfaces(FSS) for the building applications are presented. Frequency transmission characteristics for different angles of the proposed blind-FSSs are investigated and verified through simulation and measurement. The simulation results show that we can implement the reconfigurable blind-FSS for multiband wireless applications. To verify the proposed paper, two kinds of blind-FSSs, crossed dipole FSS and circular ring FSS are fabricated and measurements are performed for different angles. The proposed structure in this paper which is very simple, can be easily applied to any planar surface for wireless security applications at low cost.