Examinando por Autor "García, Germain"
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- PublicaciónSólo datosA Single-Phase Transformer-Based Cascaded Asymmetric Multilevel Inverter With Balanced Power Distribution(IEEE Access, 2019-07-22) Lopez-Santos, Oswaldo; Jacanamejoy-Jamioy, Carlos A.; Salazar-D’Antonio, Diego F.; Corredor-Ramírez, Julian R.; García, Germain; Martinez-Salamero, LuisThis 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 switching patterns to synthesize an output signal of until 35 levels. As it is developed in the paper, optimum switching patterns for the proposed ratio allow reducing typical power unbalance produced by commonly used ratios in four stage multilevel inverters (1:2:4:8 and 1:3:9:27). The proposed method consists on determining off-line the best switching patterns for minimizing deviation error, and then, storing them as lock-up tables in the digital device controlling the inverter. By permanently reproducing the selected switching patterns, balanced power distribution is achieved. A closed-loop control approach to regulate the RMS value of the output voltage compatible with the proposed method is also developed. The experimental results using a laboratory prototype are presented validating the entire approach.
- PublicaciónSólo datosA Unified Approach for the Control of Power Electronics Converters. Part I—Stabilization and Regulation(Applied Sciences, 2021-01-11) García, Germain; López-Santos, OswaldoThis 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 appropriate context: linear, nonlinear, switching, and hybrid control, to cite the most important. In recent years, a considerable effort has been made to derive control design methods taking into account the specificities and properties of the complex behavior of these systems, going beyond the numerous techniques based on approximated models or focused on the specific converter topology under study and, in that way, making a step towards a desirable genericity level. It is the objective of this work to go a step further trying to tackle the control of power converters in a unified way. The idea is to avoid, as much as possible, the use of approximations and exploit all the mathematical properties of the associated switched models. Writing them in a specific way, it is possible to deal with a lot of problems of interest whose solutions are based on assumptions which are the expressions of some kind of practical feasibility, and then closely related to the existence of solutions to the studied problems. In some cases, the resulting controls have an inevitable complexity level which reflects one of the problems under study. For such situations, the implementation issues are important and are not discussed in details in this paper. The proposed methods are illustrated by numerical simulations conducted with the help of PSIM software. This research work is decomposed into two parts, the first one focused on stabilization problems is developed in this paper. The other one concerning the tracking problems will be developed in a future paper.
- PublicaciónSólo datosA Unified Multimode Control of a DC–DC Interlinking Converter Integrated into a Hybrid Microgrid(Electronics, 2019-11-08) López-Santos, Oswaldo; Aldana-Rodríguez, Yeison Alejandro; García, Germain; Martínez-Salamero, LuisDC–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 using the proposed control, the converter can transfer power between the buses when the other converters regulate them, or it can ensure the voltage regulation of one of the buses, this originating from its three operation modes. The proposed control scheme is very simple and provides a uniform system response despite the dependence of the converter dynamic on the operating point and the selected mode. Simulation and experimental results validated the theoretical development and demonstrated the usefulness of the proposed scheme
- PublicaciónSólo datosAdaptive Sampling Frequency Synchronized Reference Generator for Grid Connected Power Converters(Communications in Computer and Information Science, 2018-09-13) López-Santos, Oswaldo; Tilaguy-Lezama, Sebastián; García, GermainThis 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, high power factor rectification, and grid integration of renewable energy sources. A hybrid analog-digital implementation is proposed integrating an Adaptive Sampling Frequency Moving Average Filter (ASF-MAF) and a discrete-time Proportional-Integral (PI) controller into a Digital Signal Processor (DSP) operating with a sampling frequency defined by an external hardware-based Voltage Controlled Oscillator (VCO). The main advantages attributed to the method are immunity to harmonic content, accuracy in computations despite of frequency changes, flexibility to produce phase displacements and reduced computational cost. Performance of the proposal was verified by means of simulation and experimental results.
