The increasing installed area of solar technologies around the world gives us an idea about the unlimited potential available in solar energy. This combined with the rising fossil fuel prices and frequent power outages, favor decentralized power generation among domestic consumers and small industries. However, the low energy of the solar PV module, the low exergy of the solar flat plate thermal collector and limited usable shadow-free space on building roof-tops could be overcome by the high overall (electrical and thermal) efficiency of a solar Photovoltaic Thermal (PV/T) system, which combines the electrical and thermal components in a single unit area. This paper gives a brief overview of the different solar flat plate PV/T technologies, their efficiencies, applications, advantages, limitations and research opportunities available.

Flat plate solar photovoltaic–thermal (PV/T) systems : A reference guide

For the last ten years, at least three different special sections dealing with diagnostics in power electrical engineering have been published in the IEEE transactions on industrial electronics [1]-[5]. All of them had their specificities, but the last ones, starting in 2011, were more connected to relevant events organized on the topic. In fact, these events have been clearly the only international forums fully dedicated to diagnostics techniques in power electrical engineering. For this particular issue, it has been decided to separate the different submissions into six parts: state of the art; general methods; induction machines (IMs); synchronous machines (SMs); . electrical drives; power components and power converters. The second section includes only one state-of-the-art paper, which is dedicated to actual techniques implemented in both industry and research laboratories. The third section includes three papers on diagnostic techniques not specifically aimed at a particular type of machine. The fourth section includes three papers devoted to diagnostics of rotor faults, two dedicated to stator insulation issues, and four papers dealing with mechanical faults diagnosis in IMs. The fifth section includes papers focusing on different types of SMs. The first two papers deal with wound-rotor SMs, the following three papers are dedicated to permanent-magnet radial flux machines, and the last one deals with permanent-magnet axial flux machines. Regarding the types of faults analyzed, there are three papers devoted to the diagnosis of interturn short circuits in the stator windings, i.e., one dedicated to the detection and location of field-winding-to-ground faults and a paper devoted to the diagnosis of static eccentricities. In the sixth section, two papers investigate issues related to faults in drive sensors, and one is devoted to fault detections in the coupling inductors. The last section includes two papers devoted to diagnosis of faults and losses analysis in switching components of power converters.

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Modern Diagnostics Techniques for Electrical Machines, Power Electronics, and Drives

Ease of integration of the variable speed diesel generators resulting in substantial reduction of the fuel consumption is the key motivation for the development of the dc shipboard power system (SPS). One of the impediments to the widespread adoption of the dc SPS, however, has been the lack of comprehensive fault management strategies during the short-circuit faults. Such strategies comprise of fault detection, fault isolation, and reconfiguration of dc SPS. In the existing literature, all these aspects of fault management are dealt independently and mostly assuming ideal conditions. All the strategies are of utmost importance and it is needed to study them under a common framework which is the aim of this paper. This paper starts with a brief discussion on the characteristics of dc SPS along with recent modeling techniques. Subsequently, this paper describes the short-circuit fault studies, fault characteristics, and protection requirements. Finally, this paper outlines the working principle, advantages, and limitations of the fault detection, isolation, and reconfiguration strategies developed for the dc power system and analyzes their suitability to the dc SPS. This paper is concluded by identifying the future research trends needed for the development of the short-circuit fault management strategies of dc SPS for critical marine missions.

Short-Circuit Fault Management in DC Electric Ship Propulsion System: Protection Requirements, Review of Existing Technologies and Future Research Trends

WFSM are included in the majority of large power generating units and special high-power motor drives, due to their high efficiency, flexible field excitation and intrinsic flux weakening capability. Moreover, they are employed in a wide range of high-end solutions in the low-to-medium power range. This contribution presents a comprehensive survey of classical and modern methods and technologies for excitation systems (ESs) of (WFSMs). The work covers the fundamental theory, typical de-excitation methods and all the modern excitation equipment topologies in detail. It also includes a description of the state-of-the-art and the latest trends in the ESs of wound-field synchronous motors and generators. The purpose of the paper is to provide a useful and up-to-date reference for practitioners and researchers in the field.

