Upravljanje asimetričnim inverterom ujednačenog koraka s 13 razina korištenjem optimizacije roja čestica

Harmonic Elimination Strategy (HES) has been a widely researched alternative to traditional PWM techniques. This paper presents the harmonic elimination strategy of a Uniform Step Asymmetrical Multilevel Inverter (USAMI) using Particle Swarm Optimization (PSO) which eliminates specified higher order harmonics while maintaining the required fundamental voltage. This method can be applied to USAMI with any number of levels. As an example, in this paper a 13-level USAMI is considered and the optimum switching angles are calculated to eliminate the 5th, 7th, 11th, 13th and 17th harmonics. The HES-PSO approach is compared to the well-known Sinusoidal Pulse-Width Modulation (SPWM) strategy. Simulation results demonstrate the better performances and technical advantages of the HES-PSO controller in feeding an asynchronous machine. Indeed, the harmonic distortions are efficiently cancelled providing thus an optimized control signal for the asynchronous machine. Moreover, the technique presented here substantially reduces the torque undulations.Strategija eliminacije harmonika je dobro istražena alternativa tradicionalnoj pulso-širinskoj modulaciji. U ovom radu opisana je strategija eliminacije harmonika asimetričnog višerazinskog invertera ujednačenog koraka uz korištenje optimizacije roja čestica čime se eliminiraju harmonici višeg reda uz zadržavanje fundamentalnog napona. Takva metoda može se primijeniti neovisno o broju razina invertera. Kao primjer korišten je inverter s 13 razina kod kojeg se eliminiraju peti, sedmi, jedanaesti, trinaesti i sedamnaesti harmonik. Predloženo rješenje uspoređeno je s dobro poznatom sinusnom pulsno-širinskom modulacijom. Simulacijski rezultati pokazuju prednosti predloženog rješenja. Harmonička distorzija je uspješno poništena te je upravljački signal za asinkroni stroj optimalan. Štoviše, predložena tehnika znatno smanjuje promjene momenta

Asymmetrical multilevel inverter for large induction machine drives

This paper describes some techniques to improve the output waveform quality of multilevel inverts fed-indction machines. The investigated topologies are the diode-clamped and series-connection of H-bridges. Thesetechinques are based on an unequal dc-voltage supplyng. The multicarrier-based pulse width modulation techniques applied to the control of these inverters is also investigated

Multilevel Inverter for Power System Applications : Highlighting Asymmetric Design Effects form a Supply Network Point of View

This paper highlights some effects of an asymmetrical design on three phase multilevel inverters from a supply network point of view. The investigated topology is based on a series connection of single phase inverters (partial cell) in each phase. Each partial cell is fed through a three-phase diode rectifier for a unidirectional power flow, fed itself through the secondary of the power transformer (PT). From analytical relationships in continuous and discontinuous current conduction mode, it’s shown that a symmetrical multilevel inverter has a smaller total harmonic distortion than an asymmetrical multilevel inverter (AMI) with the same number of partial cells per phase. An AMI is not more interesting than a classical three phase inverter. The total harmonic distortion of an AMI is compatible to the recommended IEEE std 519-1992 for all feeding possibilities for a given number of partial cells per phase. In order to exploit the main advantages of an asymmetrical design from a load point of view (generation of a high resolution voltage phasor, reduction of the number of power devices for the same resolution, flexibility for the dc-voltage feeding choice), a new solution is investigated : A symmetrical PT feeds an AMI

Convertisseurs multiniveaux asymétriques pour des applications de moyenne et forte puissance

Cet article traite des convertisseurs multiniveaux triphasés dont la topologie est basée sur la mise en série d’onduleurs partiels par phase. Généralement, les tensions continues alimentant les onduleurs partiels sont supposées être identiques ou distribuées sous forme de suite géométrique de raison deux ou trois ; le nombre de réalisations possibles avec des nombres de niveaux différents reste limité. Dans cet article, nous proposons une approche générale basée sur une résolution de simples inéquations algébriques, permettant ainsi d’incrémenter le nombre de possibilités d’utilisation du convertisseur sans ajouter une complexité aux circuits de puissance et de commande. Une nouvelle terminologie y est proposée, et les résultats des simulations attestent de la fiabilité des relations analytiques établies

A Generalized Design Principle of a Uniform Step Asymmetrical Multilevel Converter For High Power Conversion

This paper is focused on a general design principle of a uniform step multilevel converter, with K series-connected full bridges inverters per phase. A new design terminology is proposed and analytical relationships are established. The DC-voltage sources supplying partial inverters are supposed to be rationally unbalanced. The corresponding “Asymmetrical” topology provides more flexibility to the designer, and can generate a large number of levels (any odd number from 2K+1 to 3K) without increasing the number of H-bridges. Simulation results and experimental tests shown the reliability of the design approach suggested

Re-generative Asymmetrical Multi-level Converter for Multi-Megawatt Variable Speed Drives

This paper is focused on the design, modulation and control of a re-generative non-symmetrical multi-level converter for high-power applications such as oil and gas or mining. The converter is based on standard IGBT modules and the DC-link voltages are chosen in order to be easily implemented for real industrial motor drives. The modularity of the suggested topology can help to drive up to 60 MW using PWM strategies in normal mode of operation. The output voltage has 23 levels, enabling nearly no torque ripple and avoiding to use an output sine filter. A new control strategy is suggested to reduce power-switch losses and to increase the availability of the proposed converter

Model reduction of electric rotors subjected to PWM excitation for structural dynamics design

International audienceRotors of asynchronous machines can be subjected to risk of failure due to vibratory fatigue. This is caused by the way electric motors are powered. Pulse Width Modulation (PWM) is the control strategy of the traction chain. This signal is composed by a fundamental and numerous harmonics of voltage and current that induce harmonics onthe torquesignal resultingin hugetorque oscillations. It canlead to repeated torsionalresonance when coincidences occur. This can induce severe damages and even lead to rupture if electric excitations are not taken into account at the design stage. In this work, a magnetic finite element model is built by using Fourier decomposition in order to take into account harmonics due to PWM. Pressures exported from this model are used as inputs for mechanical FEM. A mechanical reduced order model is also proposed in order to compute stress in rotating part. This second model allows to reduce time computation and then to consider several operating points to build a complete speed up. A correlation is performed between these two models and rotating tests in order to discuss the relevance of these approaches to design rotor parts