Connected operator

This paper focuses on control strategies of Microgrid which consists of wind turbines, photovoltaic panels, batteries and super-capacitors with Hybrid DC and AC Buses. In grid-connected operation, voltage of DC bus is kept steady by inverter and voltage and frequency of AC bus are the same with utility grid. Energy Management System controls hybrid storage system to release or absorb power with the strategies according to grid condition, state of charge of batteries and super-capacitor, electricity price and so on. In islanded operation, voltage of DC bus is controlled by storage system and amplitude and frequency of AC-Bus voltage are regulated by parallel inverters with voltage-frequency or droop control strategy. In this paper, different control strategies in grid-connected and islanded operation are described which can keep power balanced and AC/DC bus stable. Simulation and experimental results are shown to verify the proposed control method.

This paper presents a new sensorless method for the vector control of doubly-fed induction machines (DFIMs) without using speed sensors or rotor position measurements. The proposed sensorless method is based on the model reference adaptive system (MRAS) estimating the rotor position and speed from the machine rotor currents. The method is appropriate for both stand-alone and grid-connected operation of variable

This paper describes the series connection of integrated gate commutated thyristors (IGCTs) using RC-snubbers. An experimental setup with a power rating of 6 kV, 4 kA is used to analyze the dynamic and static behavior of the series connected IGCTs in detail. The mechanism of thermal stabilization of series connected IGCTs is discussed. It is shown that a good voltage

This article discusses a new experimental way to measure the I-V characteristic curve of photovoltaic (PV) generators based on DC-DC converters. The obtained results show that the classical buck and boost converters are not capable of reproducing the whole I-V curve of PV generators and that the single-ended primary inductance converter (SEPIC) is optimal for this application. We propose a method based on SEPIC converters in parallel connection, operating in an interleaved mode. This method gives advantages with respect to the use of conventional methods.

Connectivity, the characterising feature of the Internet, requires the definition of access prices, transit charges, among connected operators. However, for many information exchanges, the network hierarchies in the Internet are not fixed: two providers can be simultaneously supplier and retailer, in a routing process, while being horizontally competitors in another. We study the impact of interconnection with transit demand on prices and profits for Internet Service Providers. These effects crucially depend on the degree of differentiation of the retail sector.

This article discusses a new experimental way to measure the I-V characteristic curve of photovoltaic (PV) generators based on DC-DC converters. The obtained results show that the classical buck and boost converters are not capable of reproducing the whole I-V curve of PV generators and that the single-ended primary inductance converter (SEPIC) is optimal for this application. We propose a method based on SEPIC converters in parallel connection, operating in an interleaved mode. This method gives advantages with respect to the use of conventional methods.

The Image Foresting Transform (IFT) reduces optimal image partition problems from seed pixels into a shortest-path forest problem in a graph, whose solution can be obtained in linear time. It has allowed a unified and efficient approach to edge tracking, region growing, watershed transforms, multiscale skeletonization, and Euclidean distance transform. In this paper, we extend the IFT to introduce two connected operators: cutting-off-domes and filling-up-basins. The former simplifies grayscale images by reducing the height of its domes, while the latter reduces the depth of its basins. By automatically or interactively specifying seed pixels in the image and computing a shortest-path forest, whose trees are rooted at these seeds, the IFT creates a simplified image where the brightness of each pixel is associated with the length of the corresponding shortest-path. A label assigned to each seed is propagated, resulting a labeled image that corresponds to the watershed partitioning from markers. The proposed operators may also be used to provide regional image filtering and labeling of connected components. We combine the cutting-off-domes and filling-up-basins to implement regional minima/maxima, h-domes/basins, opening/closing by reconstruction, leveling, area opening/closing, closing of holes, and removal of pikes. Their applications are illustrated with respect to medical image segmentation.