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Excitation System Technologies for Wound-Field Synchronous Machines: Survey of Solutions and Evolving Trends

This special section on "Diagnosis and Prognosis for Complicated Industrial Systems—Part II” is the continuation of its previous part I (IEEE Transactions on Industrial Electronics, Vol. 63, Issue 4, 2016). The diagnosis and prognosis approaches can be roughly classified into two categories: 1) model-based and 2) data-driven approaches. The model-based approaches perform the diagnosis and prognosis relying on the physical models from first principles, whereas the data-driven approaches make full use of the process data to monitor the systems under consideration. Due to the increasing complexity of the industrial system, new challenges are encountered in diagnosis and prognosis of such complicated systems, and more efficient process monitoring approaches are needed. From this point of view, the papers included in this section are focused on the recent developments of diagnosis and prognosis for complicated industrial systems, providing novel ideas and referential directions for both the academic and industrial communities.

Diagnosis and Prognosis for Complicated Industrial Systems—Part II

In order to achieve total selectivity at electrical distribution networks it is of great importance to analyze the defect currents at ungrounded power systems. This information will help to grant selectivity at electrical distribution networks ensuring that only the defect line or feeder is removed from service. In the present work a new selective and directional protection method for ungrounded power systems is evaluated. The new method measures only defect currents to detect earth faults and works with a directional criterion to determine the line under faulty conditions. The main contribution of this new technique is that it can detect earth faults in outgoing lines at any type of substation avoiding the possible mismatch of traditional directional earth fault relays. This detection technique is based on the comparison of the direction of a reference current to the direction of all earth fault capacitive currents at all the feeders connected to the same bus bars. This new method has been validated through computer simulations. The results for the different cases studied are remarkable, proving total validity and usefulness of the new method.

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New selective earth faults only current directional method for isolated neutral systems

This paper presents results about the influence of rotor capacitance in the on-line rotor ground fault location method for synchronous machines with static excitation. The location method is based on the measurement of the voltage in a grounding resistance, connected to the neutral of the excitation transformer. Due to the effect of the rotor capacitance to ground on large synchronous generators, it is observed that waveform of the neutral voltage is perturbed, and it causes an error in the fault location in case of defect in the DC side. Firstly, the influence of the fault resistance value and the fault position is evaluated through computer simulations. Then, the impact of the rotor capacitance in the accuracy of the detection and location method is analyzed in case of ground fault, as well as in healthy operating condition.

Influence of rotor capacitance in on-line rotor ground fault location method for synchronous machines with static excitation

This paper presents the theoretical approach and experimental tests of a new algorithm for detecting ground faults in rotor windings of synchronous generators with static excitation. This location method requires the installation of a grounding resistance in the secondary winding of the excitation transformer. First, the third-harmonic reference voltage is obtained by the voltage measurements in the excitation system. Then, the third-harmonic voltage at the grounding resistor is compared to the reference voltage. The ground fault is detected when the phase angle between those voltages is under the trip setting value. This new algorithm has been tested in a 5 kVA Synchronous generator with satisfactory results.

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Improvement of the ground-fault detection in field windings of synchronous machines with static excitation based on third-harmonic voltage phase-angle comparison

The correct coordination of the electrical protections of a synchronous generators is a difficult task, especially those based on impedance. Usually, these protections are set according to the recommendations of the main standards and manufacturer guides. However, the validation of the settings is difficult to obtain, since there is no commissioning test to evaluate the correct selectivity. In this paper, the use of SIMSEM power-system simulation software is proposed to evaluate the settings of a turbo-generator. Firstly, three electrical protections based on impedance characteristics are described. Secondly, a case study is presented with some simulations results. Finally, the advantages of using this procedure in the engineering process of power plants.

Coordination of a turbo-generator protections through power-system simulation software SIMSEN

Generator differential protection is one of the most important electrical protections of synchronous generator. Its operation principle is based on the comparison of the input current and output current at each phase winding and it allows the trip when the currents are not similar. In many cases, a false differential current causes unwanted trip commands as a result of the saturation of current transformers (CTs). In this paper, the proposed criterion can identify whether it is an external fault or an internal fault in the protection zone and it allows preventing trip commands which have been caused by the saturation of the CTs.

F. R. Blanquez

Papers

New selective earth faults only current directional method for isolated neutral systems

Influence of rotor capacitance in on-line rotor ground fault location method for synchronous machines with static excitation

Improvement of the ground-fault detection in field windings of synchronous machines with static excitation based on third-harmonic voltage phase-angle comparison

Coordination of a turbo-generator protections through power-system simulation software SIMSEN

Improvements to generator differential protection based on the criterion of signs of the DC-component