Active Power-Decoupling Methods for Photovoltaic-Connected Applications: An Overview

This study compares ripple port, stacked switched capacitor, and capacitive energy storage architectures for active power decoupling, comparing the number of components, performance, energy density, DC-link capacitor reduction, efficiency, and frequency operation to highlight their main benefits and drawbacks for single-phase grid-connected applications. The overview reveals equivalent effective energy density without electrolytic capacitors, as well as enhanced simplicity, performance, and durability, thereby providing stacked switched capacitors as an attractive power-decoupling alternative for multi-stage connected applications, based on the principle that its individual buffer capacitors absorb and deliver energy without tightly constraining their individual terminal voltages, while maintaining a narrow range voltage at the buffer DC port

CÁLCULO DE LOS ÁNGULOS ÓPTIMOS DE CONMUTACIÓN PARA UN INVERSOR MULTINIVEL UTILIZANDO EVOLUCIÓN DIFERENCIAL (CALCULATION OF OPTIMAL SWITCHING ANGLES FOR A MULTILEVEL INVERTER USING DIFFERENTIAL EVOLUTION)

Resumen Actualmente en varios trabajos de investigación se han utilizado los métodos metaheurísticos para minimizar de forma efectiva la distorsión armónica total (THD, Total Harmonic Distortion) en inversores multinivel, ya que estos proporcionan tiempo de cálculo y resultados efectivos. Dentro de estos métodos la evolución diferencial ha sido el algoritmo que en recientes años se ha implementado para la reducción de la THD. Este trabajo presenta el algoritmo de Evolución Diferencial (ED) para encontrar los ángulos de conmutación óptimos en un inversor multinivel en cascada de siete niveles para eliminar los armónicos de orden inferior. Los armónicos impares de orden inferior no pueden eliminarse fácilmente, ya que contienen ecuaciones no lineales trascendentales, resultantes de la serie de Fourier. Las soluciones a estas ecuaciones son complicadas y requieren mucho tiempo. También este trabajo se centra en la búsqueda de los parámetros iniciales del algoritmo de Evolución Diferencial para observar cual combinación se desempeña mejor, tanto en rapidez como fiabilidad para encontrar una THD mínima casi óptima. Además, realizó una simulación de un inversor multinivel en cascada de siete niveles con carga RL en Simulink para validar los resultados, además de realizar diferentes iteraciones variando los parámetros para así verificar cuál de estos proporciona una mejor búsqueda de los ángulos de conmutación, además de brindar una discusión de los resultados obtenidos. Palabras Clave: Evolución Diferencial, Inversor Multinivel, Métodos metaheurísticos, Reducción de THD. Abstract In different research papers, metaheuristic methods have been used to effectively minimize the Total Harmonic Distortion (THD) in multilevel inverters, since they provide calculation time and effective results. Among these methods, differential evolution has been the algorithm that has been implemented in recent years for THD reduction. This paper presents the Differential Evolution (DE) algorithm to find the optimal switching angles in a seven-level cascaded multilevel inverter to eliminate the lower order harmonics. The lower-order odd harmonics cannot be easily eliminated, as they contain transcendental non-linear equations, resulting from the Fourier series. The solutions to these equations are complicated and time consuming. Also, this work focuses on finding the initial parameters of the Differential Evolution algorithm to observe which combination performs best, both in speed and reliability to find a near-optimal minimum THD. It also performed a simulation of a seven-level cascaded multilevel inverter with RL load in Simulink to validate the results, in addition to performing different iterations varying the parameters to verify which of these provides a better search of the switching angles, in addition to providing a discussion of the results obtained. Keywords: Differential Evolution, Metaheuristic Methods, Multilevel Inverter, THD Reduction

Modification of SPWM Modulating Signals for Energy Balancing Purposes

There is currently a growing interest in efficient power generation and transformation without increasing the cost and complexity of a system. One type of transformation is the conversion of energy from a direct current to an alternating current, which is used in various applications, for example, in photovoltaic systems. One of the elementary components of these systems is the inverter. However, there are several drawbacks in the design of these systems, such as the energy balance between their semiconductor devices. Therefore, it is important to study alternatives to balance the energy and thus achieve a positive impact on both the economic and reliability aspects of the system. This article deals with the study, design, and implementation of the modification of a modulation technique with reconstructed modulating signals, which aims to ensure the energy balance in each cell of a multilevel inverter and, at the same time, present better results concerning the different parameters of comparison established, such as harmonic distortion, percentage of unbalance, percentage of use of digital resources, and power transferred to the load

On the State-Feedback Controller Design for Polynomial Linear Parameter-Varying Systems with Pole Placement within Linear Matrix Inequality Regions

The present paper addresses linear parameter-varying systems with high-order time-varying parameter dependency known as polynomial LPV systems and their controller design. Throughout this work, a procedure ensuring a state-feedback controller from a parameterized linear matrix inequality (PLMI) solution is presented. As the main contribution of this paper, the controller is designed by considering the time-varying parameter rate as a tuning parameter with a continuous control gain in such a way that the closed-loop eigenvalues lie in a complex plane subset, with high-order time-varying parameters defining the system dynamics. Simulation results are presented, aiming to show the effectiveness of the proposed controller design