Showing papers by "Matias Diaz published in 2022"

Digital twin based identification of degradation parameters of DC-DC converters using an Arithmetic Optimization Algorithm

Abstract: Power electronic converters are extensively used in various fields. The reliability and stability of converters are a significant concern in practice. So, the estimation of unknown parameters of power converters without additional hardware is necessary. The digital twin is a virtual dynamical model of a physical system. In this paper, identifying unknown circuit parameters of a buck converter is proposed using digital twin with Arithmetic Optimization Algorithm (AOA). First, the state variables of buck converter such as inductor current and output voltage are derived under steady-state and transient conditions for estimating the physical entity. Then, AOA is applied to estimate the unknown parameter of the buck converter based on the data coming from the digital twin model and its counterpart. Finally, the performance of AOA is compared with particle swarm optimization (PSO), and it concludes that AOA has fast convergence and efficient global search than PSO.

A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system

Abstract: It is commonly accepted that exoplanets with orbital periods shorter than 1 day, also known as ultra-short period (USP) planets, formed further out within their natal protoplanetary disk, before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here, we present the discovery of a four planet system orbiting the bright (V=10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of $\sim$ 13 hours, a mass of 1.42 $\pm$ 0.18 M$_{\oplus}$, a radius of $1.166^{0.061}_{-0.058}$ R$_{\oplus}$, and a mean density of 4.89$^{+1.03}_{-0.88}$ gcm$^{-3}$. Via Doppler spectroscopy, we discovered that the system hosts three outer planets on nearly circular orbits with periods of 6.6, 26.2, and 61.3d and minimum masses of 5.03 $\pm$ 0.41 M$_{\oplus}$, 33.12 $\pm$ 0.88 M$_{\oplus}$ and 15.05$^{+1.12}_{-1.11}$ M$_{\oplus}$, respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits, then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyrs, starting from an initial orbit of 0.02au. TOI-500 is the first four planet system known to host a USP Earth analog whose current architecture can be explained via a non-violent migration scenario.

Continuous Set Model Predictive Control for Energy Management of Modular Multilevel Matrix Converters

Abstract: The modular multilevel matrix converter (M3C) is an ac to ac power converter composed of 9 arms and is proposed for high power applications such as motor drive and wind energy conversion systems. Energy Control of the M3C is achieved using four circulating currents, and is frequently divided into the different frequency mode (DFM) and equal frequency mode (EFM). EFM is more challenging, because of the larger capacitor voltage oscillations that can be produced. The control schemes are typically different for EFM/DFM operation and this further increases the complexity. In this article, a continuous-control-set model predictive control for energy management of the M3C is proposed. The control scheme is based on solving an equality constrained quadratic programming problem, where the optimal solution is analytically obtained. The result is a single and simple control law to obtain the circulating current references, where good performance is achieved for both EFM and DFM. The proposed strategy is experimentally validated using a scaled-down M3C prototype composed of 27 power cells.

A Review of Generators and Power Converters for Multi-MW Wind Energy Conversion Systems

Abstract: The rated power of wind turbines has consistently enlarged as large installations can reduce energy production costs. Multi-megawatt wind turbines are frequently used in offshore and onshore facilities, and today is possible to find wind turbines rated over 15 MW. New developments in generators and power converters for multi-MW wind turbines are needed, as the trend toward upscaling the dimensions of wind turbines is expected to continue. Therefore, this paper provides a detailed review of commercially available and recently proposed multi-MW wind turbine generators and power converters. Furthermore, comparative analyses indicate the advantages and disadvantages of commercially available and promising technologies for generators and power converters at the multi-MW target.

Application of a Single-Phase Matrix Converter for Electric Vehicle Charging

Abstract: The Single-Phase Matrix Converter has been identified as a potential alternative to enable bidirectional residential electric vehicle charge due to its direct AC-AC conversion, high power density, and bidirectional power flow. However, implementation issues for single-phase circuits, such as providing a path for inductive currents and the development of modulation techniques for isolated operation, should be addressed. Consequently, this paper describes the design and modulation voltage of a Single-Phase Matrix Converter for electric vehicle charger applications. A modulation strategy is proposed based on four step commutation. Simulation results obtained using an RTBox real-time simulator are presented to validate the effectiveness of the Single-Phase Matrix Converter for electric vehicle charging.

