Oswaldo Lopez-Santos

Universitat Rovira i Virgili | URV · Department of Electronic, Electrical and Automatic Engineering (DEEEA)

This paper presents a two-level hierarchical control method for the power distribution between the hybrid energy storage system (HESS) and the main dc bus of a microgrid for ultrafast charging of electric vehicles (EVs). The HESS is composed of a supercapacitor and a battery and is an essential part to fulfill the charging demand of EVs in a microg...

A critical reduction in the total harmonic distortion in the output voltage of multilevel inverters can be obtained with an appropriate selection of the angles to switch the power semiconductors at low frequency. Among the methods used to obtain the required sequence of angles, it is possible to recognize both standard and optimized methods, like t...

Modern DC-DC power conversion represents an important challenge because connected loads are not purely resistive as it has been conventionally considered. Furthermore, the corresponding power converters perform functions which are not limited to regulate either a specific output voltage or output current. One of these new functions is the transfer...

This report proposes the electrical architecture of an ultrafast charging station for electric vehicles (EVs), which is based on a hybrid energy distribution system made up of an AC bus and two DC buses, each one of different voltage. The proposal is the result of a Montecarlo’s statistical analysis of real traffic data that leads to estimate the p...

Selecting the converter in the output stage of an ultrafast charging system for electric vehicles (EVs) has to take into account different constraints imposed by the number of charging ports and the type of power distribution (AC, DC or both). This paper discusses qualitative criteria for selecting the most appropriate converter for a given electri...

The increasing demand for energy and the high penetration of distributed energy resources require the evolution of current electrical systems toward smarter and more reliable electric grids. In this regard, microgrids (MG) play a vital role in integrating distributed energy resources (DER), loads, and storage systems. However, microgrid architectur...

This report proposes the electrical architecture of an ultrafast charging station for electric vehicles (EVs), which is based on a hybrid energy distribution system made up of an AC bus and two DC buses, each one of different voltage. The proposal is the result of a Montecarlo’s statistical analysis of real traffic data that leads to estimate the p...

This paper introduces a method for the reconfiguration of a transformer-based cascaded multilevel inverter (CT-MLI), which allows the use of alternative switching patterns when individual inverter stages cease to operate as a result of a failure in the circuit switches. Different possibilities of reconfiguration of the inverter stages to provide th...

The increasing interest in renewable energy sources has brought attention to large voltage-gain dc–dc converters; among the different available solutions to perform a large voltage-gain conversion, this article presents an overview of non-isolated dc–dc converter topologies that utilize switched-capacitor circuits, i.e., diode-capacitors voltage mu...

This paper reports the development of a model for continuous simulation of the power flow into AC–DC hybrid microgrids operating for different generation–consumption scenarios. The proposed application was assembled using a multiple-input multiple-output model which was built using blocks containing simplified models of photovoltaic (PV) modules, w...

This special issue contributes theoretical and practical advances to the state-of-the-art field at the crossroads of power electronics and control systems. The seven included papers cover particular applications requiring either DC–DC, DC–AC or AC–DC conversion stages.

The low energy storage quadratic boost converter (LES-QBC) was recently proposed as an advantageous topology in terms of reduced output voltage ripple and fast dynamic response, besides high power density and reduced energy storage. The topological configuration can be exploited mainly through a 180 phase shift between the controlled switch gate si...

This paper extends the results recently proposed in Part I of this research work focused on the stabilization of power electronic converters. This second part is devoted to cases in which the underlying control problems can be translated into tracking control problems. This is the case for DC-AC converters whose output must track a sinusoidal refer...

The use of power converters has grown in the last years with the advances in photovoltaic and wind based power generation systems, and the progress in modern concepts such as microgrids and electric mobility. A consequence has been the development of devices allowing for the exchange of energy among different distribution buses, and feeding AC or D...

This work deals with the control of power electronics converters. In that context, the majority of the problems of interest can be translated into two main problems: stabilization control problems and tracking control problems. Numerous methods exist in the literature to propose solutions which are based on several ways of handling them in a more a...

This chapter illustrates the use of hysteresis control techniques applied to multilevel inverters. First, a general classification of different methods applied to control multilevel inverters is presented from three main points of view: that of the switching frequency (fundamental frequency and high frequency), the related application (grid-tie and...

