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One of the most challenging hindrances to the spread use of the DC grids is their protection devices. Due to the absence of zero crossing, when a fault occurs, arc extinction becomes an issue for the traditional mechanical circuit breakers. Thanks to the recent advances in solid-state circuit breakers, this problem is solved because of the absence of mechanical contacts in their topology. However, these breakers cause not negligible conduction losses. This paper illustrates a new low-voltage bidirectional hybrid circuit breaker able to interrupt short-circuit current in few milliseconds. It provides a low-loss path for the current during the normal conduction and a fast current interruption with a limited arc level in case of fault occurrence. The working principle of the device is explained, and its functionality is proven through simulation results.

This paper evaluates the performance of modular multilevel converters with integrated battery cells when used as traction drives for battery electric vehicles. In this topology, individual battery cells are connected to the dc link of the converter submodules, allowing the highest flexibility for the discharge and recharge. The traditional battery management system of battery electric vehicles is replaced by the control of the converter, which individually balances all the cells. The performance of the converter as a traction drive is assessed in terms of torque–speed characteristic and power loss for the full frequency range, including field weakening. Conduction and switching losses for the modular multilevel converter are calculated using a simplified model, based on the datasheet of power devices. The performance of the modular multilevel converter is then compared with a traditional two-level converter. The loss model of the modular multilevel converter is finally validated by experimental tests on a small-scale prototype of traction drive.

The work focuses on hydrodynamic interactions between heaving wave energy converters (WEC). Wave parks of four devices are simulated in the time domain by a hydrodynamic-electromagnetic model, coupled with a boundary element code for the estimation of hydrodynamic parameters. Different layouts (linear, square and rhombus), WEC separation distances (5, 10, 20 and 30 buoy diameters) and incident wave directions (30° apart) are considered to assess the effect of design parameters on array power production. Then, a site-specific design optimization is carried out for different Italian locations and some key insights on wave farm design in real wave climates are provided. The results show that the effect of wave interactions on energy absorption is not expected to be a main issue, as long as the devices are separated by at least 10 buoy diameters and that the layouts are oriented to achieve the maximum energy absorption for the prevailing wave direction.

Phasor measurement units (PMUs) are expected to be the basis of modern power networks monitoring systems. They are conceived to allow measuring the phasor, frequency, and rate of change of frequency (ROCOF) of electrical signals in a synchronized way and with unprecedented accuracy. PMUs are intended to apply to three-phase systems and to track signal parameters evolution during network dynamics. For these reasons, the design of the algorithms and, in particular, of the filters that allow rejecting the disturbances while preserving the passband signal content is a paramount concern. In this paper, a novel space vector approach is proposed. It exploits the three-phase nature of the monitored signals together with proper lowpass and differentiation filters. Analytical formulas for performance prediction under almost all the test conditions prescribed by the synchrophasor standard C37.118.1 for PMUs, are introduced. The given expressions are extremely accurate, thus allowing to derive the filter design criteria for phasor, frequency, and ROCOF computation, so that the requirements in terms of estimation errors can be easily translated into filter specifications. The implications of the proposed approach in practical PMU design are illustrated by means of two simple design examples matching P and M compliance classes, respectively, for all the test cases of the standard. The reported performance proves the validity of the proposal.

Next-generation advances in stress control strategy will enable renewable energies, such as solar energy, to become more reliable and available. Critical components, such as power electronics, present uncertainties to the system control in malfunctioning process, which reduces the target of more clean energy development and CO2 emission reduction. Thus, developing and harnessing sustainable energy requires mitigating the impact of the variability of the source of energy and the impact of the adaptive stress control deployed for the proportional, integral, derivative (PID) controller to minimize the thermal stress in the power switch insulated gate bipolar transistor (IGBT). In response to this challenge, a fuzzy linear matrix inequality (FLMI) PID controller proposes initiatives for customizing parameters of PID controller corresponding to the uncertainty of IGBTs. In this paper, the uncertainty of the boost converter has been evaluated in the dynamic of the LMI model and Takagi-Sugino (TS) has applied in closed loop control to overcome the instability of the Boost converter parameters. Paper originally presented at the 5th International Conference in Through-life Engineering Services Cranfield University, 1st and 2nd November 2016.

The current grid codes for distribution networks impose on operators to provide ancillary services, like fault ride through capability and reactive power compensation. In this context, generating units with power electronics interfaces could offer as an additional service the active compensation for harmonic and interharmonic currents introduced by other converters or distorting loads. Typically, the converters of these generating units do not have information on the distortion of either other loads or of the grid current. Thus, this paper presents a control algorithm for grid harmonics and interharmonics compensation that relies only on the measurement of the voltage at the point of connection of the unit. The reference for the compensating current is calculated from the harmonic components of grid voltage in the synchronous reference frame. The paper also addresses the influence on the compensation performance of the line impedance between the generating unit and the point of connection. Experimental tests on a laboratory setup fully validate the proposed compensation method.

