Omar Fernando Ruiz-Martinez

The microbiological safety of milk can be ensured through heat processing; however, this method has a negative effect on the sensory profile of this food product. Emerging technologies could be used as an alternative process for guaranteeing innocuity and maintaining sensory changes. An alternative is to evaluate pulsed electric field (PEF) electroporation, which is a method of processing cells using short pulses of a strong electric field. PEF has the potential to be a type of alternative low-temperature pasteurization process that consists of high-frequency voltage pulsations. Specifically, the presented work is a proof of concept for the design of a converter capable of generating a PEF to feed a load that meets the impedance characteristics of milk. The proposed converter is simulated using PLECS software (4.9.6 version) under impedance change scenarios that emulate variations in milk throughout the entire process. This research proposes the modification of a classic Vienna rectifier (adding an MBC—Multilevel Boost Converter structure) to supply a pulsating signal that could be used for low-temperature processes of milk to guarantee proper pasteurization. The characteristics of the generated high-voltage pulse make it feasible to quickly process the real sample. The control law design considers a regulation loop to achieve a voltage in the range of kV and a switching-type control law that activates switches in MMC arrays. These switches are activated randomly to avoid transients that cause significant stress on them.

Fractional calculus (or arbitrary order calculus) refers to the integration and derivative operators of an order different than one and was developed in 1695. They have been widely used to study dynamical systems, especially chaotic systems, as the use of arbitrary-order operators broke the milestone of restricting autonomous continuous systems of order three to obtain chaotic behavior and triggered the study of fractional chaotic systems. In this paper, we study the chaotic behavior in fractional systems in more detail and characterize the geometric variations that the dynamics of the system undergo when using arbitrary-order operators by asking the following question: is the Lyapunov exponent sufficient to describe the dynamical variations in a chaotic system of fractional order? By quantifying the convex envelope generated by the 2D projection of the system into all its phase portraits, the changes in the area of the system, as well as the volume of the attractor, are characterized. The results are compared with standard metrics for the study of chaotic systems, such as the Kaplan–Yorke dimension and the fractal dimension, and we also evaluate the frequency fluctuations in the dynamical response. It is found that our methodology can better describe the changes occurring in the systems, while the traditional dimensions are limited to confirming chaotic behaviors; meanwhile, the frequency spectrum hardly changes. The results deepen the study of fractional-order chaotic systems, contribute to understanding the implications and effects observed in the dynamics of the systems, and provide a reference framework for decision-making when using arbitrary-order operators to model dynamical systems.

This work introduces a boost converter with quadratic gain. Its main advantage compared to well-known similar quadratic boost converters is that it requires capacitors with a relatively small capacitance and inductors with small inductance, leading to a reduction in the size or stored energy while performing a power conversion of similar power rating and the same switching ripples in both the input current and the output voltage. It is inspired by the recently introduced ISB converter and uses a specific PWM method. This results in achieving switching ripple constraints while using smaller energy storage elements (capacitors and inductors). The updated converter offers the same voltage gain compared to the conventional quadratic boost topology with the benefit of compact component sizes. While it has more passive elements, they are of reduced size. An analysis of energy storage revealed that this new converter uses only half the energy in inductors and 14% in capacitors when compared to specific design parameters.

The boost converter is mostly used as a DC–DC converter, but two boost converter power stages can be configured to perform the DC–AC conversion. In this case, the control system of the power stage must be designed for trajectory tracking (instead of regulation), which brings interesting challenges. This work deals with the design of a higher-order sliding mode output regulator for a DC-biased sinusoidal power conversion problem on a single boost converter stage of a boost inverter for asymptotic trajectory tracking of the voltage capacitor. The steady-state reference signal for the inductor current is proposed as an approximated solution of the well-known Francis–Isidori–Byrnes equations. The used approach is the direct control of the output, where the nonminimum phase variable, i.e., an adequate sliding function, stabilizes the current through the inductor. Lastly, by means of real-time experimentation, the good performance of the proposed control strategy is verified.

Onboard charging systems (OBCs) convert AC power from an external charging source into a DC voltage used to charge the battery pack of an electric vehicle (EV). OBCs are versatile since they can convert energy from almost every AC source, including standard household electrical receptacles, without needing wall chargers or charging stations. Since the same motor-drive electronics are reconfigured for onboard charging, weight and cost barely increase. However, the power quality and reliability of the OBCs are essential elements for proper grid interconnection. This article reviews the failures of power electronic converters that can be used for onboard charging and their most prominent fault-tolerance techniques. The various fault-tolerance methods are evaluated and compared in terms of complexity, cost, and performance to provide insights for future developments and research directions.

Paralleled boost asymmetric configurations operating in discontinuous conduction mode (DCM) are suitable for integrating dissimilar green energy generating sources and control algorithms in versatile scenarios where voltage step-up, low cost, stable operation, low output ripple, uncomplicated design, and acceptable efficiency are needed. Unfortunately, research has mainly been conducted on the buck, sepic, switched-capacitor, among other asymmetric configurations operating in continuous conduction mode (CCM), to the authors’ knowledge. For asymmetric boost type topologies, achieving simultaneous CCM is not a trivial task, and other problems such as circulating currents arise. Research for interleaved converters cannot be easily extended to asymmetric boost topologies due to the dissimilarity of control algorithms and types of sources and parallel stages. This paper analytically establishes properties of stability, output ripple, output voltage, and design for asymmetrical paralleled boost converters operating in DCM with simultaneous or phase delayed (sequential) triggering. A 300 W experimental design and the respective tests allow validation of such properties, resulting in an easy-to-implement configuration with acceptable efficiency.

This paper contains a novel approach to DC-DC converter nonlinear control design, working on continuous conduction mode (CCM). In particular, the problem of instability induced by constant power loads (CPLs) is addressed. The proposed setting is based on the use of lifted models in terms of power and energy, obtained from voltage/current observable nonlinear transformations. We show that stability can be imposed on lifted models via control design, in a much more direct fashion than in traditional current/voltage coordinates. To illustrate the versatility of this approach, we propose three different nonlinear controllers with stabilization capabilities, that exploit the advantages of lifted dynamics in a different way. These strategies are experimentally validated and tested under abrupt and intermittent input-voltage and load variations.

This work presents a power-electronics based system for renewable energy applications, the system is driven with an only one switch quadratic type boost converter, the discussed converter is based on a stack of switching stages which provide a large voltage gain, a desirable feature for fuel cell generation systems, the converters gain function is the quadratic boost-type converters; furthermore, the topology can be extended. The major benefit of the topology is that there is not a capacitor that sustains the entire output voltage, in contrast to other similar topologies in which there is a capacitor rated to the output port voltage, there is no high voltage capacitor in this system. Experimental verification is presented to confirm the system principles; experiments included a fuel cell emulator that was built and used for the experiments.

This study proposes a non‐isolated quadratic boost converter (QBC) that features a low‐output‐voltage ripple with respect to traditional QBCs. This advantage is in contrast with other topologies that require a higher amount of stored energy by capacitors to achieve the same output‐voltage ripple specification. This benefit permits to design a compact converter, since the size of capacitors is proportional to their energy storage rating. Moreover, the proposed transformerless topology is suitable for applications that require high‐voltage gains as in the case of renewable energy applications. The main properties of the converter are corroborated as well as its advantages by providing mathematical models, analytical waveforms and experiments.