ROPEC 2018: XX IEEE INTERNATIONAL AUTUMN MEETING ON POWER, ELECTRONICS AND COMPUTING
PROGRAM FOR FRIDAY, NOVEMBER 16TH
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09:00-10:20 Session 9A: Power
Location: Artemisa
09:00
State-feedback linearization using a robust differentiator combined with SOSM super-twisting for controlling the induction motor velocity

ABSTRACT. In this paper the authors propose a robust controller by applying state-feedback linearization technique combined with the super-twisting algorithm as control law, which is applied to control the velocity of the squirrel-cage induction motor under unknown load conditions directly coupled to an induction generator, which delivers the generated energy toward the utility grid. The controlled output variables of the system are: the angular rotor velocity and the square modulus of rotor flux linkages. We estimate the time derivative of the tracking error variable through a robust differentiator to define the sliding surface for control purposes. Consequently, the load torque estimation via an observer is not necessary. By using a robust differentiator in the controller design, the resulting control law does not depend on the system parameters, which are usually difficult to obtain, which constitutes one of the main contributions of this paper. Finally, real time experiments are carried out in a laboratory prototype to validate the robust operation of the proposed velocity controller.

09:20
Implementation of synchronization stage (SVPWM) of a fuzzy controller for an AC Servomotor System

ABSTRACT. This article presents the implementation of a modulation strategy based on Space Vector Pulse Width Modulation (SVPWM), coupled to a fuzzy controller for AC servomotors. The controller and the modulation strategy were embedded in an 8-bit microcontroller. Speed tests were executed with a predefined load, to determine the performance of the system. An algorithm was developed to comply with the different commutation states for the appropriate switching of the windings.

09:40
A Study of a Three-Phase Four-Wire Shunt Active Power Filter for Harmonics Mitigation

ABSTRACT. The electrical power quality in three phase four wire systems, feeding nonlinear loads, can be improved by using active power filters (APF) in order to mitigate the total harmonic distortion. Harmonic currents and voltages produced by single phase, non-linear loads, which are connected phase to neutral in a three phase, four wire system, are third order, zero sequence harmonics. These third order, zero sequence harmonic currents, unlike positive and negative sequence harmonic currents, do not cancel but add up arithmetically at the neutral bus, and can be greater than the current of each of the phases. The danger that arises is an excessive overheating of the neutral, since there is no circuit breaker in this conductor, which limits the current, as occurs with the phase conductors. An excessive current in the neutral can also cause an excessive voltage difference between the neutral conductor and ground. This paper presents the theory and design of the control system used to mitigate harmonic problems in three-phase four-wire systems based on a split capacitor topology. Due to split capacitor topology has midpoint between the capacitors, this point can be used for the neutral return path, and thus, the entire neutral current flows through the DC bus capacitors reducing the number of switching devices. Simulation results are shown to validate the proposed procedures.

10:00
Modeling and Identification of Batteries Parameter Using an Equivalent Electric Circuit

ABSTRACT. We present a mathematical model that describes the electrical dynamics of a lithium-ion battery associated with its state of charge and its output voltage in open circuit. The proposed model describes this dynamics considering the resistorcapacitor configurations in parallel in the battery. This model is non-linear and it depends only on battery temperature and current. We use the least squares approach to estimate the model parameters considering fits by means of a sixth-order polynomial and an exponential function, which we applied to experimental data published in 2012 and 2016 for ion-lithium batteries. We show the battery voltage as a function of its charge state when we simulate the equivalent electrical circuit of the battery considering a specific profile on current demand. Finally, we show that the proposed model maintains the charging/discharging profileof the battery according to the current demand profile.

09:00-10:20 Session 9B: Electronics
Location: Diana (A)
09:00
On the Implementation of a 3D Space Vector Modulation Algorithm

ABSTRACT. This paper reports on the development of an efficient C-script implementation of a 3D Space Vector Modulation (3D-SVM) algorithm for a Four-Leg Voltage Source Inverter. The algorithm takes advantage of the finite-set of space-vectors in order to avoid calculating a matrix inversion. The algorithm is implemented in a C-script and tested by simulation in PLECS.

