L.s. Barros

• Doctor of Engineering
• Professor (Associate) at Federal University of Paraíba

Distributed Energy Resources (DERs) integration into distribution systems becomes problematic when the penetration level exceeds the system DER hosting capacity. Although several studies propose to quantify DER hosting capacity, methodologies to maximize it in distribution systems are scarce. Some approaches propose installing var compensators, inc...

Since photovoltaic (PV) represents a vast part of microgrid generation, its no power reserve feature requires battery energy storage systems (BESS) to provide frequency and voltage support in islanded mode. Control strategies have been developed to allow it, however, tests have not considered the impact of unbalanced loads, even less for microgrids...

Photovoltaic generation does not have the capacity to compensate imbalances between generation and load demand, which can occur in islanded operation of microgrids and cause voltage and frequency deviations. Thus, battery energy storage systems are inserted to support microgrid regulation, what constitutes the hybrid generation units. In these unit...

The increased integration of photovoltaic (PV) systems to distribution networks can cause several problems for the system operator. If the distributed generation hosting capacity (DGHC) of the network is exceeded, some power quality limits, such as reverse power flow in substation, undervoltage and overvoltage, will also be exceeded. The reactive p...

Photovoltaic (PV) in low-voltage distribution systems (LVDS) becomes problematic when the penetration level exceeds system photovoltaic hosting capacity (PVHC), since it leads to violations of power quality constraints. Maximizing PVHC enables customer service expansion by allowing more power from prosumers and load attendance. Although several wor...

In modern power systems, transmission over long distances and offshore wind energy conversion systems increasingly use the technology of high voltage direct current transmission due to cheaper investment costs, lower power losses, and better controllability. However, effective integration of this technology drastically reduces the overall system’s...

The real-time digital simulation (RTDS) of electrical networks is an important analysis tool, with applications in the operation, design, planning and expansion of electrical systems. To make RTDS viable, it is necessary to perform a computational modeling of the electrical network components and their characteristics, from energy generation and di...

In microgrids based on photovoltaic/battery generation, uncertainties during islanded operation can cause voltage and frequency fluctuations, making the control systems involved in the microgrid more difficult to action. From the photovoltaic maximum power point tracking (MPPT) point of view, to reduce the effects of uncertainties it is necessary t...

Microgrids based on photovoltaic array supplying do not have capacity to compensate imbalances between generation and load demand, which can occur in islanded operation and cause voltage and frequency deviations. Therefore, battery energy storage systems are inserted to help in microgrid regulation. Grid-forming droop control is applied for PV/batt...

The concept of autonomous microgrids has strongly increased due to the large penetration of distributed generation into the main grid, mainly photovoltaic systems. Attached to these generation units, Battery Energy Storage Systems (BESS) has been widely used to support voltage and frequency regulation since it provides a fast system response. There...

Distributed generation (DG) based on synchronverter with no battery is unable to provide frequency support without compromising DC-bus voltage level. However, this paper proposes a new synchronverter, which can outline this limitation by adjusting the DC-bus voltage setpoint if the grid frequency gets out of a safe predefined range. This is done th...

The voltage margin control strategy is often used for multi-terminal high voltage direct current (MTDC) transmission systems. It ensures a tight regulation of DC voltage similarly to the master–slave and sharing of voltage regulation task between two or more stations similar to the voltage droop, therefore combining desired features of those contro...

This paper proposes a novel fault current suppression method for doubly fed induction generator (DFIG) low voltage ride through (LVRT) improvement employing modular multilevel converter (MMC). It is based on the inherent MMC arm impedance and the number of levels to provide transient damping of DFIG rotor and stator currents under severe grid fault...

This paper presents an analysis of the anti-islanding protection (AIP) functions behavior during the islanded operation of a distribution network section that contains simul- taneously distributed generators interfaced by inverters and directly connected to the grid via synchronous generator. Through the simulations carried out, it was verified tha...

Real-Time Digital Simulation (RTDS) is a powerful tool in modeling and analyzing electrical and drive systems because it provides an efficient and accurate process. There are several hardware devices for this type of simulation; however, their high costs have led to the increasing use of more affordable and reconfigurable technologies. In this cont...

The occurrence of faults in multi-terminal high voltage direct current (MTDC) systems is a critical situation for both control and protection systems. For instance, MTDC systems work under large overcurrents during DC faults due to the discharging of capacitors on the DC side and the feeding of AC fault current to the DC system via the converters'...

Electricity generation with low inertia offers operational risks due to the high frequency gradients in the face of network disturbances providing solutions to this problem is a major challenge today in such a way that this work presents a heuristic method to tune controllers that provide frequency support, through the concept of synthetic or virtu...

In this study a application proposal to develop a classifier using an artificial neural network (ANN) for the problem of detecting internal faults in a wind turbine generator based on an induction machine with a caged rotor, a problem for which there is still no optimal solution. The classifier evaluates a given instance and returns whether the ins...

New grid-connected systems have imposed additional requirements regarding reliability, power quality, high levels of power processing capacity, and fault support, where power converters have a crucial role in fulfilling these requirements. Overcoming one of these challenges, this paper proposes a new alternative application to improve the low-volta...

