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© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. With the aim to increase standardization, reduce the cost, and obtain advanced performance features, the design of voltage-source power converter legs can be undertaken by combining several instances of a standard switching cell, properly connected in active neutral-point-clamped structures to reach the desired voltage and current ratings. These switching cells can be organized into switching-cell arrays. This design approach introduces several degrees of freedom into the design. Namely, the different options to interconnect the cells and the distribution of switching losses among these cells. This article aims to define an optimization problem to explore this design space. The design problem is formulated in different scenarios, involving different conversion configurations (dc-dc and dc-ac), different leg number of levels (two and three), and different types of available cells (standard and conduction-optimized in combination with switching-optimized). A weighted objective function is then defined in terms of leg simplicity, efficiency, and reliability. The value of the design variables that minimize the objective function with different sets of weighting factors are obtained under selected scenarios and operating conditions, to illustrate the flexibility of the converter design approach under study. The solution of the optimization problem is obtained using a surrogate optimization algorithm in MATLAB, well suited to quickly solve optimization problems involving a combination of integer design variables (the number of parallel switching cells in each converter leg position) and continuous design variables (the proportion of switching losses taken by each cell), together with linear and nonlinear constraints.

This paper deals with generic design and implementation of multi-cell multi-level multi-phase voltage source inverters. Based on a well-known topology, the paper focuses on place and route design to enable V and/or I scalability while ensuring high performance and high power densities. The topology is studied to define how conversion cells should be designed to ease and automate scalability in I and V. A prototype is built and tested, and the performances are benchmarked

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Predictive current control is applied to a wind energy conversion system implemented with a permanent-magnet synchronous generator connected to the grid through a back-toback neutral-point-clamped converter. This control approach allows to work in steady-state and to fulfill the low-voltage ride through requirements demanded by the power system operators.Dc-link neutral point voltage balance is also achieved by means of the predictive control algorithm.

Prize Letter Award, atorgat per la IEEE Power Electronics Society This letter introduces a new series of multilevel (ML) converters based on the ML clamping concept. By applying this technique, a ML clamping unit (MCU) conveys additional levels for synthesizing the output waveforms of a diode-clampedML dc– ac power converter. The basic building block of the ML clamping scheme is the ML clamping cell, which is composed of a pair of dc sources associated with one single-pole/triple-throw type of switch arrangement. The number of series-connected ML-clamping cells will set the number of levels of the synthesized waveform. By depending on the MCU arrangements, different converter configurations can be derived, namely, the common clamping and the modular types. Both approaches can be accomplished by employing classical three-level neutral-point-clamped (NPC) technology. Thus, the overall structure of the resultant converter is kept simple, wherein the number of parts count can be reduced, when compared with conventional NPC counterparts. In this letter, emphasis is given on the common clamping converter configuration. The attractiveness of the proposed ML concept is evidenced by conducting a comparative cost analysis. Experimental results are presented as a practicality proof of the proposed ML power converter. Peer Reviewed Award-winning

This work presents the development of the space vector pulse width modulation (SVPWM) of a new multi-level converter topology. First, the proposed converter and its natural space vector diagram are presented. Secondly, a modified space vector diagram based on the virtual-vectors technique is shown. Simulation results by using a space vector approach are presented. Special emphasis is given on the total harmonic distortion (THD) by making a comparison with those of the classical NPC topologies.

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Las topologías de convertidores multinivel han recibido una atención especial durante las dos últimas décadas debido a sus notables ventajas en aplicaciones de alta potencia y media/alta tensión. En estas topologías, y comparadas con el convertidor tradicional de dos niveles, el voltaje que soporta cada dispositivo semiconductor es menor, evitando los problemas asociados con la interconexión serie de dispositivos. La distorsión armónica en la tensión de salida es también menor y la eficiencia mayor. Pero incorporan un número superior de dispositivos semiconductores y la estrategia de modulación resultante es, por tanto, más compleja.Entre estas topologías, el convertidor cc-ca de tres niveles trifásico con conexión al punto neutro del bus de cc es probablemente el más popular. La aplicación a este convertidor de técnicas de modulación convencionales causa una oscilación de la tensión del punto neutro de baja frecuencia (tres veces la frecuencia fundamental de la tensión de salida). Esta oscilación, a su vez, supone un incremento del estrés de tensión de los dispositivos y provoca la aparición de armónicos de baja frecuencia en la tensión de salida.Esta tesis presenta una nueva técnica de modulación del pulso de conducción de los dispositivos semiconductores para convertidores de tres niveles trifásicos con conexión a punto neutro, capaz de conseguir un control completo de la tensión del punto neutro con una distorsión armónica reducida en la tensión de salida alrededor de la frecuencia de conmutación. Esta nueva técnica de modulación, basada en la definición de unos vectores espaciales virtuales, garantiza el equilibrado de la tensión del punto neutro con cualquier carga (lineal o no, cualquier factor de potencia) y para todo el rango de tensión de salida, con el único requisito de que la suma de corrientes de fase sea nula.Las características de la técnica de modulación propuesta y sus beneficios con respecto a otras modulaciones se han verificado a través de simulaciones y experimentos tanto en lazo abierto como en lazo cerrado., Multilevel converter topologies have received special attention during the last two decades due to their significant advantages in high-power medium- and high-voltage applications. In these topologies, and compared to the previous two-level case, the voltage across each semiconductor is reduced, avoiding the problems of the series interconnection of devices. The harmonic distortion of the output voltage is also diminished and the converter efficiency increases. But a larger number of semiconductors is needed and the modulation strategy to control them becomes more complex.Among these topologies, the three-level three-phase neutral-point-clamped voltage source inverter is probably the most popular. The application of traditional modulation techniques to this converter causes a low frequency (three times the fundamental frequency of the output voltage) oscillation of the neutral-point voltage. This, in turn, increases the voltage stress on the devices and generates low-order harmonics in the output voltage.This thesis presents a novel pulsewidth modulation for the three-level three-phase neutral-point-clamped converter, able to achieve a complete control of the neutral-point voltage while also having a low output voltage distortion at around the switching frequency. The new modulation, based on a virtual space vector concept, guarantees the balancing of the neutral-point voltage for any load (linear or nonlinear, any load power factor) over the full range of converter output voltage, the only requirement being that the addition of the output three-phase currents equals zero.The performance of this modulation approach and its benefits over other previously proposed solutions are verified through simulation and experiments in both open- and closed-loop converter configurations.