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Distribution network reconfiguration using iterative branch exchange and clustering technique.
(2023) Pereira, Ezequiel C.; Barbosa, Carlos Henrique Nogueira de Resende; Vasconcelos, João Antônio de
The distribution network reconfiguration problem (DNRP) refers to the challenge of searching for a given power distribution network configuration with better operating conditions, such as minimized energy losses and improved voltage levels. To accomplish that, this paper revisits the branch exchange heuristics and presents a method in which it is coupled with other techniques such as evolutionary metaheuristics and cluster analysis. The methodology is applied to four benchmark networks, the 33-, 70-, 84-, and 136-bus networks, and the results are compared with those available in the literature, using the criteria of the number of power flow executions. The methodology minimized the four systems starting from the initial configuration of the network. The main contributions of this work are the use of clustering techniques to reduce the search space of the DNRP; the consideration of voltage regulation banks and voltage-dependent loads in the feeder, requiring the addition of a constraint to the mono-objective model to guarantee the transferred load will be supplied at the best voltage magnitude level, and the application of the methodology in real distribution networks to solve a set of 81 real DNRPs from CEMIG-D (the distribution branch of the Energy Company of Minas Gerais). Four out of those are presented as case studies to demonstrate the applicability of the approach, which efficiently found configurations with lower power and energy losses with few PF runs.
SHIL and DHIL simulations of nonlinear control methods applied for power converters using embedded systems.
(2018) Rosa, Arthur Hermano Rezende; Silva, Matheus B. E.; Campos, Marcos Fidelis Costa; Santana, Renato A. S.; Rodrigues, Welbert Alves; Morais, Lenin Martins Ferreira; Seleme Junior, Seleme Isaac
In this work, a new real-time Simulation method is designed for nonlinear control techniques applied to power converters. We propose two different implementations: in the first one (Single Hardware in The Loop: SHIL), both model and control laws are inserted in the same Digital Signal Processor (DSP), and in the second approach (Double Hardware in The Loop: DHIL), the equations are loaded in different embedded systems. With this methodology, linear and nonlinear control techniques can be designed and compared in a quick and cheap real-time realization of the proposed systems, ideal for both students and engineers who are interested in learning and validating converters performance. The methodology can be applied to buck, boost, buck-boost, flyback, SEPIC and 3-phase AC-DC boost converters showing that the new and high performance embedded systems can evaluate distinct nonlinear controllers. The approach is done using matlab-simulink over commodity Texas Instruments Digital Signal Processors (TI-DSPs). The main purpose is to demonstrate the feasibility of proposed real-time implementations without using expensive HIL systems such as Opal-RT and Typhoon-HL.
Analysis of the spatiotemporal MVDR filter applied to BCI-SSVEP and a filter bank extension.
(2022) Vargas, Guilherme Vettorazzi; Leite, Sarah Negreiros de Carvalho; Boccato, Levy
Artifacts inevitably permeate brain signal acquisition by electroencephalography (EEG). Hence, brain-computer interfaces based on steady-state visually evoked potentials (BCI-SSVEP) frequently require a filtering to increase signal-to-noise ratio (SNR) in an attempt to improve its ability to identify a command selected by the user. By combining the signals from different electrodes, the spatiotemporal filtering technique based on the minimum variance distortionless response (MVDR) attenuates undesired frequency components while preserving the spectral content at the visual stimuli frequencies. In this study, we revisit the MVDR filter, further evaluating its behavior with respect to critical factors in a BCI-SSVEP system: proximity amid stimulation frequencies, number of stimuli and stimulation window-length. Additionally, the main parameters of the filter were also varied, such as the order and the number of electrodes to be combined. The experimental analysis confirmed the effectiveness of the MVDR filter for the majority of the scenarios. However, it also revealed a significant difficulty that the MVDR filter has when dealing with short-length time windows, especially when compared with classical filtering techniques, such as CAR and CCA. So, in order to mitigate this limitation, we propose a filter bank MVDR (FBMVDR), where each element is a MVDR filter designed to preserve a single stimulation frequency or harmonic components. This new approach provided an increase of more than 5% in relation to the standard MVDR, reaching a performance of 92.6% in scenarios with 4 visual stimuli and 1s window-length and achieved competitive results with the state-of-the-art technique filter bank CCA (FBCCA).
