Ricardo Quadros Machado

University of São Paulo | USP · Departamento de Engenharia Elétrica e de Computação (SEL) (São Carlos)

Low-voltage grid-connected microgrids rely on the exploitation of inverter-interfaced distributed energy resources (DERs) in order to feed loads and to achieve bidirectional power flow controllability at their point of common coupling (PCC) with the upstream grid. However, adverse operational conditions, such as the existence of DERs of different o...

To correct the frequency and voltage deviations in the buses of an islanded AC microgrid (MG), generated by the droop control, and to achieve precision in the reactive power sharing between the distributed generation (DG) units, this work proposes a distributed fuzzy consensus secondary controller (FCSC), composed by a fuzzy controller (FC) in asso...

The DC–DC converters usually interfaces renewable energy sources in DC microgrids which may be contaminated by harmonic perturbations that adversely affect performance, creates stability and protection problems in a DC grid system. In this paper, the authors propose the use of the popular proportional–integral–derivative (PID) controller to mitigat...

Formerly in the literature, a new interleaved-based boost converter was devised for multiple input voltage sources purposes. Nevertheless, when only a single input voltage source is connected to the 2-phase version of this converter, it can be seen as a compact interleaved boost with voltage multiplier (cIBVM). A brief description of cIBVM operatio...

This paper presents a method for Energy Storage Systems (ESSs) equalization and energy management in dc microgrids (MGs) with slow dynamic sources, such as Fuel Cells (FCs). The three main features of this method are the ESSs equalization, the energy management between the ESSs and the FC, and the ability to suppress fast transients of load, preven...

The intermittent characteristics of microgrids (MGs) have motivated the development of energy management systems (EMSs) in order to optimize the use of distributed energy resources. In current studies, the implementation of an EMS followed by experimental-based analyses for both grid-tied and stand-alone MG operation modes is often neglected. Addit...

A common method for load sharing is using frequency and voltage droop controllers because there is no need to have communication links in the microgrid. However, the droop control strategy has a drawback, that is, it imposes voltage and frequency deviations, which can be fixed by adding a secondary control loop. On the other hand, if the microgrid...

This paper presents a new methodology to manage the initialization process of fuel cells (FCs) as a main source in a micro-grid. The startup aims to reduce the warming-up time, increase the FC efficiency and decrease the time response. As solution, the use of storage systems (SSs) combined with an adaptive gain-scheduling to absorb the power transi...

The connection of distributed generation systems powered by fuel cells (FCs) to the grid requires power electronics devices with high voltage gain, high capability of power processing and high levels of current absorbed from the direct current (dc) source. In this context, the authors propose the use of an interleaved boost with voltage multiplier...

This paper presents a five-level active-neutral-point-clamped converter applied as a single-phase shunt active power filter that can be used in low and medium voltage systems aiming a harmonic filtering and reactive power compensation generated by nonlinear loads in which the current control strategy is based on the Synchronous Reference Frame. Two...

Este artigo tem por objetivo apresentar a topologia de um conversor multinível aplicado como filtro ativo paralelo (FAP) para sistemas de baixa e média tensão no qual é empregado como técnica de compensação o método fundamentado no sistema de referência síncrona (Synchronous Reference Frame - SRF), visando a compensação de distúrbios como correntes...

Este trabalho apresenta uma estratégia de compensação ativa de potência de forma seletiva, de forma a gerar as correntes harmônicas de referência, que são utilizadas na malha de controle de um filtro ativo de potência paralelo monofásico com um conversor multinível ANPC 5 níveis. É possível através da estratégia seletiva, escolher quais componentes...

In this paper we propose a new decentralized control strategy applied to a DC Microgrid in order to manage the power delivery of storage devices into a common DC-link, avoiding high-bandwidth communication (HBC) between the storage devices (SD) and alternative sources. Batteries and Ultracapacitors (UC) are used as SD and the common DC-link is fed...

The present paper addresses the AC microgrid control issue using the hierarchical control structure and droop controllers for load sharing. Once the droop controllers impose an operation with frequency and voltage deviations, depending on the load and droop parameters, a hierarchical control structure must be added to change the droop controller op...

The present work addresses the AC microgrid control issue using hierarchical control structure and droop controllers for load sharing. Once the droop controllers impose an operation with frequency and voltage deviations, depending on the load and droop parameters, a hierarchical control structure must be added to change the droop controller operati...

In this paper we present a new approach to obtain pointwise Thevenin equivalents from electrical measurements of non-linear sources. The classical technique to obtain the Thevenin equivalent can not find equivalent circuits of nonlinear sources. Using pointwise Thevenin equivalents it is possible to obtain equivalent circuits for non-linear sources...