Nonlinear phenomena in the dynamic behavior of DC motors are commonly disregarded in speed regulation systems because it has a constant operation point or a reduced range of variation. Therefore, in the majority of applications, a second order linear model is enough to design the required controllers. However, in angle positioning systems involving...

Sliding-mode control (SMC) has been successfully applied to boost inverters, which solves the tracking problem of imposing sinusoidal behavior to the output voltage despite the coupled or decoupled operation of both boost cells in the converter. Most of the results reported in the literature were obtained using the conventional cascade-control stru...

This paper proposes a non-isolated quadratic boost converter that features a low output voltage ripple with respect to traditional quadratic boost converters. 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 t...

Detection of an environmental contaminant requires the use of expensive measurement equipment, which limits the realization of in situ tests because of their high cost, their limited portability, or the extended time duration of the tests. This paper presents in detail the development of a portable low-cost spectrophotometer which, by using a speci...

Dear Colleagues, Your contribution to the Special Issue "Control of Power Electronic Converters Special Issue" in the Journal "Applied Sciences" are welcome. The aim of this special issue is to provide a means of interaction between power electronics and control specialist communities which compile the state of the progress in the control of powe...

DC–DC interlinking converters (ILCs) allow bidirectional energy exchange between DC buses of different voltage levels in microgrids. This paper introduces a multimode control approach of a half-bridge DC–DC converter interlinking an extra-low-voltage DC (ELVDC) bus of 48 VDC and a low-voltage DC (LVDC) bus of 240 VDC within a hybrid microgrid. By u...

This paper presents a strategy to control the dynamic power sharing in a hybrid energy-storage system (HESS). The HESS is composed of a battery array of 24 V, a supercapacitor module of 16 V and 2 DC-DC converters allowing the connection of the system to an extra low voltage DC (ELVDC) bus of 48 V within a hybrid microgrid. The proposed strategy co...

Cascade transformer multilevel inverters (CT-MLI) are DC–AC converters used in medium and high power applications to provide standardized AC output. Despite their numerous advantages and robustness, these devices are highly susceptible to fault events because of their high amount of components. Therefore, early failure detection enables turning off...

This paper deals with the analysis and design of a sliding mode-based controller to obtain high power factor (HPF) in the bridgeless isolated version of the single ended primary inductor converter (SEPIC) operating as a single-phase rectifier. In the work reported here, the converter is used as a unidirectional isolated interface between an AC sour...

This paper introduces a method to enforce balanced power distribution between the stages of a single-phase transformer-based cascaded multilevel inverter using the new asymmetric ratio 6:7:8:9 between stages. Since the inverter is fed by a single DC source, asymmetry is enforced by means of the transformer turns ratio providing multiple redundant s...

This paper introduces a method to enforce balanced power distribution between the stages of a single-phase transformer-based cascaded multilevel inverter using the new asymmetric ratio 6:7:8:9 between stages. Since the inverter is fed by a single DC source, asymmetry is enforced by means of the transformer turns ratio providing multiple redundant s...

This paper deals with the control of the full-bridge inverter using bipolar and unipolar strategies. This problem is rigorously formulated as a sinusoidal reference tracking problem, the reference being generated by an appropriate exosystem. A unified model of the inverter for the two strategies is first derived, and then, the problem is translated...

This paper introduces a maximum power point tracking (MPPT) method based on a power (P) versus static conductance (G) curve of a photovoltaic (PV) array. The maximum power point (MPP) is tracked by comparing the PV array instantaneous power to a varying power reference generated by the MPPT algorithm. The comparison error is used to reduce or incre...

This brief presents a control law based on a hybrid dynamical systems theory for a dc-ac converter. This theory is very suited for an analysis of power electronic converters, since it combines continuous (voltages and currents) and discrete (on-off state of switches) signals avoiding, in this way, the use of averaged models. Here, practical stabili...

This paper presents the design and implementation of a low-cost spectrophotometer (LCSPM) for in-situ detection of mercury in water. The proposed device is composed of a white light emitting diode (LED), a diffraction grating (DG), a rotational positioning system, two photodiodes and a low-cost microcontroller. High-resolution angle displacement of...