09:20
Footbridges Vibration Reduction based on Semiactive Control by using Magnetorheological Dampers and Optimal Control

ABSTRACT. A footbridge is a structure designed for pedestrians, cyclist or animals to allow to cross roads safely or to cross water or railways in areas where there are no nearby roads. Footbridges are constructed with materials such as concrete, steel and timber, and modern ones are designed as slender and light structures for them to be more aesthetic and economic, but may lack of enough stiffness and damping, that during service conditions might produce excessive vibrations overpassing comfort limits for human beings and may compromise structural integrity. This work presents the synthesis of a nonlinear optimal control strategy for reducing vibrations in footbridges by means of using magnethoreological dampers (MRD). A proposed discretized model, with eleven translational degrees of freedom (DOF) of a real footbridge is analyzed in simulation as a case study, whose dynamical response involves displacement, velocity and acceleration to initial conditions (free vibration). The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one MRD installed at the span center.

09:40
Finite time stabilizing bounded controls via orthogonal polynomials

ABSTRACT. Using orthogonal polynomials corresponding to a function distribution $\sigma(\tau,\theta)$ defined on $\tau\in[0,\infty)$ and parameter $\theta\geq0$, a family of bounded positional controls $u$ that stabilizes at finite time a family of Brunovsky systems of dimension $n$ is derived. The parameter $\theta=\theta(x)$ is Lyapunov type function which we use to construct the positional control $u=u(x,\theta(x))$.

10:00
Collision and Tension Analysis of Cable-Driven Parallel Robot for Positioning and Orientation

ABSTRACT. This electronic document is a “live” template and already defines the components of your paper [title, text, heads, etc.] in its style sheet. In recent years cable-driven parallel robots have been utilized in industry to perform automation tasks over large workspaces. In addition, this type of robots are characterized by large load handling capacities thus they have become a highly valued tool in industry. The present article shows the simulation results which determines the feasibility of positioning and orienting of a robot actuated by eight wires in a suspended structure in a determined point in space, analyzing the behavior of tension of the cables and the distance between elements that can collide. The process comprises the following steps: establishment of a target position and orientation for the final effector, generation of a rectilinear path that progresses through intervals until reaching the desired position and orientation, calculation of cable lengths for each interval, determination of collisions between cables, and between cables with end-effector segments by calculating their distances. Additionally, a cartesian trajectory was generated in order to compare different characteristics between trajectories, cable tensions and possible collisions. Finally, feasibility of cable tensions is evaluated, considering that cables bends without resistance on compressive efforts. The developed program allows to determine the evolution of the trajectory, possible crosses between cables, and the feasibility of the selected position and orientation for the end effector.

09:00-10:20 Session 9C: Renewable Energy
Location: Diana (B)
09:00
Online calculation of torque balance for power control of a DFIG connected to an electrical grid

ABSTRACT. A Newton-Raphson based algorithm is proposed for the solution of the transcendental equation that describes the torque balance between a Wind Energy Conversion System (WECS) and an Electrical grid. The WECS is considered operating in a different condition than the maximum power and with a passivity-based controller. The torque balance is calculated online to feed the control and regulate the active and reactive power dispatched to the grid for different wind speeds. The number of iterations is adjusted for a convergence criterion of 0.0001. The maximum time required by the proposed algorithm at each integration step on the passivity-based controller is 0.00366s. The numerical results were obtained using commercial software on a 8 GB RAM computer with 1.8 GHz. The accuracy of the algorithm is verified with results reported in literature.