One of the most crucial renewable energy sources today is solar energy. Power convertors play an important role in adjusting the output voltage or current of photovoltaic (PV) systems. Using efficient and reliable switches for power converters and inverters is crucial for enhancing the safety and reliability of a platform. Generally, power converters suffer from failure mechanisms, such as wire bond fatigue, wire bond lift up, solder fatigue and loose gate control voltage, which mainly occur in power switches. In this paper, the junction temperature of the Insulated Gate Bipolar Transistor (IGBT) acting as a power switch used in the Impedance-Source DC-DC converter is estimated using an electro-thermal model in order to develop an adaptive thermal stress control (ATSC). The proposed stress control adjusts reference input of the PI control to extend the life expectancy of the device under the mission. The accuracy of results present using The Modified Coffin-Manson Law has been used to determine the life of IGBT and the lifetime has been successfully increased base on implementing imperative ATSC and comparing the result with the constant reference input of the PI controller. The result integrates with converter health management to develop advanced intelligent predictive maintenance.

This two-part paper is intended to clarify definitions in dual transformer modeling that are vague, provide accurate modeling guidelines, clarify misconceptions about numerical instability, provide a unified dual model for a specific type of transformer, and introduce new paths of research to the power systems/electrical machinery community for low-frequency transients. Part I discussed the topology of duality-based models and some important issues, such as the most common approaches to derive dual models and their variety, the equivalence of negative inductance and mutual couplings to represent the leakage inductance of three-winding transformers, and the numerical oscillations caused by the use of nontopological models. This part of the paper discusses and compares white-, gray-, and black-box models. The paper also reviews hysteresis models (static and dynamic) and highlights the differences between the air-core inductance and saturation inductance. The available dual models for the representation of the transformer tank are then presented. A unified and accurate model of a three-phase core-type transformer adequate for all low-frequency transients is presented. Finally, concrete guidelines are presented for the appropriate selection of the model topology and parameters for different low-frequency transient studies.

In order to improve the quality of steel pipes, one of the main requisites is to build pipes that are as close as possible to the designed one. To accomplish this task, an optical distance sensor of reduced size and very low power consumption was developed inside a measurement system allowing reconstruction of steel pipe dimensions. The results obtained led to the construction of a working prototype configured as an active triangulation rangefinder with a gamut of 10 cm starting at 5 cm. The characterization of the novel rangefinder has confirmed the feasibility of this new system with a resolution of $\sim 10~\mu \text{m}$ on a range of measurement of 10 cm, providing up to 10 000 measurements per second.

This Innovative Practice Full Paper presents a novel educational approach to improve the quality of graduate engineering education by emphasizing real world project based learning, the state-of-the-art and state-of-the-practice technological developments, and a need for globalization. Aiming to address the challenges of educating engineers for the 21$^{\mathbf{st}}$ Century, authors developed a double degree graduate program based on industry-university cooperation. This program includes a multifaceted-industry-university cooperation system, assuring the central role for industry as the crucial component in education of graduate level engineering students. The applied strategies and adopted methods are presented and discussed. After two cohorts of graduate students have successfully completed the program, the outcomes indicate that implemented educational approach has attained desired results. According to the survey results, students benefited significantly from the program and are in high demand by industry. The experience of this industry-university cooperation program can be valuable to other engineering schools and programs.

Purpose – The purpose of this paper is to propose a new converter topology for integrating PV plants constituted by many panels into the grid. The converter is capable of implementing MPPT algorithms on different subset of modules and can balance the different energy supplied by panels differently irradiated. The output voltage presents a very low ripple also if small filters are used for grid connection. Design/methodology/approach – In the paper, at first the converter configuration is presented. Then a control strategy for obtaining, at the same time the distributed MPPT and the power balancing on the three phases is proposed. Finally, by means of numerical simulations, the good performances of the proposed converter are shown. Findings – The proposed converter, lent from MMC configurations, is deeply studied and a suitable control strategy is well analyzed in the paper. Analytical model for voltage and current balancing are given. Research limitations/implications – The analysis presented in the paper complete some studies started in the last years and partially presented in previous scientific papers. It reaches a final point and gives all the specific for the realization of the converter and of its control. Practical implications – The paper gives all the instrument to design and realize a PV power plant integrated into building façade. Originality/value – The converter and the control for voltage and current balancing presented in this paper represent a significant original contribution of this work.