A hold-up time extension circuit (HTEC) is used to charge and discharge an auxiliary capacitor. This capacitor stores the energy required to extend the operation time of critical loads experiencing short duration failures (SDF) at the DC bus to which they are connected. This paper presents complete modeling and a control-wise approach to a parallel...

This work describes in detail a computational tool designed to study performance indicators of a four-stage transformer-based single-phase cascaded multilevel inverter. The proposed system integrates simulation, on-line measurement, control and signal processing providing automating testing functionality to optimize the performance of the inverter...

This paper introduces a simplified method for digital generation of high-quality references required for control of single-phase grid-connected (GC) power converters, which can generate synchronized sinusoidal waveforms at the same frequency of the input signal or its harmonics. Therefore, its application can be useful for active power filtering, h...

This paper presents an event-triggered approach to optimally implement a Maximum Power Point Tracking (MPPT) algorithm into a Digital Signal Processor (DSP). The proposed method allows improving the amount and distribution of time required for executing control tasks. The used nested loop control architecture has an outer loop of MPPT generating th...

As a part of a hybrid microgrid, bidirectional DC-AC converters or interlinking converters allow to use the power not consumed by DC loads by injecting it into the grid, or by extracting power from the grid to supply the consumption of local DC or AC loads. This paper presents the study of a full-bridge single-phase grid-connected bidirectional inv...

This paper presents a proposal to charge and discharge valve-regulated lead-acid (VRLA) battery arrays integrated into microgrids by using the bidirectional Cûk converter with a multi-mode multi-loop control scheme based on sliding-mode control. The proposed control integrates the constant current - constant voltage - constant voltage charge method...

This paper proposes a control method to provide the function of Solar Panel Emulation (SPE) to a low-cost programmable DC source. The proposed control operates with base on the error between measurement of the conductance connected at the output of the SPE and the conductance obtained evaluating the I-V characteristic of the panel model. The princi...

This paper presents a control law based on Hybrid Dynamical Systems (HDS) theory for electronic inverters. This kind of systems are very suited for the use of such theory since they combine both kind of signals: continuous (voltages and currents) and discrete (on-off state of switches). Unlike previous applications of HDS to power converters, the s...

Context: Microinverters are widely used in modular photovoltaic installations but its operation with reduced power is limited to inject real power into the grid. One way to optimize the use of microinverters consist of providing them the Active Power Filtering (APF) capability, which allows its use as both distributed generation and compensation un...

This paper presents a comprehensive study of the digital implementation of the control requirements of the output stage of a two-stage solar microinverter. This approach uses a synchronized nested-loop controller which ensures the tracking of an internally generated high-quality current reference, the estimation and cancelation of the effect of the...

This paper describes the design and implementation of a Supervisory, Control & Data Acquisition (SCADA) system dedicated to realize on-line visualization and long-term monitoring of the performance of a single-phase single-module photovoltaic grid-connected installation. The main objective of this development is to ensure continuous monitoring of t...

This paper introduces a new hold-up time extension circuit (HTEC) with potential use in aircraft applications. The circuit is composed of a bidirectional version of the conventional buck-boost converter operating in Boundary Conduction Mode (BCM) and the corresponding control. The converter is used to charge and discharge an auxiliary capacitor use...

The conduction modes of the quadratic boost converter are explored in the context of high-dc-gain applications. A complete analytical description of the steady-state behavior of the converter operating in four possible inductor current discontinuous-conduction modes is presented. Boundaries between modes are determined together with the correspondi...

Email Print Request Permissions This paper develops a global model of a two-stage grid-connected microinverter which uses sliding-mode control laws in both stages. In the study, it is considered that the microinverter is fed by a current source representing the photovoltaic module with a capacitor connected in parallel. The model of the DC-DC stage...

This paper presents a proposal to control the output stage of a two-stage solar microinverter to inject real power into the grid. The input stage of the microinverter is used to extract the maximum available power of a photovoltaic module enforcing a power source behavior in the DC-link to feed the output stage. The work here reported is devoted to...

One of the more relevant aspects to improve the two-stage microinverter architecture consists on reduce the size of the required decoupling capacitor in order to enable the use of technologies with a greater service life such as thin-film capacitors. However, the diminution of the capacitor size introduces a deterioration of the power quality level...