Comparative performance of three phasor-extraction algorithms for co-simulation of electrical power systems.
(2021) Theodoro, Thainan Santos; Barbosa, Pedro Gomes; Tomim, Marcelo Aroca; Lima, Antonio Carlos Siqueira de
This work presents a comparison of the three phasor extraction algorithms proposed in the literature for the co-simulation of transient stability and electromagnetic transients programs. Initially, a brief mathematical review of two algorithms widely used in the literature is made: the discrete Fourier transform and the adjustment of the least-squares curve. In addition, a technique proposed by the authors based on the use of the generalized second-order integrator is presented. Then, these three techniques will be implemented and evaluated numerically through a comparative performance study extracting the fundamental phasor component of a test signal.
Power-sharing for dc microgrid with composite storage devices and voltage restoration without communication.
(2022) Bastos, Renan Fernandes; Aguiar, Cassius Rossi de; Balogh, Attila; Sütő, Zoltán; Machado, Ricardo Quadros
In this paper, we propose a new decentralized control and power-sharing strategy to manage the power flow among energy sources (ESs), energy storage systems (ESSs) and the common dc-link. In the proposed technique, we eliminate all communication among the ESSs, to reduce the complexity and increase reliability, maintaining dc-link voltage restoration. In this context, batteries and ultracapacitors (UCs) are the ESSs, while ESs can be any power source such as photovoltaic, wind, fuel-cell and etc. This technique shares the microgrid power imbalance between batteries, proportionally to their state-of-charge (SoC) and energy capacity, achieving SoC equalization. The technique also promotes voltage restoration for the UCs, keeping their average voltage constant after supplying the power peaks during power transients. For all ESSs only local variables are measured, such as local current and dc-link voltage, with no shared data between ESSs. Small signal and stability analysis are performed, along with experimental results in a lab bench show the feasibility and performance of the technique.
An auxiliary system discretization approach to Takagi-Sugeno fuzzy models.
(2022) Campos, Víctor Costa da Silva; Braga, Marcio Feliciano; Santos, Luciano Antonio Frezzatto
This paper proposes a new procedure for discretizing nonlinear systems described by Takagi-Sugeno fuzzy models. The discretization procedure consists of obtaining a linear auxiliary system that approximates the Takagi-Sugeno model over a sampling instant. By discretizing this auxiliary system, a norm bounded uncertain linear discrete-time system is found, which is capable of representing the fuzzy model. This auxiliary system, as well as the norm bounded uncertainty, is found by solving an optimization problem with Linear Matrix Inequality (LMI) constraints. To illustrate the discretization procedure, a constant state observer is synthesized based on simple LMI conditions and then applied to a real nonlinear Chua’s circuit. Additionally, a state-feedback controller based on our discretization approach is synthesized and we obtain larger maximum sampling periods than other tested strategies from the literature.
Control of event-triggered quasi-LPV systems based on an exact discretization approach - a linear matrix inequality approach.
(2022) Campos, Víctor Costa da Silva; Santos, Luciano Antonio Frezzatto; Oliveira, Tiago Gaiba de; Manzoc, Víctor Estrada; Braga, Marcio Feliciano
This paper presents an H∞ event-triggered state-feedback controller design for continuous-time non-linear systems via convex optimization techniques. The proposal is based on an exact discretization and its quasi-linear parameter varying representation. Thus, two sets of design conditions in terms of linear matrix inequalities by means of both parameter-dependent and quadratic Lyapunov functions are proposed. The proposed conditions also provide an estimate to system’s domain of attraction and an extra set of conditions is presented for a guaranteed minimum time between events. Well-known examples are employed to illustrate the effectiveness of the proposal.
Theoretical-experimental analysis of the induction generator in the use of distributed generation.
(2021) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de Almeida; Oliveira, Carlos Matheus Rodrigues de; Gomes, Luciano Coutinho
This work presents a theoretical-experimental study in permanent regime of the three-phase induction generator of squirrel cage connected directly to the distribution network at fixed speed. The study is based on the operation of the induction generator that operates with the capacitor bank and without the presence of the capacitor bank to show the improvement of the power factor of the induction generator when in connection with the electric distribution network.
