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Publications (299)
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...
Two-stage cascaded DC–DC converters appear in many power electronics engineering applications. In this cascaded scheme, the first stage is called the source or upstream converter while the second one is called the load or downstream converter. If the downstream converter is controlled to maintain a tightly regulated output voltage on the load, it b...
This paper presents the detailed design of an active damping system for the stabilization of an open-loop boost converter in constant-power load (CPL) operation. The reported work analyzes the steady-state regime of the interconnection of a boost converter supplying a CPL, and a loss-free resistor (LFR) in series with the converter input port (SLFR...
A constant power (CP)-constant voltage (CV) protocol for battery charging is implemented in a conventional boost converter with output filter (BOF) by imposing loss-free resistor (LFR) behavior during the CP phase. To compare on equal basis the performance of the new CP-CV technique with the classical constant current (CC)–CV protocol, the latter i...
In this paper, the quadratic buck converter (QBC) is proposed as competitive alternative to implement a battery charger. Since QBC is a high order system, the required control is designed to follow the conventional constant-current constant-voltage protocol by means of three loops. Namely, i) an inner-loop operating in sliding mode to control the c...
This report presents the analysis, study, and simulation of an ultrafast charging station (UFCS) for electric vehicles (EVs) operating in steady state. The electrical architecture of the charging station uses an ac bus plus two dc buses and it is supported by a storage system based on batteries and super-capacitors. The power demand of the EVs is e...
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...
The use of Active Power Filters (APFs) in future power grids with high penetration of nonlinear loads is unavoidable. Voltage Source Inverters (VSIs) interfacing Photovoltaic (PV) generator could play the APF role in addition to power supply. In this paper, the control of a PV-fed multifunctional grid-connected three-phase VSI is addressed with non...
This paper presents a study of the existence conditions of limit cycles and mechanisms when losing their stability in an open-loop DC–DC boost converter loaded with a constant power load and operating in discontinuous conduction mode. First, the existence conditions are determined. Then, boundaries associated with different kinds of instabilities s...
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...
Constant power loading is an effect that appears in multiple-stage energy conversion systems with individually regulated switching power converters. In a two-stage system, an upstream or source converter drives one or more downstream or load converters. The downstream converters in a two-stage power conversion system are designed to provide the fas...
We propose a hybrid feedback law inducing self-oscillating behavior in second-order resonant converters. With our controller, the converter switches at the resonant frequency of its tank, without the need of external oscillators. In addition, the output amplitude can be adjusted by a reference signal ranging from zero to
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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...
The unstable on and off state trajectories of a boost converter supplying a constant power load (CPL) are appropriately combined using sliding-mode control (SMC) with a suitable surface to yield a stable trajectory that reaches a specified equilibrium point. Selecting the optimum surface involves a comparative analysis among potential candidates in...
The emergence of DC fast chargers for electric vehicle batteries (EVBs) has prompted the design of ad-hoc microgrids (MGs), in which the use of a solid-state transformer (SST) instead of a low-frequency service transformer can increase the efficiency and reduce the volume and weight of the MG electrical architecture. Mimicking a conventional gasoli...
Active Power Filter (APF) is a promising solution
to eradicate harmonics pollution in future power grids with
high penetration of nonlinear loads, including power electronic
converters, diode-rectifiers, arc furnaces, and electrified railways.
A cascaded H-Bridge (CHB) inverter could be a desirable
APF in medium and high voltage systems thanks to i...
This paper analyzes for the first time a two-loop sliding-mode control (SMC) of a high-order converter supplying a constant power load (CPL). The converter is a single-switch quadratic buck structure (QBC) interfacing a domestic 380 V DC bus to a CPL requiring a regulated voltage of 48 V DC. The converter is unstable in the absence of control and e...
Load and supply parameters may be uncertain in microgrids (MGs) due for instance to the intermittent nature of renewable energy sources among others. Guaranteeing reliable and stable MGs despite parameter uncertainties is crucial for their correct operation. Their stability and dynamical features are directly related to the controllers’ parameters...
We describe parallel and series resonant converters (PRC and SRC) via a unified set of input-dependent coordinates whose dynamics are intrinsically hybrid. We then propose hybrid feedback showing a self-oscillating behavior whose amplitude and frequency can be adjusted by a reference input ranging from zero to $\pi$ . For any reference value in tha...
Due to increasingly use of nonlinear loads in power grids, an Active Power Filter (APF) is unavoidable for guaranteeing the stable and efficient operation of power systems. APFs based on Cascaded Half-Bridge (CHB) inverters with low switching frequency can compensate high-order harmonics in medium and high voltage systems. Since grid-connected Phot...
The topology and management of a sustainable dual-bus, AC and DC, microgrid designed to operate connected to a weak grid is presented. AC+DC hybrid microgrids are a robust and cost-competitive solution for poorly connected areas, as can be found in rural or island electrification. The versatile microgrid proposed in this work is developed around a...
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...
Este artículo propone la arquitectura eléctrica de una estación de carga ultrarrápida de baterías que consiste en un sistema de distribución de energía híbrido con un bus de corriente alterna y dos buses de corriente continua de tensiones diferentes. La propuesta surge de la estimación de la demanda de potencia de los vehículos eléctricos (VE) que...
Damping is necessary for grid-connected converters with LCL filters to avoid their destabilizing resonant behavior. This paper presents three different damping methods for a grid-connected inverter with an LCL filter. The first one is a Passive Damping (PD) method in which a parallel resistor is added to the LCL filter capacitor. The second one con...