Closed-Loop Adaptive High-Starting Torque Scalar Control Scheme for Induction Motor Variable Speed Drives

Abstract: This article proposes a closed-loop (CL) high-starting torque (HST) scalar control scheme (SCS) for induction motors (IM). It endows the recently proposed HST-SCS with high-output torque capability beyond starting after using an outer speed control loop feeding an inner current control loop with adaptive controllers. Presenting a cascade normalized adaptive passivity-based controller (N-APBC) for nonlinear systems encompassing the IM allows obtaining this result. It extends the normalized adaptive controller for the cascade case. As a result, it keeps the HST-SCS simple control scheme without needing variable observers or parameter estimators and employing tuning information only from the motor nameplate and datasheet. Test bench experiments with a 10 HP motor validate the proposal’s effectiveness. Comparative experimental results show that the CL HST-SCS has a required stator phase voltage lower than HST-SCS. The CL HST-SCS applies the adaptive starting voltage curve for a more extended time than HST-SCS, from the start to 1.9 s versus 1.2 s, respectively. Hence, CL HST-SCS assures HST not only for starting but almost up to 600 rpm, resulting in a smoother transient behavior than HST-SCS under this speed.

Experimental Assessment of a Modular Multilevel Converter using OPAL-RT Control and Power Stages

Abstract: Modular Multilevel Converters are being widely used in high-power applications such as High-Voltage Direct Current transmission due to the main advantages of scalability, modular configuration and high-quality power. For industrial applications, hundreds of power cells have to be connected in a cascade to reach high-power ratios. However, most of the current academic research is validated using prototypes equipped with a low number of power cells. Consequently, this paper presents the testing and start-up procedure of 60 power cells Modular Multilevel Converter test-bench based on an OPAL-RT real-time controller and power stage. Partial experimental results are presented.

Machine learning based condition monitoring of a DC-link capacitor in a Back-to-Back converter

Abstract: The utilization of power electronic converters has increased, and the significance of continuous operation is essential in various applications. Therefore, proper condition monitoring (CM) is vital for power converters to eradicate unpredictable maintenance. However, the existing CM techniques may require additional sensors or injection of controlled voltage to the converters. The following machine learning algorithms, such as a K-nearest neighbors (KNN), Support Vector Machine (SVM), and Naive Bayes (NB), have been proposed to monitor the condition of the dc-link capacitor in a Back-to-Back (BTB) converter. The dc-link voltage is measured, and a wavelet decomposition is employed for the feature extraction. Moreover, the performance index evaluates the efficacy of the different classifiers. Further, different datasets have been considered for the evaluation of the classifiers. From this analysis, it is found that the SVM classifier performs better than others.

Fast Terminal Integral Synergetic Control for Variable Speed Wind Turbine

Abstract: This work focuses on designing a nonlinear controller for maximum wind energy extraction with minimum stress on the drive train for variable speed wind turbines. A two-mass model is utilized for modeling the wind turbine. It can deal with aerodynamic nonlinearities and structural flexibility. Initially, conventional sliding mode controllers are adapted. However, these controllers have high oscillations on the drive train and control input. Further, to overcome the above issues, a fast terminal synergetic control, fast integral synergetic control, and fast terminal integral synergetic control with a wind estimator are proposed. Initially, a mathematical model was employed to test the controllers, and then a Fatigue, aerodynamics, structures, and turbulence 600 kW model was used to validate the existing and proposed control schemes. A comparative analysis has been conducted, and the results conclude that the fast terminal integral synergetic control improves the power capture with transient load reduction.

