Optimization of PWM for Overmodulation Region of Two-level Inverters

Three optimized PWM techniques for the overmodulation region of two-level inverter-fed ac drives are introduced and investigated from harmonic loss minimization point of view. The optimization is elaborated for the lowest loss-factor, which is proportional to the square of rms value of current harmonics. The loss-factors are computed for different switching numbers as the function of the motor fundamental voltage. It is shown that, respect to the motor heating and torque ripples, the acceptable drive condition can be guaranteed by relatively low value of inverter switching frequency up to 96-97% of maximal possible motor voltage. Furthermore, it is shown that, the so-called Three vector methods have considerably better performance in the lower part of the overmodulation region than the so-called Two vector method for the same number of switching. The performance of the techniques is compared with other existing PWM techniques. The paper discusses the implementation details of the proposed optimal PWM techniques. The theoretical results are verified by experimental and simulation tests

Optimal PWM for Three-Level Inverter fed High Speed Drives

Thanks to new field of applications, like high speed/high-pole drives with high rated fundamental frequency or multilevel converters powering medium or high voltage drive systems, optimized PWM techniques became again a hot topic of research interest. The current paper introduces an optimized PWM technique for three-level inverter, which can be applied to supply high speed drives at low pulse ratio. The optimization is done for the lowest loss-factor, which is proportional to the square of rms value of current harmonics. The performance of the optimal PWM technique is demonstrated by simulation and experimental tests by using a NPC type inverter

Az inverteres villamos hajtások fejlődési irányai

Az inverterről táplált villamos hajtások jelentős szerepet játszanak a korszerű műszaki berendezésekben. A cikk egy rövid áttekintést ad a villamos hajtásokban alkalmazott inverter topológiákról, az inverterekben alkalmazott modulációs eljárásokról és kapcsolóelemekről. Az elmúlt évtizedekben és években ezen területeken történt fejlesztések jelentősen hozzájárultak az inverteres hajtások fejlődéséhez és széles körű elterjedéséhez

Investigation of estimator algorithms for high speed drive systems

In high speed drives both the sampling over reference frequency ratio F and the carrier over reference frequency mf is a low value. The low mf ratio results voltage and current harmonic spectra far more unfavorable than at standard ratios. The low F ratio can result uncertainty and inaccuracy in the calculation of the magnitude and angle of stator or rotor flux vector or in the estimation of the actual value of the speed. The current paper derives the discrete equations of different flux and speed estimator algorithms by using Tustin approximation. The performance of the algorithms, both in open and closed loop, is demonstrated via numerical simulation using a high speed motor drive with a low sampling to fundamental frequency ratio

Active and Reactive Power Distribution among multiple DFIG WTSS in an isolated microgrid

Wind energy sector is a well-researched field since depletion of fossil sources and environmental pollution issues led to the popularization of renewables. Many efforts have been made to optimise its power production and to minimize its losses. In case of m different sized power plants, due to different MPPs, if the demand is below the sum of their maximum power production at the given wind speed, it is highly likely that the optimal distribution will not be exact. There are several possibilities, one of them is to share the demand equally among them etc. The distribution of active and reactive powers will have an effect on each other and thus the optimal solution

Development of e-Learning Modules for Teaching Energy for Sustainable World

Within the project ”Teaching Energy for Sustainable World” (SustEner) financed by the European Union nine practically oriented modules with remote experiments or interactive animation materials will be offered in a web based learning portal. Here the development and the operation of two modules titled ”Solar Powered Electric Vehicles” and ”Luminous Efficacy of Modern Light Sources” are described in some detail