- PublicaciónSólo datosAnalysis, Design and Implementation of a Static Conductance-Based MPPT Method(IEEE, 2018-05-15) López-Santos, Oswaldo; García, Germain; Martinez-Salamero, Luis; Giral, Roberto; Vidal-Idiarte, Enric; Merchán-Riveros, María C.; Moreno-Guzman, YamelThis 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 increase the conductance at which the PV array is forced to operate until the MPP is reached. Simultaneously, the error is used to change the power reference until the trajectory of this reference in the P-G curve enters a limit cycle around the MPP. The P-G curve is derived from a piecewise linear approximation of the current versus voltage (I-V) curve, which facilitates the analytical description of the tracking operation. The technique reported can also be implemented by means of simple analog or digital circuitry and requires two sensors to measure the instantaneous PV array current and voltage. It uses only four tuning parameters, which are selected depending on the maximum value of the derivative of the power with respect to the conductance. The theoretical predictions are verified with simulations and experimental results. The latter show that the procedure performs well enough to be favorably compared with the most efficient MPPT methods.
- PublicaciónSólo datosComparison of quadratic boost topologies operating under sliding-mode control(2013 Brazilian Power Electronics Conference, 2013-10-31) Lopez-Santos, Oswaldo; Martínez-Salamero, Luis; García, Germain; Valderrama-Blavi, Hugo; Sierra-Polanco, TomásThe 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 electronic components and the same control scheme. Considering its advantages, a sliding-mode control law has been proposed to reach a stable equilibrium point in the switching converters. The sliding surface uses only the input current following a constant reference. This current reference is adjusted to obtain an output voltage of 400 V for an input voltage between 15 and 25 V and an output power between 20 and 120 W. The local stability of the proposed control law is tested by using the Routh-Hurwitz criteria. The comparison is accomplished using simulation results to disclose the best configuration in terms of efficiency, dynamic response and applicability in photovoltaic generation.
- PublicaciónSólo datosDouble Sliding-Surface Multiloop Control Reducing Semiconductor Voltage Stress on the Boost Inverter(Applied sciences, 2020-07-17) López-Santos, Oswaldo; García, GermainSliding-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 structure involving outer loops that generate references for one or two sliding surfaces defined using linear combinations of inductor currents and capacitor voltages. As expected, all proposed methods share the inherent robustness and insensitivity to the uncertainties of SMC, which are the reasons why one of the few comparison criteria between them is the simplicity of their implementation that is evaluated according to the required measurements and mathematical operations. Furthermore, the slight differences between the obtained dynamic performances do not allow a clear distinction of the best solution. This study presents a new SMC approach applied to a boost inverter in which two boost cells are independently commutated. Each of these boost cells integrates an outer loop, enforcing the tracking of harmonic-enriched waveforms to the capacitor voltage. Although this approach increases by two the number of measurements and requires multiloop controllers, it allows effective alleviation of the semiconductor voltage stress by reducing the required voltage gain. A complete analytical study using harmonic balance technique allows deducing a simplified model allowing to obtain a PI controller valid into to the whole set of operation conditions. The several simulation results completely verified the potential of the control proposal and the accuracy of the employed methods.
- PublicaciónSólo datosEfficiency Analysis of a Sliding-Mode Controlled Quadratic Boost Converter(IET Power Electronics, 2013-02-01) Lopez-Santos, Oswaldo; Martínez-Salamero, Luis; García, Germain; Valderrama-Blavi, Hugo; Mercuri, Daniel O.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 employed as a modulator to ensure the converter operation with high values of the duty ratio without risk of modulation saturation. A twoloop sliding-mode control is used to regulate the output voltage. An internal loop controls cycle by cycle the input current whose reference is established by an outer loop that processes the output voltage error by means of a proportional-integral compensating network. The measured results in a 100 W prototype operating in continuous conduction mode of average values, ripples, frequency and efficiency for different equilibrium points are in good agreement with the theoretical predictions.
- PublicaciónSólo datosEmulation of a Photovoltaic Module Using a Wiener-Type Nonlinear Impedance Controller for Tracking of the Operation Point(Applied Computer Sciences in Engineering, 2017-10-01) López-Santos, Oswaldo; Merchán-Riveros, María C.; Salas-Castaño, Maria C.; Londoño, William; García, GermainThis 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 principle of operation is that the output of the controller modifies the value of the voltage introduced into the W-Lambert function to obtain the corresponding current enforcing the regulation of the measured conductance. In this paper, a controller composed by a nonlinear static gain and a conventional PI controller is proposed. The controller architecture configures a Wiener system structure which ensures the stable convergence of the real SPE variables to the values defined by the model. Simulation results are presented evaluating the dynamic performance of the system for irradiance and load variations. SPE method is implemented using simple measurement and conditioning circuits interacting with an application developed in LabVIEW through a data acquisition card. This implementation provides a complete solution highly applicable in research and industrial development.