Effects of harmonic pollution on salient pole synchronous generators and on induction generators operating in parallel in isolated systems.
(2020) Vanço, Wagner Eduardo; Silva, Fernando Bento; Oliveira, José Mário Menescal de; Monteiro, José Roberto Boffino de Almeida
This work presents a study of the disturbances caused by harmonic pollution in salient pole synchronous generators (SPSG) and induction generators, when operating in parallel in isolated systems. SPSG are known to operate with induction generators, since the excitation system of the synchronous generator is responsible for the voltage control on the island system. Due to the increase in the employment of power electronics, the loads take on a nonlinear behavior, where these become responsible for the generation of harmonics, due to the switching of electrical devices. Therefore, the analysis of the disturbances that these loads cause in generators, in this proposed and studied architecture, becomes essential. For the synchronous generator, there is also presented the analyses of the oscillations for voltages and currents on the dq0 model, the currents induced on the damper winding, the disturbances on the load angle and on the field current. In terms of the induction generator, the voltage and current oscillations are also analyzed from the dq0 model on the slip frequency. All the identified and quantified disturbances are oscillations on the electric variables, which possess a pulsating nature of frequencies 6ω, 12ω, and 18ω for the synchronous and induction generators, the oscillations of the sixth order and its multiples, will be given in the harmonic slip frequency of their respective harmonic orders in positive and negative sequence. In this way, verification is made as to the appearance of high slippage on the rotor of the induction generator.
A study of the effects of magnetic saturation and spatial harmonics on isolated salient-pole synchronous generators.
(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de Almeida
This article presents a study of the effects caused in isolated salient-pole synchronous generator due to magnetic saturation and spatial harmonics, these effects cause harmonic distortion in the generated voltage and current. An experimental analysis is necessary to verify the magnitude of the distortion of the generated voltage and current, focusing on which are the components generated by the non-linear constructive aspects of the salient-pole synchronous generator. The quality of generated energy depends on which harmonic components prevail in the total distortion, whether zero, positive or negative. In this way the study is based on the negative effects caused by these harmonious components of a constructive nature of the salient-pole synchronous generator.
Low-cost hardware-in-the-loop for real-time simulation of electric machines and electric drive.
(2020) Bastos, Renan Fernandes; Silva, Fernando Bento; Aguiar, Cassius Rossi de; Fuzato, Guilherme Henrique Favaro; Machado, Ricardo Quadros
This study aims to present the discrete models and the methodology to implement real-time simulations of electric machines using a low-cost digital signal processor (DSP). The DC machine and the three-phase induction machine are modelled in real-time using a Texas Instruments DSP TMS28379D, where the discrete models are implemented using C language. A minimum time-step of 1 μs can be achieved for the DC machine and 1.5 μs for the inductions machine in the experimental hardware. To validate the described models and show their precision, they are compared with commercial computational models from PSIM®. In addition, closed-loop speed control strategies are applied to the real-time DSP experimental models, showing perfect concordance with the machine theory. For the DC machine, a speed control strategy with an inner current control loop is applied and for the induction machine, a field-oriented control for the speed control. The proposed real-time simulation hardware has a great potential for low-budget research and educational purposes since it can replace a real machine setup for a very low price, with great accuracy, variable parameters and free from risks, such as accidents or equipment damage. Furthermore, it uses cheap hardware with free software and a high-level programing language.
A study of the impacts caused by unbalanced voltage (2%) in isolated synchronous generators.
(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de Almeida
This paper presents an analysis of the oscillations caused by unbalanced loads in salient pole synchronous generators that operate in isolation under steady state. The oscillatory disturbances, arising from the second-order harmonics, may have or have the potential to cause electromechanical damage to the salient pole synchronous generator. In this paper, the goal is to identify and quantify the magnitude of the electromagnetic torque, which assumes an oscillatory form due to the current component from the negative sequence, caused by unbalanced currents. The self-same analysis was included for second-harmonic voltage oscillations in the qd0 domain, the currents induced on the damper windings together with the oscillation of the load angle and on the field current. These oscillations situated on the synchronous generator are analyzed for a degree of voltage unbalance close to 2% which is an acceptable value according to international regulations for power supply from distribution networks, and this same degree of tolerated voltage unbalance will be used herein for isolated synchronous generators.