An Overview of Four-Leg Converters: Topologies, Modulations, Control and Applications

Abstract: In three-phase unbalanced systems, where the circulation of zero sequence current is necessary, four-leg converters provide a neutral connection for single-phase or other unbalanced loads typically utilized in three-phase distribution systems. In addition, control of the magnitude and phase of the zero-sequence voltage and/or current are also achieved using four-leg power converters. However, even when four-leg converters have become very important in several fields as for instance, four-leg microgrids and aerospace applications, a comprehensive review of the converter topologies, control methods, modulation methods and output filters have not been hitherto published. In this paper, a comprehensive overview of the state-of-the-art of four-leg converters is presented, based on the selection of over 400 papers published in journals and conferences, identifying mature and incipient topologies, modulation strategies, control schemes and applications. Each topic presented in this work is thoroughly discussed and reviewed, analyzing characteristics, implementation issues, and reported advantages and disadvantages to provide a comprehensive overview of the current research and future challenges in four-leg converters. The most important applications of four-leg converters are also discussed in this work, including stand-alone power supply, uninterruptible power supplies, grid-connected 4-leg inverters, ground power units for aerospace applications, active filtering for power quality enhancement, cooperative control of 4-leg converters for micro-grid applications, among others. Finally, future work and conclusions are highlighted in this paper.

Spinning up a Daze: TESS Uncovers a Hot Jupiter Orbiting the Rapid Rotator TOI-778

Abstract: NASA’s Transiting Exoplanet Survey Satellite (TESS) mission has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating ( vsin(i)=35.1±1.0 km s−1) early F3V-dwarf, HD 115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from Minerva-Australis, TRES, CORALIE, and CHIRON to confirm and characterize TOI-778 b. A joint analysis of the light curves and the radial velocity measurements yields a mass, a radius, and an orbital period for TOI-778 b of 2.76−0.23+0.24 M J, 1.370 ± 0.043 R J, and ∼4.63 days, respectively. The planet orbits a bright (V = 9.1 mag) F3-dwarf with M = 1.40 ± 0.05 M ⊙, R = 1.70 ± 0.05 R ⊙, and logg=4.05±0.17 . We observed a spectroscopic transit of TOI-778 b, which allowed us to derive a sky-projected spin–orbit angle of 18° ± 11°, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller-aperture telescopes such as Minerva-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars.

Control of an Ultrafast Electric Vehicle Charger based on a Series-Parallel Modular Multilevel Converter

Abstract: There is an ongoing trend of upscaling the nominal power of electric vehicle chargers to reduce the charging time of modern electric vehicles. As a result, ultra-fast electric vehicle chargers have reached megawatt power ratios for large EVs such as trucks and heavyweight vehicles. Therefore, Modular Multilevel Converters are acquiring popularity in EV charging applications. In this context, this paper proposes a novel EV charger based on a Series-Parallel Modular Multilevel Converter. In this proposal, the proposed converter is regulated to perform medium-voltage low-frequency alternating current conversion to low-voltage medium-frequency alternating current required for ultra-fast charging of electric vehicles. In addition, simulation results obtained with a 500 kW SeriesParallel Modular Multilevel Converter model using PLECS are presented to validate the proposed control and topology performance.

Control of a Shunt-Series Modular Multilevel Converter for Low-Frequency AC Transmission Systems

Abstract: Low-frequency AC transmission systems have been suggested as a suitable option for high-power transmission as they offer advantages compared to conventional high-voltage AC or high-voltage DC transmission systems. However, this application requires direct AC-AC conversion at high power-voltage ratios. In the context of high-power converters, several publications have been made on the Modular Multilevel Cascaded Converters, characterised as topologies with high voltage levels, full scalability, increased flexibility of control, and both high power and energy quality. Therefore, this paper studies a new topology for a Low-Frequency AC transmission system referred to as Shunt-Series Modular Multilevel Converter, a decoupled control strategy is proposed and simulation results are presented and analysed.