09:20
Nonlinear Optimal Control for a Grid-Connected Photovoltaic System

ABSTRACT. This work presents the application of nonlinear optimal and robust control strategies, in combination with a maximum power point tracking algorithm (extremum seeking), for the control of a grid-connected photovoltaic system, through a LCL filter. It is important to mention that due to the intermittency in generation due to alternate sources, such as solar energy, the fact of the implementation of maximum power tracking algorithms is justified. The aforementioned control strategies are applied as a whole to a buck-boost converter and a three-phase inverter

09:40
Modeling and Performance Analysis of 1-MW PV Farm for Varying Solar Irradiance Conditions

ABSTRACT. Actually, an imperative need for installing new renewable energy sources in small and medium scale has been motivated in the world due to the high cost tendency of fossil fuels, emissions of polluting gases and growth in electricity demand. This article presents the preliminary study for the installation and start-up of a 1-MW photovoltaic project interconnected to a 13.8-kV distribution network, considering the design, modeling, simulation and components necessary for its installation. The modeling of photovoltaic cells, the operation of a DC/AC energy conversion system are discussed in detail. The developed model makes due account for the SPWM modulation, as well as the controls implemented for the maximum extraction of power from the photovoltaic array (MPPT), active and reactive power controls and DC voltage regulation, for varying solar radiation conditions.

10:00
Maximum wind energy capture in a wind system using a doubly-fed induction generator

ABSTRACT. On this paper the authors propose an analysis of a scalable wind system on dq frame using a doubly-fed induction generator. The wind system model includes the turbine and the doubly-fed induction generator model, where the turbine model contains a mathematical function to approximate the power coefficient, the power and torque produced by the wind turbine. Both models are presented in detailled form. The closed-loop wind system controller is described, where the controlled output variables are: the electromagnetic torque to maximize the wind energy capture and the stator reactive power of the energy delivered to the grid to control the power factor. Finally, simulation results are shown to validate the robust operation of the proposed wind system controller.

09:00-10:20 Session 9D: Computing
Location: Venus (A)
09:00
Radial Basis Function Neural Network for modelling an Electrical Discharge Machining drilling process

ABSTRACT. Experimental research for prediction of Material Removal Rate in an Electrical Discharge Machining drilling process is presented in this study. The process was performed in High Strength Steel which is extensively used in automotive industry for truck chassis manufacturing. The prediction model was computed by a Radial Basis Function Neural Network. With the aim to increase the prediction capability of the Neural Network, a Genetic Algorithm was used to tune its weights. An experimental series were carried out to get raw data and explore the influence of the machining parameters, namely: gap voltage, machining current and pulse frequency, as well as electrode configuration (single or multi-channel tubular). Experimental results reveal that the modified Neural Network, satisfactorily predicts the Material Removal Rate for each experimental condition.

09:20
An expert system to recommend contents and guided visits for children: a practical proposal for the Pumapungo Museum of Cuenca, Ecuador

ABSTRACT. In a globalized world like the one we live in nowadays, it is fundamental for every nation to preserve the cultural heritage. In this line, the UNESCO estimates that, if nothing is done, half of 6000 plus languages spoken today will disappear by the end of this century. For these reasons, in this paper, we present an expert system that has the aim of helping children during their visits to the museum. Our proposal relies on rule-based reasoning and focuses on helping which exhibits can be visited according to children's preference without leaving aside the possibility of introducing new contents (exhibition rooms) to trigger the visitors' preference on new cultural topics. The system was evaluated by a team of experts according to the following criteria: effectiveness, concordance, and novelty.

09:40
An ontological network to identify accessibility metadata in learning objects: an approach based on Web Content Accessibility Guidelines, schemas, and disabilities analysis

ABSTRACT. According to the guidelines provided in the UNESCO program Learning for All,'' the stakeholders (governments, institutions, teachers, instructional designers and quality assurance/qualification recognition bodies) are responsible on the development of contribution to guarantee the quality access learning for persons with disabilities or special needs. For this reason, in this paper, we present a proposal for an ontological network to model the knowledge of accessibility guidelines related to Learning Objects (LO). Our approach relies on the Web Content Accessibility Guidelines (WCAG 2.0), the Schema accessibility metadata, and a novel proposal to include the preference according to disability characteristics.