Email Print Request Permissions This paper presents an automated system applied to a dc machine used to the emulation of aerodynamic torque of a distributed generation power plant. The experimental arrangement proposed aims to avoid the wind turbine dependence of climatic variations. In order to evaluate the proposed approach, we presented a set of...

Print Request Permissions This paper presents an analysis of impacts caused by out-of-phase automatic reclosing in grid connected distributed generation systems. The automatic reclosing is the reconnection of a feeder in case a fault is established. Out-of-phase reconnection can damage the utility and customer equipments. Two scenarios are discusse...

The connection of renewable energy sources to the grid, in a way that characterizes distributed generation, enables the optimization of local available natural resources. These sources should be managed in order to produce a distortion-free AC terminal voltage, and to inject in the grid the power that is not consumed by the local load. In the syste...

This study presents a control strategy for managing power delivered to, or absorbed from, the grid, independent of local load or grid characteristics. To achieve this objective, the strategy requires the use of three levels of control structures. The first is related to phase-locked loop and grid-tie algorithms, which are employed to minimise distu...

In this paper, a fuzzy proportional derivative and/or a classical proportional integral is used to control the terminal voltage of the photovoltaic (PV) array connected to the input of a dc/dc step-up converter. The voltage reference is tracked continuously by employing a perturb and observe and the incremental conductance algorithms in order to ma...

This study proposes a method for islanding detection in distributed generation systems, namely, hybrid fuzzy positive feedback (PF). The aim is to reduce the injection of disturbances during the grid-connected operation from the anti-islanding methods, particularly at the instant of load connection and, do not require adjustment of the PF gain and...

This study proposes an islanding detection method for distributed generation systems, namely frequency fuzzy positive feedback (FFPF).The goal is to reduce the injection of disturbances, from the anti-islanding methods, during the grid-connected operation, as well as standardise the PF gain, with no adjustments needed according to the type of loads...

The operation of distributed generation systems (DG) is subjected to events such as unintentional islanding occurrences. To prevent the activation of the DG's protections and power supply interruption, when an islanding occurs, the DG must change from grid-connected operation mode to isolated operation mode and keep the voltage and the frequency wi...

A fuzzy ${{hbox {P+}}{hbox {I}}}$ and a classical proportional-integral (PI) controllers for charging and discharging of a battery pack connected to a photovoltaic (PV) array are described. To maintain the PV array operating as close as possible to the maximum power point (MPP) a perturb and observe (P&O) algorithm along with a classical PI control...

This paper presents the application of fuzzy controllers to act in the current control loop of a shunt active power filter (SAPF). The SAPF consists of a three-phase inverter with four-leg topology, and it has been used to reduce the harmonic content produced by nonlinear loads, as well as, in the reactive power compensation. The generation of the...

This paper presents a strategy to control the terminal voltage produced by the voltage source inverter (VSI) as well as, the power delivery or absorbed from the grid independently of the local load. The terminal voltage is controlled by means of double cascade PI controllers. The resonant controller is placed in parallel to the classical voltage PI...

The objective of this study was to characterize a collection of 19 Brachiaria brizantha accessions, obtained from the International Center of Tropical Agriculture (CIAT), Colombia, and preserved in the germplasm bank of the Pasture and Forage Research Station of Cascajal, Cuba. A total of 17 (13 quantitative and 4 qualitative) international descrip...

The objective of this study was to characterize a collection of 19 Brachiaria brizantha accessions, obtained from the International Center of Tropical Agriculture (CIAT), Colombia, and preserved in the germplasm bank of the Pasture and Forage Research Station of Cascajal, Cuba. A total of 17 (13 quantitative and 4 qualitative) international descrip...

The objective of this study was to characterize a collection of 19 Brachiaria brizantha accessions, obtained from the International Center of Tropical Agriculture (CIAT), Colombia, and preserved in the germplasm bank of the Pasture and Forage Research Station of Cascajal, Cuba. A total of 17 (13 quantitative and 4 qualitative) international descrip...

The study was conducted at the Pasture and Forage Research Station < >, in order to determine the morphological characteristics of Gliricidia sepium, as well as the bromatological composition and sugar proportion in its flowers. Twenty of 165 G. sepium trees were sampled, which represented 12% of the total, and each tree constituted a replication....

The study was conducted at the Pasture and Forage Research Station «Indio Hatuey», in order to determine the morphological characteristics of Gliricidia sepium, as well as the bromatological composition and sugar proportion in its flowers. Twenty of 165 G. sepium trees were sampled, which represented 12 % of the total, and each tree constituted a r...

This paper presents a design procedure and a control strategy for a grid-connected single-phase multilevel converter. The proposed system uses two series connected H-bridge modules, one fed by photovoltaic panels, the other by energy storage devices. The former switches at line frequency, while the latter operates in PWM. The system is designed to...