Squirrel cage induction generator is a low cost and robust alternative for grid-connected variable speed wind energy conversion systems. For maximum power point tracking of these systems, conventional vector control strategies may face some difficulties such as: model parameter uncertainties, variable reference and cross-coupled disturbances. Adapt...

Many control strategies for grid-interfacing voltage source inverter (VSI) of distributed generation (DG) units have been reported for grid support, among them virtual synchronous machine (VSM) techniques, in particular the Synchronverter which has the ability to operate in voltage and frequency support mode, in active and reactive power control mo...

A alta integração da geração distribuída baseada em Fontes renováveis (GD-FER) no sistema elétrico convencional aumenta preocupação associada com a confiabilidade da rede e a qualidade da energia gerada. Assim, muitas estratégias de controle do conversor fonte de tensão (VSI) têm sido reportadas para o suporte à rede pela GD-FER, dentre as quais as...

A microgrid consists of a grid capable of operating in connection to the main interconnected power system or in island mode. This paper deals with a microgrid containing a small hydroelectric power plant (HPP), a battery energy storage system (BESS), a wind energy conversion system (WECS), and a photovoltaic array (PV). The WECS and PV systems are...

The advancements in power electronics have supported the widespread penetration of wind energy conversion systems (WECS) in electric grids. In this context, power converters have crucial functionality in the control of active and reactive power injection, moreover they are directly related to voltage and current harmonic distortion levels, mechanic...

Because of the high penetration of distributed generation (DG) systems based on renewable energy sources (RES), it is necessary to develop control techniques for improving support to grid frequency and voltage from this kind of generation. Among the solutions proposed in the literature, the virtual synchronous generator (VSG) concept has proven to...

This paper proposes a method that combines the Adaptive Perturb and Observe (Adaptive P&O) and Simulated Annealing (SA) optimization approaches to identify the global maximum power point in photovoltaic (PV) modules. This identiffication is critical to enable that such modules can deliver their maximum power to the utility network, considering diff...

The high integration of distributed generation (DG) system based on renewable energy sources (RES) in the power system requires changes regarding the control mode of these sources with some urgency. Such changes seek to maintain the stability of the power systems. Thus, there is a demand for using control techniques on DGs/RESs that can mitigate th...

Nowadays, power converters play a fundamental role in the conditioning and processing of active and reactive power, and are directly related to power quality indexes. In this sense, new multi-level converter topologies have been integrated in order to provide higher power processing capacity with lower harmonic distortion, switch stress, heating, a...

Due to the increasing penetration of Renewable Energy Sources (RES) such as wind energy in electrical grids, Wind Energy Conversion Systems (WECS) participation in primary control is becoming required including the Doubly Fed Induction Generator (DFIG)-based WECS. High integration of large scale DFIG-based WECS brings new challenges to their primar...

High voltage direct current (HVDC) systems are an alternative for transmission of energy with higher efficiency and lower electrical losses over long distances. HVDC systems have become more common with the evolution of power electronics, promoting the interest of research in power flow control techniques. The main objective of this paper is to per...

A necessidade de matrizes energéticas mais sus-tentáveis por meio da diminuiçdiminuiç˜diminuição do uso de combustíveis fósseis e a expansão da oferta de energia elétrica por fontes renováveis estão favorecendo a ampliaçampliaç˜ampliação de novas tecnologias tal como a geraçgeraç˜geração eólica. Neste contexto, a estabilidade da frequênciá e peça c...

For maximum power point tracking of squirrel-cage induction generator-based wind energy conversion systems, control strategies may face some difficulties such as: unmodeled dynamics, variable reference and disturbances. Adaptive controllers may offer good reliability and robustness against these issues, for these reasons, in this work a model refer...

This paper investigates the response to grid disturbances of the wind energy conversion system based on the doubly fed induction generator (DFIG-based WECS). It is proposed a new control termed as heightened statefeedback control structure (HSFC) with predictive behavior to regulate the rotor current loops, which is able to effectively counteract t...

For Wind Energy Conversion Systems (WECS) based on Permanent Magnet Synchronous Generators (PMSG) with back-to-back converters, some strategies have been employed aiming safe and reliable grid-connection, among them the grid-side control in coordination with the braking chopper. Conventionally, the grid-side control is of the Proportional-Integral...

Devido à crescente participação da energia eólica nas redes elétricas, códigos de rede de muitos países requerem que sistemas de conversão de energia eólica permaneçam conectados durante afundamentos de tensão, entregando potência e participando do controle dos níveis de tensão da rede. Para turbinas eólicas baseadas no gerador síncrono de ímã perm...

Atualmente, dentre as topologias de sistemas de conversão de energia eólica (SCEE), as baseadas em conversores de potência plenos estão em crescimento, uma vez que este tipo de conversor permite a operação da máquina em largas faixas de velocidade, o que resulta em um melhor aproveitamento da potência disponível no vento. Para este tipo de aplicaçã...

This work presents a methodology developed for dynamic wind generation simulation connected to an electric power system. It presents wind generators models and rotor excitation control strategies. The turbine mechanical power is obtained from the wind speed × time characteristic in combination with turbine power curve. The methodology has been appl...