Author: Ibraheem Mohammed Khalil

One of most important challenge that face industrial electronics is to enhance the performance of converters used switching device. This paper gives a sufficient method to reduce total harmonic distortion for super- multiple of supply frequency based on converting (50) Hz to (400) Hz, this method depends upon comb filter technique, by shifting the main supply by suitable two angles phase shift using two phase shifting transformers and applying these sources to three converters to create three distorted ( 400) Hz waveforms each one have different displacement angle, three waveforms added to gather in order to create new 400Hz has low distorted waveform, applying this method will reduce the THD from 70% to 36 %.  

his paper proposed a new frequency changer which generates high power frequency by exploiting the principle of discrete amplitude modulation. This converter is capable of converting the three-phase 50Hz, public supply to appropriately balanced 3 three-phase supply with output frequency higher than the input supply frequency. The frequency changing is achieved by generating and mixing two or more amplitude modulated voltage waves using bidirectional power transistors in the modulating circuit. By appropriate selection of the modulation indices and phase shifting between the supply voltages, the supply frequency component is entirely suppressed. The harmonic content of the resulting voltage waveforms are found to be very low compared with that of the conventional ac–to–ac converters such as cycloconvertesrs and cyclo-inverters. The proposed converter has the features of relatively low cost, simplicity, and high reliability. https://www.researchgate.net/profile/Mohammed_Khesbak/publication/269763760_A_Super_-_Multiple_of_Supply_frequency_Converter_Based_on_Discrete_Amplitude_Modulation/links/5495d9290cf20f487d2f5839.pdf

Direct AC to AC power conversion was always a challenge to be proposed as an alternative for the DC-link one. This is due to multiple of reasons such as less complexity, power regeneration, and unity power factor privileges. However, the challenge is represented by producing a direct AC to AC system with output waveforms having reduced total harmonic distortion comparable or superior to that generated by the DC-link converters. In such a trend this paper introduces an enhanced AC-to-AC frequency changer with reduced total harmonic distortion frequency spectrum compared to the envelope cycloconverter one. This proposed work introduces smart comparative phases switching carried out via a processing unit that detects and measure the analogue voltages of each phase and sends a switching triggers to the power switching circuit. The proposed work reflected an effective reduction in output waveforms harmonic content (about 60%) compared to the envelope cycloconverter with low cost system requirements. http://www.jee.ro/index.php/jee/article/download/WR1415650386W54611c522ca87/1189

AC to AC frequency converters had a challenge to be proposed as a reduction of THD. This challenge due to eliminate the most effective harmonics in frequency spectrum with low cost and no difficulty. However, the challenge is represented by producing new technique for AC to AC frequency changer with lower total harmonic distortion compared with regular AC to AC frequency changer. This proposed work introduces reduction based on eliminate the 3rd predominant harmonic by imposing a waveform with same frequency, amplitude and poly phase of presented harmful harmonic the elimination for the most effective harmonic will cause reduction in THD. The proposed technique gave a significant reduction in THD (about 52%) with respect to regular AC to AC frequency changer with low cost implementation requirements. https://www.researchgate.net/profile/Ibraheem-Khalil-2/publication/316906459_Ac_to_Ac_Frequency_Changer_THD_Reduction_Based_on_Selective_Harmonic_Elimination/links/592c3a700f7e9b9979ae8bad/Ac-to-Ac-Frequency-Changer-THD-Reduction-Based-on-Selective-Harmonic-Elimination.pdf

Due to the vitality of the SPWM technique in industry of the power conversion devices, this paper suggests a new harmonic distortion minimization technique so far called multi-tone SPWM. This proposed technique aims to inject the modulating waveform with a high frequency component at the low voltage regions (edges of the waveform) to increase number of switching pulses at these regions and hence increase power content of the fundamental component of the output spectrum based on a power redistribution concept. Optimization process was accomplished on the technique key parameters and a considerable of a 21% reduction was achieved in THD% compared with the traditional unipolar SPWM technique. https://www.atlantis-press.com/article/25875764.pdf