A unified set of input-dependent coordinates is proposed for the description of parallel and series resonant converters. The description naturally leads to a hybrid feedback control strategy for self-oscillating behavior. We show through a hybrid representation that the ensuing dynamics admits a unique almost globally attractive hybrid limit cycle....
This paper presents a systematic approach to synthetize constant power loads using switching converters under sliding-mode control. The generation of sliding motions is analyzed in converters with a series inductor in the input port and a switching function representing the error between the input power and a suitable power reference. The analysis...
This paper presents a nonlinear control based on pulse width modulation (PWM) and an estimation mechanism of the output power to regulate the output voltage of a boost converter supplying a constant power load (CPL). The controller uses three parameters Kp, KE and KA lending the regulator an adaptive nature. The behavior of the latter can be expres...
A general approach for the analysis and design of self-oscillating resonant converters is presented in this paper, for a particular class of circuits in which the change of input voltage polarity is caused by the zero-crossings of the input inductor current. The key features of the method are an analytical description in the time-domain of a spiral...
This book is the printed version of the 2019 special issue of Energies devoted to sliding-mode control of power converters in Renewable Energy Systems i. 16 selected papers reflect the state of the art in that field.
Photovoltaic (PV) ageing is known to cause a linear degradation of the short-circuit and maximum power point currents, which results in the corresponding power loss. Nonetheless, besides of degradation, also a dispersion of these currents has been reported in the past. Such a dispersion induces significant mismatches in the PV system, even in the a...
The first paper on dc-to-dc switching converters published in a scientific journal had only one page and didn't mention the term power converter in the description of that emergent family of circuits (1). Almost fifty years later, around 7000 patents have been issued on dc-dc conversion only in USA, what brings us to consider whether the interdisci...
This paper proposes a modular photovoltaic (PV) dc-Nanogrid (dc-NG) architecture for residential applications. The proposed architecture is based on the Loss-Free Resistor (LFR) concept. The dc distribution bus is supplied by PV panels, ac utility and a storage battery. The storage battery is connected to the main dc bus through a dc-dc bidirection...
Solar photovoltaic (PV) energy sources are rapidly becoming more popular. The PV system output power relies on the applied current or voltage nonlinearity and there exist a unique point called the maximum power point (MPP). For effective energy extraction from the PV system, this paper presents a new controller design strategy to track the MPP of a...
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...
In this paper, the start-up response of a digitally controlled dc-dc boost converter with a constant power load is studied. A mathematical expression of the system response during start-up is derived using a nonlinear averaged model. The time-domain response of the system during start-up when the converter is operating under current limitation mode...
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 presents the calculation of the minimum DC-link capacitance in power factor correction single-phase systems employing hysteretic current-mode control for low total harmonic distortion (THD). The proposed design can be applied to the cascade connection of converters in which the source converter can be modelled as a loss-free resistor (LF...
In this paper the modeling of storage elements and a unified theory liberated of the I-V characteristics of a specific technology is developed. First the definition of an ideal storage element with limited energy capacity is presented, then the semi-ideal storage properties are discussed. The addition of power conservative two-port network denoted...
The main goal of this research is to describe analytically the cascade connection of converters under constant power supply conditions, and propose simple control solutions that can cope with the potential instability caused by the CPL. With this aim, the use of different strategies such as linear control, sliding-mode control (SMC), digital SMC (D...
Dear Colleagues, Sliding-mode control (SMC) is increasingly used in power electronics due to its accurate dynamic analysis, fast resulting response, and inherent robustness in front of parametric changes. Its applications in renewable energies range from the control of micro-inverters in solar systems to the regulation of bidirectional battery char...
A nonlinear control strategy is proposed for output voltage regulation in a boost converter that supplies a constant power load. State-feedback linearization is used to transform the nonlinear average dynamics of the inductor current in the converter into a linear average dynamics of the inductor current in a virtual mesh, which consists in the ser...
This paper presents the analysis and design of a min-type strategy to control a synchronous boost converter in continuous conduction mode. The strategy uses a nonlinear switching surface to establish the change of topology in the converter and is analyzed by means of a sliding-mode control approach. Subsequently, the min-type strategy is modified b...
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...
The cascade connection of two dc-dc switching converters for constant power supply is studied. The source converter is of boost type while the load converter is of buck type. The natural unstable behaviour of the cascade connection for both ON and OFF states of the boost converter is counteracted by a sliding-mode control strategy that combines uns...
This paper proposes a bidirectional dc-dc converter (BDC) based on Sliding Loss Free Resistor (SLFR) used for microgrid applications. The dc distribution bus of the microgrid is provided by PV panels and ac utility to feed the downstream loads and the BDC which essentially operates in the buck mode to charge the battery to a certain nominal value....
This paper deals with the global dynamical analysis of an H-bridge parallel resonant converter under a zero current switching control. Due to the discontinuity of the vector field in this system, sliding dynamics may take place. Here, the sliding set is found to be an escaping region. Different tools are combined for studying the stability of oscil...
Resonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this paper, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the a...
A variable bus voltage DC microgrid (MG) is simulated in Simulink for optimization purposes. It is initially controlled with a Voltage Event Control (VEC) algorithm supplemented with a State of Charge Event Control (SOCEC) algorithm. This control determines the power generated/consumed by each element of the MG based on bus voltage and battery Stat...
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...
Hysteretic comparators are often used to implement sliding-mode controllers or other type of discontinuous regulators for power switching converters. Their design is usually performed analogically yielding robust and fast controllers that can even allow converter operation with high values of duty cycle. A new analogue implementation based on a low...
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...