This paper presents a study to reduce the positive feedback gain in Anti-islanding detection methods based on frequency positive feedback. The main idea is to reduce the injection of disturbances at the point of common coupling (PCC) during the grid-connected operation. This proposal refers to the closed-loop frequency adjustment of the synchroniza...

This paper proposes a management strategy for a diesel generating set (GS) covering the mechanical part of the system which includes speed and active power control, the electrical part of the system which includes voltage and reactive power control, and the synchronism with the grid. The management is based on a fuzzy PD+I controller structure whic...

The research was conducted at the Pastures and Forages Research Station "Indio Hatuey" in order to determine the organoleptic, physical and chemical characteristics of the honey produced by Melipona beecheii. For the extraction and packaging of the honey; sterile syringes and dry sterilized flasks, properly labeled, were used. After that, in the sa...

El objetivo de este trabajo fue determinar el comportamiento de 19 accesiones de Panicum maximum en suelos de mediana fertilidad. Se utilizó un diseño de bloques al azar con tres repeticiones y parcelas de 20 m2. Las rotaciones (pastoreo racional simulado) se efectuaron entre 60 y 70 días (época de seca) y entre 32 y 40 días (época de lluvia). Se d...

A prospecting mission was conducted in order to identify and collect species of the natural and naturalized forage flora, distributed on a ferromagnesian reddish Brown Fersialitic soil of the Rafael Freyre municipality, Holguin. Three plant formations were taken into consideration: (A) non-anthropic thorny brushwood, (B) semi-anthropic savannas and...

A prospecting mission was conducted in order to identify and collect species of the natural and naturalized forage flora, distributed on a ferromagnesian reddish Brown Fersialitic soil of the Rafael Freyre municipality, Holguín. Three plant formations were taken into consideration: A) non-anthropic thorny brushwood, B) semi-anthropic savannas and C...

This paper proposes a fuzzy control strategy for both stand-alone and grid-connected operations of a diesel generating set (GS). The GS fuzzy controller designed for stand-alone operation is presented first, followed by the fuzzy approach for grid-connected operation, in which the terminal voltage and reactive power controllers are coordinated to r...

This paper proposes a fuzzy voltage and frequency positive feedback (PF) for islanding detection in distributed generation system (DG). The proposed method is based on positive feedback in dq synchronous frame and the design methodology of the fuzzy detection is based on fuzzy inference rules. The main idea is to reduce the injection of disturbance...

The study was conducted at the Pasture and Forage Research Station < >, in order to determine the morphological characteristics of Gliricidia sepium, as well as the bromatological composition and sugar proportion in its flowers. Twenty of 165 G. sepium trees were sampled, which represented 12% of the total, and each tree constituted a replication....

The research was conducted at the Pastures and Forages Research Station "Indio Hatuey" in order to determine the organoleptic, physical and chemical characteristics of the honey produced by Melipona beecheii. For the extraction and packaging of the honey; sterile syringes and dry sterilized flasks, properly labeled, were used. After that, in the sa...

A prospecting mission was conducted in order to identify and collect species of the natural and naturalized forage flora, distributed on a ferromagnesian reddish Brown Fersialitic soil of the Rafael Freyre municipality, Holguin. Three plant formations were taken into consideration: (A) non-anthropic thorny brushwood, (B) semi-anthropic savannas and...

El objetivo de este trabajo fue caracterizar dos procedencias introducidas desde Suramérica (Planta-2 y Planta-3) y tres colectadas en Cuba (SSCS-5, Colón-1 y Las Tunas), de Ricinus communis L. Para ello se consideraron indicadores morfológicos y agroproductivos. Se utilizaron parcelas de 40 m2 (área vital), con diez plantas. El diseño fue totalmen...

The objective of the work was to study the effect of storage under ambient conditions on the germination of seeds from Leucaena leucocephala cv. Cunningham subject to partial hydration. The treatments were: control, no scarification (T0); thermal scarification (TS) with H2O at 80ºC, for two minutes (T1); TS plus partial hydration, on tray with tap...

Resumo— Neste trabalho é proposto um sistema de controle fuzzy experimental para a regulação de tensão de saída de um conversor CC-CC elevador de tensão utilizado como interface entre uma fonte CC e o link CC de conversores multiníveis. O controle fuzzy empregado foi desenvolvido de forma que ele pudesse ser embarcado em um processador do tipo DSP...

On a low-fertility, acid soil (pH ~ 4,9), a collection of 20 Brachiaria brizantha accessions associated to Stylosanthes guianensis CIAT-184 was studied, in order to evaluate its agronomic performance during the establishment stage. For such purpose, 5 x 4 m plots were used, with three replications. The measured and/or estimated indicators were: sur...

Nowadays, the Brazilian electric systems need the development of new researches and tools, in order to obtain a logic solution to maintain and improve the reliability and the quality of the power delivered to customers. Therefore, the study of the appropriate connection of dispersed generation sources is an essential topic to be analyzed, since thi...