A proposal of expansion and implementation in isolated generation systems using self-excited induction generator with synchronous generator.
(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Oliveira, Carlos Matheus Rodrigues de; Monteiro, José Roberto Boffino de Almeida; Oliveira, José Mário Menescal de
This work presents a theoretical and experimental study of the self-excited three-phase induction generator in steady state, operating with a synchronous generator for use in isolated generation. Through the remoteness of many locations or because of the absence of an energy distribution network, difficulties exist in the supply of electric energy. The proposal contemplated herein can be applied in order to provide a well-adjusted voltage and reduce project costs in the expansion and implementation of isolated systems. That is, when taking into consideration acquisition costs of the asynchronous squirrel cage rotor machine in relation to the synchronous generator. The main contribution of this study is the making of the synchronous generator into a voltage regulator of the isolated system, in such a manner that the synchronous generator supplies the minimum of active power necessary, where a lower power generator is able to play the role of being the sole voltage regulator.
Space-time filter for SSVEP brain-computer interface based on the minimum variance distortionless response.
(2021) Leite, Sarah Negreiros de Carvalho; Vargas, Guilherme Vettorazzi; Costa, Thiago Bulhões da Silva; Leite, Harlei Miguel de Arruda; Coradine, Luis Cláudius; Boccato, Levy; Soriano, Diogo Coutinho; Attux, Romis Ribeiro de Faissol
Brain-computer interfaces (BCI) based on steady-state visually evoked potentials (SSVEP) have been increasingly used in different applications, ranging from entertainment to rehabilitation. Filtering techniques are crucial to detect the SSVEP response since they can increase the accuracy of the system. Here, we present an analysis of a space-time filter based on the Minimum Variance Distortionless Response (MVDR). We have compared the performance of a BCISSVEP using the MVDR filter to other classical approaches: Common Average Reference (CAR) and Canonical Correlation Analysis (CCA). Moreover, we combined the CAR and MVDR techniques, totalling four filtering scenarios. Feature extraction was performed using Welch periodogram, Fast Fourier transform, and CCA (as extractor) with one and two harmonics. Feature selection was performed by forward wrappers, and a linear classifier was employed for discrimination. The main analyses were carried out over a database of ten volunteers, considering two cases: four and six visual stimuli. The results show that the BCI-SSVEP using the MVDR filter achieves the best performance among the analysed scenarios. Interestingly, the system’s accuracy using the MVDR filter is practically constant even when the number of visual stimuli was increased, whereas degradation was observed for the other techniques.
Least-squares parameter estimation for statespace models with state equality constraints.
(2021) Ricco, Rodrigo Augusto; Teixeira, Bruno Otávio Soares
If a dynamic system has active constraints on the state vector and they are known, then taking them into account during modeling is often advantageous. Unfortunately, in the constrained discrete-time state-space estimation, the state equality constraint is defined for a parameter matrix and not on a parameter vector as commonly found in regression problems. To address this problem, firstly, we show how to rewrite the state equality constraints as equality constraints on the state matrices to be estimated. Then, we vectorise the matricial least squares problem defined for modeling statespace systems such that any method from the equality-constrained least squares framework may be employed. Both time-invariant and time-varying cases are considered as well as the case where the state equality constraint is not exactly known.
Applied sensor fusion : tuning parameters of CF and KF by means of evolution strategies.
(2020) Santos, Talysson Manoel de Oliveira; Barroso, Márcio Falcão Santos; Ricco, Rodrigo Augusto
From the point of view of metrology, inertial sensors acting separately present undesirable performance in the measurement of angular position. In order to provide measurements with greater precision and accuracy, the measures of each of these sensors are typically fused by means of filters. The performance parameters of these filters are hard to tune and several works have been using exhaustive search algorithm or manual experimental tests to tuning these parameters. However, the exhaustive search algorithm usually requires a large computational effort and adjusting parameters manually does not guarantee that the estimated parameters are optimized. In this work, it has been proposed the tuning of the Complementary Filter (CF) and the Kalman Filter (KF) through the heuristic method Evolutionary Strategies. Experimental results have shown that our method is a useful tool that considerably reduces the time to find the tuning of the FC and the FK. In addition, the use of the tuned FC and FK improved significantly metrological characteristics of the system. The use of Bland and Altman’s statistical method show that the measurements of the angular position have a good agreement with the actual angular position of a servo motor.