10:00
Digitized Documents Validation using Digital Signatures and QR Code

ABSTRACT. A digital document validation scheme is presented in this article. The scheme is applied to a higher education institution. To perform the validation, we used algorithms to generate SHA256 and RSA digital signatures and the QR algorithm. This article describes its functionality and implementation using the Java Programming Language.

09:00-10:20 Session 9E: Power Converters
Location: Afrodita (A)
09:00
Kinetic energy recovery system based on a grid-tied three-phase power inverter for metro trains

ABSTRACT. This paper addresses the design of a kinetic energy recovery system. The energy recovery system is aimed to recover the energy regenerated by metro trains during their braking stage. The system is based on a grid-tied three-phase power inverter. Active and reactive power are injected into the grid by the power inverter when the train is regenerating energy. Synchronization of the power inverter to the grid is based on an SRF-PLL reference-frame technique. An energy management algorithm based on rules that determine the conditions under which the power is injected into the electrical grid is proposed. Finally, the results are validated by simulation in real time using a Hardware In The Loop system (Typhoon HIL 402) that is focused on power electronic applications.

09:20
Estimate electrical potential of municipal wastewater through a micro-hydroelectric plant

ABSTRACT. Renewable energy is extracted from Ultra-Low- Head hydraulic resources through a set turbine-generator which converts the kinetic energy of the water to electrical one. However, this resource has not been attractive to exploit since the applied engineering to large-scale water resources is not the same to design Mini-Hydraulic Plants. Since the natural fluctuations of the resources do not permit a constant energy exchange, the system needs to be evaluated with different flow rates to be as efficient as possible. Thus, this paper focuses on the analytical design of a Permanent Magnet Synchronous Generator (PMSG) coupled to a Hydraulic Propeller Turbine which be able to generate electricity in a continuous way. The variable flow rate is given by a Municipal wastewater plant during a period of time. The methodology was divided in three steps: the first one estimates the available energy from the water resource though the Flow Duration Curve (FDC). The second one relates the design variables of the hydraulic turbine created by an virtual turbine-generator set to the water resource energy. The third step transforms the mechanical energy to electrical one though the dimensions of a PMSG. Finally, with this methodology could be created different magnet capabilities of the generator in order to exploit the majority of the available power of a variable hydraulic resource.

09:40
A transformerless boost-resonant DC-DC converter with high voltage ratio for MVDC applications

ABSTRACT. This paper presents a novel electronic transformerless boost-resonant DC-DC converter, which is intended for interconnected high or medium voltage DC grids. The proposed DC-DC converter is composed by two inductances, one capacitor and five switches which are responsible for the interaction of the boost and resonant converters, the resonant converter is composed by a resonant inductor and resonant capacitor, while the boost converter is composed by a boost inductor. This paper discusses a classification of DC-DC converters in topologies, the principles of operation of proposed converter, control, modular connection, simulation in order to probe the effectiveness of the converter and a case of study in a HVDC link, using the proposed converter as a sending node and a MMC converter as a reception node.

10:00
Analysis of Synchronverters and Droop Control Scheme During Microgrid Operation: A Performance Comparison Approach

ABSTRACT. A comparative analysis of synchronverter controller and droop control scheme for microgrids is presented in this paper. The aim of this analysis is to give insight of which controller can perform well in microgrids with certain operating requirements taking into account the technical and operational characteristics as well as advantages and disadvantages of both controllers. To support the analysis, two numerical simulations are carried out in order to evaluate the theoretical performance of both controllers under operating conditions commonly observed during microgrids operation. The obtained results are discussed later in order to delimit the application field of each controller and to establish some conclusions.