This paper deals with a low-cost diagnostic technique for polymer electrolyte membrane (PEM) fuel cells (FCs), which exploits the ripple produced by power converters to monitor the equivalent ohmic resistance. While the available literature on this topic is focused on constant-frequency control of the power converter (such as pulsewidth modulation), this paper discusses the measurement issues that arise when hysteresis current control is employed for a dc/dc boost converter, which represents the simplest solution from the implementation point of view, and therefore particularly suitable for low-cost applications. The classic frequency-domain analysis for ohmic resistance identification, based on the Fourier transform, is compared with a time-domain analysis based on a simple identification algorithm, and a real-time implementation of the latter is presented. The experimental results are obtained on a single PEM FC, but the extension to FC stacks for commercial applications is also discussed.

In this paper, a low-cost approach for polymer electrolyte membrane fuel cell (FC) drying and flooding diagnosis based on power converter ripple is presented, suitable to be implemented in commercial applications. If proper signal processing algorithms are employed, the high-frequency ripple inherently produced by switch-mode converters allows one to monitor the FC ohmic resistance, which is a good indicator for membrane drying, while an ad hoc switching control of the converter allows one to monitor also the low-frequency impedance, which is an indicator for cell flooding. This technique is tested with a dc/dc boost converter directly connected to a single cell, discussing how different FC operation modes (such as constant current or constant voltage) may affect the sensitivity required to the diagnostic algorithm to correctly recognize drying and flooding occurrences.

Nowadays, voltage transducers in medium-voltage (MV) distribution networks operate in nonsinusoidal conditions while their calibration is still based on simple sine-wave tests. A more significant characterization could be achieved using complex multitone signals. However, this requires an MV generator able to apply arbitrary voltage waveforms to the transducer under test. The authors have recently proposed a simple MV signal generator that can be effectively employed for this purpose. In this paper, the performance of this MV generator has been carefully analyzed. A characterization procedure based on multisine excitation has been proposed and tested. In particular, the main causes of uncertainty have been identified and their impact on the accuracy of the generated voltage evaluated. The analysis considers both linear and nonlinear effects, such as harmonic distortion and hysteresis.

This paper presents an energy management approach for a hybrid energy system comprised of a photovoltaic (PV) array and a polymer electrolyte membrane fuel cell (PEMFC). A single storage device, i.e., a Li-ion battery module, is used in the proposed structure. Linear proportional-integral (PI) and nonlinear flatness-based controllers for dc bus stabilization for power plants are compared. To verify the control approaches, a hardware system is realized with analog circuits for the PV, FC, and battery current control loops (inner controller loops) and with numerical calculation (dSPACE) for the external energy control loops. Experimental results with small-scale devices [namely, a PV array (800 W, 31 A), a PEMFC (1200 W, 46 A), and a Li-ion battery module (11.6 Ah, 24 V)] illustrate the excellent energy management scheme during load cycles, and the nonlinear differential flatness-based control was determined to provide improved dc bus regulation relative to a classical linear PI control method.

Analysis of failure modes and causes and diagnostic architectures are fundamental aspects for plants based on photovoltaic (PV) panel. In fact, for these plants, high level of reliability is necessary in order to operate, without failures, in the time taking into consideration also the typical lifetime of these plants. To this aim the monitoring of both plant parameters and plant performances is a very important task that can be obtained, as presented in this paper, by means of a well-designed diagnostic and monitoring system. This approach allows to improve complex system maintenance policies and, at the same time, to achieve a reduction of unexpected failure occurrences in the most critical components.

In this paper, mode conversion occurring in differential lines with cross section affected by geometric imbalance is investigated by recognizing a strict analogy with crosstalk, and by rephrasing in the modal domain the assumption of weak coupling (usually exploited for crosstalk analysis) in terms of weak imbalance. The derivation focuses on the conversion of the differential mode signal into common mode (CM) noise responsible for undesired radiated emissions, and leads to an approximate circuit model for CM-current prediction, in which the effects due to mode conversion are included by distributed voltage and current sources. Model accuracy is assessed by experimental and numerical validations involving unbalanced microstrip lines.

Salman, Ayşe (Dogus Author) The modeling of solar radiation for forecasting its availability is a key tool for managing photovoltaic (PV) plants and, hence, is of primary importance for energy production in a smart grid scenario. However, the variability of the weather phenomena is an unavoidable obstacle in the prediction of the energy produced by the solar radiation conversion. The use of the data collected in the past can be useful to capture the daily and seasonal variability, while measurement of the recent past can be exploited to provide a short term prediction. It is well known that a good measurement of the solar radiation requires not only a high class radiometer, but also a correct management of the instrument. In order to reduce the cost related to the management of the monitoring apparatus, a solution could be to evaluate the PV plant performance using data collected by public weather station installed near the plant. In this paper, two experiments are conducted. In the first, the plausibility of the short term prediction of the solar radiation, based on data collected in the near past on the same site is investigated. In the second experiment, the same prediction is operated using data collected by a public weather station located at ten kilometers from the solar plant. Several prediction techniques belonging from both computational intelligence and statistical fields have been challenged in this task. In particular, Support Vector Machine for Regression, Extreme Learning Machine and Autoregressive models have been used and compared with the persistence and the k-NN predictors. The prediction accuracy achieved in the two experimental conditions are then compared and the results are discussed.