This paper deals with a class of morphological operators called connected operators. These operators filter the signal by merging its flat zones. As a result, they do not create any new contours and are very attractive for filtering tasks where the contour information has to be preserved. This paper shows that connected operators work implicitly on a structured representation of the image made of flat zones. The max-tree is proposed as a suitable and efficient structure to deal with the processing steps involved in antiextensive connected operators. A formal definition of the various processing steps involved in the operator is proposed and, as a result, several lines of generalization are developed. First, the notion of connectivity and its definition are analyzed. Several modifications of the traditional approach are presented. They lead to connected operators that are able to deal with texture. They also allow the definition of connected operators with less leakage than the classical ones. Second, a set of simplification criteria are proposed and discussed. They lead to simplicity-, entropy-, and motion-oriented operators. The problem of using a nonincreasing criterion is analyzed. Its solution is formulated as an optimization problem that can be very efficiently solved by a Viterbi (1979) algorithm. Finally, several implementation issues are discussed showing that these operators can be very efficiently implemented

This paper focuses on the energy management system and stability of DC bus in both grid-connected and islanded operations in microgrid system. The microgrid system consists of wind turbines, photovoltaic panels, batteries and super-capacitors, also includes both AC and DC zones. Voltage of DC bus must be kept stable especially in islanded operation. In grid-connected operation voltage of DC bus is controlled by inverter. Real power from renewable energy generations and storage system can be transferred to AC zone through DC bus. In islanded operation, inverter must be controlled to keep magnitude and frequency of AC bus stable, so storage system is used to regulate voltage of DC bus. Simulation results in the paper show that voltage of DC bus can be kept steady and power can be kept balance with the strategy in microgrid system.

We present a review of software-induced failures in commercial nuclear power plants (NPPs) and in several non-nuclear industries. We discuss the approach used for connecting operational events related to these failures and the insights gained from this review. In particular, we elaborate on insights that can be used to model this kind of failure in a probabilistic risk assessment (PRA) model. We present the conclusions reached in these areas.

We give in this paper which is the third in a series of four a theory of covariant derivatives of representatives of multivector and extensor fields on an arbitrary open set U ⊂ M, based on the geometric and extensor calculus on an arbitrary smooth manifold M. This is done by introducing the notion of a connection extensor field γ defining a parallelism structure on U ⊂ M, which represents in a well-defined way the action on U of the restriction there of some given connection ∇ defined on M. Also we give a novel and intrinsic presentation (i.e. one that does not depend on a chosen orthonormal moving frame) of the torsion and curvature fields of Cartan's theory. Two kinds of Cartan's connection operator fields are identified, and both appear in the intrinsic Cartan's structure equations satisfied by the Cartan's torsion and curvature extensor fields. We introduce moreover a metrical extensor g in U corresponding to the restriction there of given metric tensor g define...

In this paper a multiscale study based on the use of morphological connected transformations is presented. In particular, the morphological opening and closing by reconstruction are used as connected transformations. These transformations have the characteristic of preserving contours without introducing new information, in addition to smoothing the processed image as the size of the structuring element increases. Due to this, both connected filters and the identity are used as primitives to introduce two operators that allow a multiscale treatment to the processed image in accordance with the scale parameter. The multiscale morphological operators are called opening–closing by reconstruction and closing–opening by reconstruction, respectively. In the case of the opening–closing by reconstruction transformation, the propagation of extrema when the structuring element enlarges has an interesting behavior. In addition, the fingerprints of the image given as a function of regional maxima, regional minima and scale parameter are defined. Finally, the proposals of this work are illustrated with some examples.

This paper presents a control strategy of a hybrid fuel cell/battery distributed generation (HDG) system in distribution systems. The overall structure of the HDG system is given, dynamic models for the solid oxide fuel cell (SOFC) power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between the fuel cell power plant and the battery energy storage, a neuro-fuzzy controller has been developed. Also, for controlling the active and reactive power independently in distribution systems, the current control strategy based on two fuzzy logic controllers has been presented. A Matlab/Simulink simulation model is developed for the HDG system by combining the individual component models and their controllers. Simulation results show the overall system performance including load-following and power management of the HDG system.

The Image Foresting Transform (IFT) reduces optimal image partition problems from seed pixels into a shortest-path forest problem in a graph, whose solution can be obtained in linear time. It has allowed a unified and efficient approach to edge tracking, region growing, watershed transforms, multiscale skeletonization, and Euclidean distance transform. In this paper, we extend the IFT to introduce two connected operators: cutting-off-domes and filling-up-basins. The former simplifies grayscale images by reducing the height of its domes, ...

... 1, JANUARY 2008 Sensorless Control of Doubly-Fed Induction Generators Using a Rotor-Current-Based MRAS Observer Rubén Peña, Member, IEEE, Roberto Cárdenas, Senior Member, IEEE, José Proboste, Greg Asher, Fellow, IEEE, and Jon Clare, Senior Member, IEEE ...