Cascaded interleaved DC–DC converter designed for grid-to-vehicle and vehicle-to-grid technologies.
(2021) Leal, Wagner Coelho; Bastos, Renan Fernandes; Aguiar, Cassius Rossi de; Godinho, Marcelo Oliveira; Fuzato, Guilherme Henrique Favaro; Piardi, Artur Bohnen; Braggio, Almir Augusto; Sonoda, Dabit G.; Otto, Rodrigo Bueno; Nadal, Zeno L. I.; Machado, Ricardo Quadros
This paper presents a study of a cascaded bidirectional interleaved DC–DC converter applied to an electric charging station, which uses grid-to-vehicle (G2V) and vehicle-to-grid (V2G) technologies. In this context, the interleaved technique is used to reduce the current ripple through the battery of the electric vehicle (EV), which can also absorb or deliver power to the microgrid. Additionally, the small-signal technique is also employed to calculate the gains of the PI controllers for charging and discharging the EV battery. Finally, this paper presents a set of simulations using the software PSIM® and experimental results using a low-cost hardware-in-the-loop (HIL) to support the theoretical study and to demonstrate the effectiveness of the proposed approach.
Low-cost hardware-in-the-loop for real-time simulation of electric machines and electric drive.
(2020) Bastos, Renan Fernandes; Silva, Fernando B.; Aguiar, Cassius Rossi de; Fuzato, Guilherme Henrique Favaro; Machado, Ricardo Quadros
This study aims to present the discrete models and the methodology to implement real-time simulations of electric machines using a low-cost digital signal processor (DSP). The DC machine and the three-phase induction machine are modelled in real-time using a Texas Instruments DSP TMS28379D, where the discrete models are implemented using C language. A minimum time-step of 1 µs can be achieved for the DC machine and 1.5 µs for the inductions machine in the experimental hardware. To validate the described models and show their precision, they are compared with commercial computational models from PSIM®. In addition, closed-loop speed control strategies are applied to the real-time DSP experimental models, showing perfect concordance with the machine theory. For the DC machine, a speed control strategy with an inner current control loop is applied and for the induction machine, a field-oriented control for the speed control. The proposed real-time simulation hardware has a great potential for low-budget research and educational purposes since it can replace a real machine setup for a very low price, with great accuracy, variable parameters and free from risks, such as accidents or equipment damage. Furthermore, it uses cheap hardware with free software and a high-level programing language.
Analytical upper bound for the error on the discretization of uncertain linear systems by using the tensor product model transformation.
(2020) Campos, Victor Costa da Silva; Braga, Marcio Feliciano; Santos, Luciano Antonio Frezzatto
This work provides analytical upper bounds on the discretization error of uncertain linear systems. The Tensor Product Model Transformation is used to approximate the derived discretized system, with a reduced number of vertices. Digital state feedback controllers are then designed for the discretized system, for comparison to other available work in the current literature.
Gain-scheduled control for discrete-time nonlinear parameter-varying systems with timevarying delays.
(2021) Peixoto, Márcia Luciana da Costa; Braga, Marcio Feliciano; Palhares, Reinaldo Martinez
This study addresses the gain-scheduled control problem for discrete-time delayed non-linear parameter-varying (NLPV) and linear parameter-varying (LPV) systems. First, by constructing the parameter-dependent Lyapunov–Krasovskii functional and employing multiple auxiliary functions, delay-dependent reciprocally convex inequality, and selecting a suitable augmented vector, novel delay-dependent linear matrix inequality conditions for the static output-feedback control design and state-feedback control design for delayed NLPV are provided. Second, the results obtained for discrete-time delayed NLPV systems are modified in a simple way to deal with discrete-time delayed LPV systems. Finally, the effectiveness of the proposed methods is illustrated by numerical examples.

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