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This paper presents a new modulation concept for three-to-single-phase direct AC/AC modular multi-level converter-based railway interties. The concept minimizes the inherent harmonic coupling between the two grid sides and is therefore particularly suited to operation at very low cell numbers and switching frequencies. Moreover, it facilitates the use of specific modulation methods, such as optimized...
The international standardization community is currently reviewing the harmonic distortion limits in the frequency range 2 to 150 kHz, referred to as supraharmonics. Power electronics has emerged as a ubiquitous technology, which also plays a critical role in this subject. Broadly speaking, the reduction of emission in the lower-frequency ranges appears to result in an increase in supraharmonic emission...
Multilevel converters (MCs) are utilized in medium voltage (MV) high power applications due to its higher efficiency than two level converters. On the other hand, modular multilevel converters (MMCs) provide several advantages with regard to other MCs, such as higher scalability, reliability and no requirement of a common DC capacitor. Particularly, low switching frequency modulations, such as (2N+1)...
In this paper, a Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) method, which utilizes adjustable dc links, is presented for a Static Synchronous Compensator (STATCOM) based on Cascaded H-Bridge (CHB) multilevel converter. The proposed switching algorithm is able to fix the capacitors voltages at optimum and unequal values, while injecting the desired reactive power, in order to eliminate...
This paper summarizes the state of part of the discussions in CIGRE/CIRED/IEEE joined working group C4.24, especially where it concerns supraharmonics. There is an increasing interest from the international smart grid standard-setting community in knowledge about harmonics distortion in the frequency range 2 to 150 kHz, referred to as supraharmonics. The paper presents measurements of waveform distortion...
This paper describes an enhanced control technique to improve the output current quality of a multilevel current-source inverter operating at both high- and light-load conditions. The new technique, named here as RS-PWM, combines the simple control of redundant-switching methods with more flexible PWM methods and has been shown in this study to be superior to both. The results have been validated...
In the present work Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) based on Particle Swarm Optimization is proposed for the enhancement of the H-Bridge multilevel inverter output voltage quality. The problem of the SHE-PWM is presented by a constrained nonlinear objective function which has to be minimized. The main aim is the calculation of the switching angles vector solution representing...
Multilevel converters feature a staircase output voltage, resulting in a lower number of switching operations and better spectral characteristics. Switching every element only once a load cycle (fundamental frequency switching), losses can be minimized. By calculating optimum switching angles, the emergence of lower harmonics can be avoided. Derived from conventional space vector modulation (SVPWM),...
Multilevel converters are used in high power and high voltage applications due to their attractive benefits in generating high quality output voltage. Increasing the number of voltage levels can lead to a reduction in lower order harmonics. Various modulation and control techniques are introduced for multilevel converters like Space Vector Modulation (SVM), Sinusoidal Pulse Width Modulation (SPWM)...
A strategy is presented for the control of a 4-limb flying-capacitor multi-level inverter (FCMI) as an active power filter for unbalanced load conditions. Improved reference tracking is achieved using a modified deadbeat controller, and a naturally-balanced 3DPWM technique enables sensor-less flying-capacitor voltage control. Simulation results show the effectiveness of the proposed scheme.
A modified Third Harmonic Injection PWM (THI-PWM) modulator that reduces output harmonics has been presented in this paper. The modulator is combined with harmonic injection and phase shifting parts in Simulink design. The harmonic injection ratios have been analysed according to harmonic amplitude ratio of third harmonic to fundamental amplitude. The designed modulator is capable to minimize the...
Multilevel inverters supplied from equal and constant dc sources almost donpsilat exist in practical applications. The variation of the dc sources affects the values of the switching angles required for each specific harmonic profile, as well as increases the difficulty of the harmonic eliminationpsilas equations. This paper presents an extremely fast optimal solution of harmonic elimination of multilevel...
Estimation of optimum switching angles for multilevel converters so as to produce the required fundamental voltage while at the same time eliminate specified lower order harmonics through Artificial Neural Networks (ANNs) is presented. The proposed technique uses the best performance solutions (lowest THD solutions) as the training data set for proposed ANN system. This technique can be applied to...
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