09:00-10:20 Session 9F: Condition Monitoring of Electric Machines and Systems
Location: Afrodita (B)
09:00
Efficiency monitoring of photovoltaic inverters considering weather conditions

ABSTRACT. The study in the Renewable Energies has gained attention in the last decades due to these kinds of energies could help to give solution to the actual energy consumption problem. Between the different renewable energies, the solar energy is of great interest since this energy is cheap, reliable, non-polluted and can be widely distributed. The use of this energy is exploited through the photovoltaic panels technology, which integrates a power converter among its elements in order to perform the signal conversion from the DC level to the AC level, since almost all the electric and electronic devices make use of the AC signal source. However, the energy conversion efficiency strongly depends of the efficiency of the power inverter and several factors affect in this process, for instance weather conditions. A system designed to monitor the signals of a photovoltaic panel would help to evaluate this efficiency. This paper shows how the weather conditions directly affect the efficiency reached by the photovoltaic power inverter and stablish the relationship between these conditions and the photovoltaic inverter efficiency through a proprietary system PQ-UAQ. Several tests were carried out storing the data of voltage, current, irradiance and temperature for three days with different climatic conditions and then the data was processed to determine the relationship existing between them. The obtained results demonstrate that weather conditions affect in the irradiance and temperature profiles affecting in turn the photovoltaic inverter efficiency due to the existing correlation between them.

09:20
Time-Domain Diagnosing Algorithm for Automatic Broken Rotor Bar Detection in Induction Motors

ABSTRACT. Induction motors are one of the most utilized electrical machines in the industry. Therefore, to guarantee their correct operation is of vital importance. During their operation life the motor tends to fail, and one of the most studied faults in the literature is the broken rotor bar condition since it can occur without apparently affecting the motor operation. Then, opportune fault detection is desired. Many researches attempt to solve the problem. However, methodologies that efficiently determine the motor condition in an automatic way are still required. The contribution of this work is to propose a low-complex algorithm to detect and to classify automatically the BRB fault, even in its incipient stage. The obtained results demonstrate that the proposed algorithm can efficiently distinguish between Healthy, Incipient, 1 BRB and 2 BRB conditions

09:40
Condition Monitoring Strategy Based on Spectral Energy Estimation and Linear Discriminant Analysis Applied to Electric Machines

ABSTRACT. Condition-based maintenance plays an important role to ensure the working condition and to increase the availability of the machinery. The feature calculation and feature extraction are critical signal processing that allow to obtain a high-performance characterization of the available physical magnitudes related to specific working conditions of machines. Aiming to overcome this issue, this research proposes a novel condition monitoring strategy based on the spectral energy estimation and Linear Discriminant Analysis for diagnose and identify different operating conditions in an induction motor-based electromechanical system. The proposed method involves the acquisition of vibration signals from which the frequency spectrum is computed through the Fast Fourier Transform. Subsequently, such frequency spectrum is segmented to estimate a feature matrix in terms of its spectral energy. Finally, the feature matrix is subjected to a transformation into a 2-dimentional base by means of the Linear Discriminant Analysis and the final diagnosis outcome is performed by a NN-based classifier. The proposed strategy is validated under a complete experimentally dataset acquired from a laboratory electromechanical system.

10:00
A novel methodology for broken rotor bar detection in VSD fed induction motors

ABSTRACT. This paper presents an experimental work for detection of broken rotor bar (BRB) time–frequency evolution in induction motors fed with a VSD during the startup transient and steady state. The real current of one motor phase is analyzed using the proposed technique, also is proved for synthetic signal and compared to the classic Short Time Fourier Transform (STFT) that provides a time–frequency representation, where fault related harmonics and how they evolve in the time–frequency spectrum are showed. Results shows a better detectability of the fault in the time–frequency spectrum compared with STFT, making possible to detect the BRB fault in startup transient and steady state.

10:20-10:40Coffee Break