This paper presents a simple method to generate low distorted sinusoidal references improving the power quality or the accuracy of power measurement in gridsynchronized applications. The proposed control strategy uses a half cycle detector, combining a square-wave discrete PLL with some functions embedded in a low-cost digital device. Using the pro...

A robust controller design to obtain output voltage regulation in a quadratic boost converter with high dc gain is discussed in this paper. The proposed controller has an inner loop based on sliding-mode control whose sliding surface is defined for the input inductor current. The current reference value of the sliding surface is modified by a propo...

These last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the ass...

Este artículo presenta un esquema de control completo para un micro-inversor fotovoltaico de dos etapas conectado a la red eléctrica, el cual utiliza modos deslizantes en diferentes variables para cubrir los diferentes objetivos de control. La topología propuesta incluye lazos independientes de control de potencia para los convertidores DC-DC y DC-...

Currently, interactivity is playing a fundamental role in engineering education because of the development of communications and systems. An important challenge is the effective use of computer tools that allow associating teaching methods with the new ways students learn. In the area of power electronics, recognizing different concepts of switchin...

The recent development of dual-stage photovoltaic micro-inverters motivates the study of DC-DC converter topologies with high-gain capabilities. Following this idea, a comparison of both static and dynamic performances of the known quadratic boost converter topologies is tackled in this paper. To achieve an accurate comparison, we use the same elec...

Este artículo presenta un método para obtener equilibrio de potencia en las etapas de un inversor multinivel monofásico asimétrico en cascada. El método se basa en la redundancia de estados, la cual considera la existencia de más de una combinación para conseguir un mismo nivel de la señal de tensión de salida del inversor. El procedimiento para ob...

La regulación de la tensión de salida en un convertidor elevador cuadrático es planteada en este artículo a partir de la aplicación del control en modo deslizante sobre la corriente de entrada y la modificación de la referencia de corriente a partir de un lazo externo de regulación proporcional-integral (PI). Se presenta un análisis del convertidor...

The digital implementation of a sliding-mode based control for a dual-boost rectifier with power factor correction (PFC) is presented in this paper. The proposed scheme has a current controller tracking a pure sine-wave reference, whose amplitude is a function of the output voltage error affected by proportional and integral terms. Thus, both power...

En este artículo se discute la importancia de diversificar las estrategias pedagógicas utilizadas en el laboratorio, con el fin de conseguir un rol más activo de la experimentación en la enseñanza de la electrónica de potencia. Las actividades propuestas están basadas en la necesidad de aplicar metodologías de enseñanza en el ambiente experimental,...

A transformer-less topology of a grid-connected photovoltaic micro-inverter applying sliding-mode control is discussed in this paper. The proposed structure is a dual-stage topology with a quadratic boost converter in the DC-DC stage and a full-bridge inverter in the DC-AC stage. The quadratic boost uses a multi-loop scheme with a sliding-mode curr...

A quadratic boost converter with high DC gain to step up the voltage of a standard photovoltaic panel up to 400 V is analysed. First of all, a comparative analysis among boost, quadratic boost and cubic boost reveals that the quadratic boost exhibits the best trade-off between duty ratio range and converter efficiency. A hysteretic comparator is em...

This paper presents the analysis of the quadratic boost converter operating in sliding-mode control in order to obtain high DC-gain. This approach uses a indirect control of the output voltage based on the use of a sliding surface defined with the input inductor current. The control law is argued through a stability test. The proposed control was i...

A digital implementation of a boost rectifier with power factor correction (PFC) is presented. The proposed control involves a current control loop and a voltage control loop. The current control loop is implemented with two different methods: (a) linear compensation; and (b) ON-OFF control. The voltage control loop is implemented with a proportion...

En este artículo se presenta una metodología de integración de actividades de enseñanza e investigación en electrónica de potencia basada en la aplicación de una nueva herramienta didáctica especializada en convertidores de potencia para fuentes conmutadas. Para lograr esta integración se definió como primer elemento una estructura computacional de...

Nowadays, thanks to the development of communications and systems, the interactivity has taken a fundamental role in engineering education. An important challenge is the effective use of computer tools that allow associating the teaching methods with the new way the students learn. In power electronics area, recognizing different concepts of switch...