- PublicaciónSólo datosEvent-Triggered Digital Implementation of MPPT for Integration of PV Generators in DC Buses of Microgrids(Applied Computer Sciences in Engineering, 2018-09-13) López-Santos, Oswaldo; Merchán-Riveros, María C.; García, GermainThis 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 the conductance reference used by an inner loop which regulates the input conductance of a DC-DC converter. This last loop enforces a sliding-mode loss-free-resistor behavior for the power converter by means of a simple hysteresis comparator. Computations required by the MPPT algorithm are synchronously executed by the two possible commutation events produced by the inner loop during a switching period. Then, the acquisition of signals must be activated only at an instant before each one of the switching events, releasing the most of the time to implement other tasks. This last characteristic and the use of a nested loop control architecture facilitate the integration of the other essential control functions for photovoltaic (PV) generators in microgrids. Simulation and experimental results confirm the high potetialities of this implementation approach.
- PublicaciónSólo datosHybrid control scheme for a half-bridge inverter(IFAC-PapersOnLine, 2017-10-01) Albea Sanchez, Carolina; López-Santos, Oswaldo; Zambrano-Prada, David; Gordillo, Francisco; García, GermainThis 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 studied problem can be considered as a tracking problem since the objective is to generate a desired ac voltage from a dc source. The effectiveness of the resultant control law is validated by means of simulations and experiments.
- PublicaciónSólo datosOn the Practical Stability of Hybrid Control Algorithm With Minimum Dwell Time for a DC-AC Converter(IEEE Xplore, 2018-10-05) Albea Sanchez, Carolina; López-Santos, Oswaldo; Gordillo, Francisco; Zambrano-Prada, David; García, GermainThis 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 stability results are induced for this tracking problem, ensuring a minimum dwell time associated with an Linear–Quadratic Regulator (LQR) performance level during the transient response and an admissible chattering around the operating point. The effectiveness of the resultant control law is validated by means of experiments.
- PublicaciónSólo datosSliding Mode Control of the Isolated Bridgeless SEPIC High Power Factor Rectifier Interfacing an AC Source with a LVDC Distribution Bus(Energies, 2019-09-07) López-Santos, Oswaldo; Cabeza-Cabeza, Alejandro J.; García, Germain; Martinez-Salamero, LuisThis 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 source and a low voltage direct current (LVDC) distribution bus. The sliding-mode control is used to ensure the tracking of a high quality current reference at the input side, which is obtained from a sine waveform generator synchronized with the grid. The feasibility of the proposal is validated using simulation and experimental results, both of them confirming a reliable operation and showing good static and dynamic performances.
- PublicaciónSólo datosSliding-mode control of a transformer-less dual-stage grid-connected photovoltaic micro-inverter(10th International Multi-Conferences on Systems, Signals & Devices 2013 (SSD13), 2013-09-02) Lopez-Santos, Oswaldo; Martínez-Salamero, Luis; García, Germain; Valderrama-Blavi, HugoA 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 current controller and a proportional-integral (PI) compensator regulating the output voltage. The full-bridge inverter injects real power to the grid by means of a sinusoidal reference sliding-mode tracking-loop whose amplitude is defined by a maximum power point tracker (MPPT). This preliminary work involves an analytical discussion and several simulation results of each converter and of the overall system.
- PublicaciónSólo datosSliding-mode indirect control of the quadratic boost converter operating in continuous conduction mode or discontinuous conduction mode(2012 IEEE 4th Colombian Workshop on Circuits and Systems (CWCAS), 2013-01-11) Lopez-Santos, Oswaldo; García, Germain; Martínez-Salamero, Luis; Valderrama-Blavi, HugoThis 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 implemented in MATLAB simulations with a quadratic boost operating in continuous conduction mode (CCM), and another one in discontinuous conduction mode (DCM). The results validate the theoretical approach and illustrate the advantages and drawbacks of two operational modes.
- PublicaciónSólo datosSpecial Issue “Advances in Control of Power Electronic Converters”(Applied Sciences (Switzerland), 2021-05-18) Lopez-Santos, Oswaldo; García, GermainThe 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 DC loads from low DC voltage levels, whose proper operation is achieved by means of specialized control systems. Simultaneously, the power converters used for conventional industrial applications have evolved thanks to the application of new control methods, and the combination of these with well-established techniques. 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.