The objective of the work was to study the effect of storage under ambient conditions on the germination of seeds from Leucaena leucocephala cv. Cunningham subject to partial hydration. The treatments were: control, no scarification (T0); thermal scarification (TS) with H 2O at 80°C, for two minutes (T1); TS plus partial hydration, on tray with tap...

The objective of this work was to characterize two provenances introduced from South America (Planta-2 and Planta-3) and three provenances collected in Cuba (SSCS-5, Colon-1 and Las Tunas), of Ricinus communis L. For such purpose, morphological and agroproductive indicators were considered. Plots measuring 40 m 2 (vital area) were used, with ten pl...

The objective of the work was to study the effect of storage under ambient conditions on the germination of seeds from Leucaena leucocephala cv. Cunningham subject to partial hydration. The treatments were: control, no scarification (T0); thermal scarification (TS) with H 2O at 80°C, for two minutes (T1); TS plus partial hydration, on tray with tap...

The objective of this work was to characterize two provenances introduced from South America (Planta-2 and Planta-3) and three provenances collected in Cuba (SSCS-5, Colon-1 and Las Tunas), of Ricinus communis L. For such purpose, morphological and agroproductive indicators were considered. Plots measuring 40 m 2 (vital area) were used, with ten pl...

In this paper, a fuzzy PD plus a PI controller structure for a photovoltaic PV system is presented. The controller tracks a voltage reference given by the perturb and observe P&O maximum power point tracking (MPPT) algorithm. The main drawback of the P&O MPPT algorithm is that at steady state the operating point oscillates around the maximum power...

This paper provides experiences of the international project BIOMAS-CUBA in the implementation of energy supply alternatives from biomass in rural areas, which are compatible to food security and environmental sustainability. These experiences are comprised between 2009 and 2011, within the agroenergetic farm concept, and are related to research an...

Maximum power point tracking (MPPT) techniques are used to achieve the maximum output power of a photovoltaic (PV) system. Although there are many MPPT techniques, perturb and observe (P&O) method is the most commonly used. This paper shows the improve of MPPT P&O performance even with rapidly changing irradiance conditions by applying a feedback c...

This paper provides experiences of the international project BIOMAS-CUBA in the implementation of energy supply alternatives from biomass in rural areas, which are compatible to food security and environmental sustainability. These experiences are comprised between 2009 and 2011, within the agroenergetic farm concept, and are related to research an...

This paper provides experiences of the international project BIOMAS-CUBA in the implementation of energy supply alternatives from biomass in rural areas, which are compatible to food security and environmental sustainability. These experiences are comprised between 2009 and 2011, within the agroenergetic farm concept, and are related to research an...

This paper proposes a different method of power quality disturbance classification combining discrete wavelet transform (DWT), principal component analysis (PCA) and neural networks. This method associates properties from the multiresolution-analysis (MRA) technique with standard deviation and average calculation to extract the discriminating featu...

This paper presents a controlled power converter for three-phase grid connected systems. When the power converter operates connected to the grid the current/power is used as control variable. However, if the power converter is operating in stand alone mode (on contingency or islanding mode) the control variable must be changed to voltage. Finally,...

Recent advances in energy technology generation and new directions in electricity regulation have made distributed generation (DG) more widespread, with consequent significant impacts on the operational characteristics of distribution networks. For this reason, new methods for identifying such impacts are needed, together with research and developm...

The objective of this work was to create a methodology of interactive keys from the reconstruction of published text keys. The general key of the book "Árboles de Cuba" (Trees from Cuba), in which the technique of building text keys through the traditional method is explained, was used as a model; in this book there are important tree and shrub gen...

In order to evaluate the growth dynamics of 24 accessions of the genus Brachiaria spp., this study was conducted in the Barrancabermeja region, Santander, Colombia. A completely randomized design was used, in 72 plots of 21 m2 each and three replications (plots) for each treatment. The accessions were grouped according to the growth habits into: st...

This paper presents a comparative analysis about the influences of three inverter-based distributed generators control modes on several important aspects of distribution networks. The control modes investigated are constant current, constant reactive and active power, and constant voltage and active power. The investigated aspects are steady-state...

The objective of this work was to determine and quantify the species that are part of the flora diversity in eight livestock production or integral farms, linked to the Local Agricultural Innovation Center of Matanzas. For that purpose, a systematic sampling design was used; the sample size was not lower than 0,5%. In general, there was high divers...

The objective of this work was to determine and quantify the species that are part of the flora diversity in eight livestock production or integral farms, linked to the Local Agricultural Innovation Center of Matanzas. For that purpose, a systematic sampling design was used; the sample size was not lower than 0,5%. In general, there was high divers...