An Overview of Digital Twins Methods Applied to Lithium-Ion Batteries

Abstract: The continuous monitoring of the energy storage system in electric vehicles is essential for safe operation. In particular, most electric vehicles use Lithium-ion batteries due to their power and energy density, which can introduce instability in their performance. Recently, the use of digital twins has been able to provide more information to the battery management system for real-time decision-making. This paper presents an overview of the main methods for modeling lithium-ion batteries and the identification of parameters of these models, summarizing their advantages and disadvantages. In addition, the application of the linear parameter-varying representation and their contributions are discussed. Finally, digital twin methods applied to battery management systems are described, and their main functionalities are analysed.

Design and Implementation of an off-the-shelf Controller for Power Electronics Research and Teaching

Abstract: Several off-the-shelf real-time control systems are available for industrial and academic applications. These systems enable real-time control and prototyping of power electronic applications. However, most of these systems have a considerable cost and are inflexible, limiting their teaching and academic research usage. Consequently, this paper presents the design and implementation of a control platform based on a low-cost easy-to-program microcontroller from Texas Instruments. The proposed control platform is intended for rapid-control-prototyping, and it considers optic PWM outputs, isolated sensing of voltage/currents, multipurpose input-outputs, and hardware protections. Experimental results are presented to validate the usefulness of the proposed control platform.

Experimental Assessment of a Modular Multilevel Converter using OPAL-RT Control and Power Stages for Low-Frequency AC transmission systems

Abstract: Modular Multilevel Converters have been proposed for high-voltage direct current and Low-Frequency Alternating Current transmission systems according to benefits associated with their topologies, such as scalability, modularity, high voltage and power capacity. In industrial applications, hundreds of power cells have to be connected in a cascade to reach high-power ratios. However, most of the academic prototypes are equipped with a low number of power cells to validate academic research. Moreover, they are limited to conventional frequency operation in AC ports over the range of 50-60Hz. Hence, this paper presents the experimental results of a Modular Multilevel Converter test-bench comprised of sixty power cells and through OPAL-RT cabinets. Partial results validate a power flow regulation with power factor correction for low-frequency operation at 10-20 HZ.

Control of an Isolated AC-DC Matrix Converter for Vehicle-to-Grid Applications

Abstract: Fast electric vehicle chargers are commonly equipped with medium frequency transformers to provide galvanic isolation between the battery and the grid. Conventionally, several Alternating Current (AC) to Direct Current (DC) conversions are needed to insert the medium frequency transformer in the AC-DC grid-battery rectification process. Therefore, this paper presents an electric vehicle charger based on an isolated AC-DC Matrix Converter. A Space Vector Modulation technique is combined with Phase-Shifted Modulation to regulate the power transference at the same time as the proposed charger provides Vehicle-to-Grid services. Simulation results are presented to validate the effectiveness of the proposed topology and control strategy.

Review of Modular Multilevel Converters Applied to High Voltage AC and DC Transmission Systems

Abstract: Low-Frequency Alternating Current (LFAC) transmission systems have been recently proposed as an alternative to High Voltage Direct Current (HVDC) technology, mainly for offshore wind farms integration. Due to the high-power level required, Modular Multilevel Cascade Converters can be an appropriate alternative in these applications. However, most of the current research in MMCCs is focused on HVDC applications. Therefore, this paper reviews Hig Voltage Alternating Current, HVDC and LFAC transmission systems, comparing the potential application of the most studied AC-AC MMCC topologies in terms of component counts and appropriateness for LFAC transmission.

Control of a Modular Multilevel Converter for Fast Electric Vehicle Charging Applications

Abstract: Modular Multilevel Converters are considered one of the most suitable technologies for High-Voltage Direct Current transmission. However, they have been recently proposed in additional applications such as electric vehicle charging, Solid-State Transformers, and motor drives. In this context, this paper presents the modeling and control of a Modular Multilevel Converter for isolated power transference applications. In this proposal, the converter is regulated to perform Medium-Voltage Low-Frequency Alternating Current conversion to Low-Voltage Medium-Frequency Alternating Current required for fast charging of Electric Vehicles. In addition, simulation results obtained with a 500 kW Modular Multilevel Converter Serie model using PLECS are presented to validate the proposed control and topology performance.