This paper proposes an alternative test procedure for testing the radiated immunity of units and subsystems interconnected through unshielded twisted-wire pairs (TWPs). The procedure makes use of an additional wire placed in close proximity and parallel to the TWP axis to generate the interference, which is then transferred to the TWP under test through crosstalk coupling. Equivalence with field-to-wire coupling is enforced in terms of equal common mode (CM) currents induced at the TWP terminals, by resorting to the introduction of an equivalent CM straight wire to replace the original twisted line. The proposed equivalence scheme, derived by resorting to transmission-line modeling and full-wave numerical simulation, is eventually validated by measurements in the frequency interval from 1 MHz up to 1 GHz. The experiments prove the accuracy of the proposed procedure in reproducing both the CM and the differential noise induced by field-to-wire coupling in the terminations of the twisted lines.

This work reports a modeling methodology for the prediction of conducted emissions (CE) in a wide frequency range (up to 100 MHz), which are generated by dc/dc converters and propagate along the power buses of satellites. In particular, the dc/dc converter seen as a source of CE is represented by a behavioral model, whose parameters can be identified by two unit-level experimental procedures performed in controlled test setups. A simplified multiconductor transmission-line (MTL) model is developed to account for the propagation of CE in shielded bundles of twisted-wire pairs used as power cables. The whole power system is represented by the interconnection of the circuit models of dc/dc converters, cables, and Power Conditioning and Distribution Unit (PCDU). By solving the obtained network, frequency spectra of CE can be predicted. Experimental results are reported to substantiate the accuracy of the proposed unit-level dc/dc converter model and the MTL model of cables. Finally, a system-level test setup composed of three dc/dc converters connected to a PCDU is considered, and predicted CE are compared versus experimental measurements.

Attention towards power quality issues in distribution grids has increased noticeably in the last decade. Power quality assessment and monitoring require voltage transducers capable of measuring both fundamental and harmonics with adequate accuracy. Beside this, a systematic but simple procedure for evaluating the measurement performance of voltage transducers, able to quantify the impact of linear and nonlinear effects separately has not been proposed yet. In this paper, a testing method based on the concept of Best Linear Approximation (BLA) is introduced. The excitation signals resemble the voltage waveforms typically found in distribution networks, while the impact of noise and nonlinearity is evaluated in terms of sample variances. The approach is applied to the model of a typical voltage transformer by means of numerical simulations.

In a previous work, a model based on multi-conductor transmission line (MTL) theory was developed for the setup involving a tubular wave coupler (TWC) mounted in the calibration-jig. To account for the non-uniform distribution of currents and charges on the TWC metallic frames, the model parameters were estimated by resorting to an optimization procedure aimed at fitting the S-parameters measured at the ports of the calibration fixture. In view of extension of the proposed model to complex wiring harnesses, this work investigates the possibility to exploit such an MTL model to predict RF current injection onto wiring structures with geometrical/electrical characteristics different from those of the calibration fixture, without the need for re-optimizing the involved p.u.l. parameters. To this end, two parameters are identified as responsible for TWC-to-cable coupling, and specific analytical expressions and/or 2D electrostatic simulation are suggested to adapt/tune these parameters to the characteristics of the new wiring structure the TWC is clamped on. Feasibility of such an approach is assessed by comparison versus numerical simulation of an electromagnetic model of the TWC mounted on different wiring structures.

Observability of synchronous generators' dynamic parameters has significant contribution in the design of the parameter identification method of the generators. Subsequently, it has a serious impact on the accuracy level of the transient stability analysis of electrical power systems. This work is devoted to the observability analysis of these parameters in the generator dynamic performance. It has been done by introducing a sensitivity analysis concept and provides a ranking system for the generator measurements, namely the operating data, related to the observability of each parameter. It has been done using least square based indicator. These measurements consider the generator output variables such as active power, reactive power, rotor speed, rotor angle, terminal voltage and armature current. This evaluation is developed for various types of disturbances normally occur in operation of the generators, using a single-generator infinite-bus standard test system. The above ranking is performed for each type disturbance separately. These events are categorized due to change in excitation voltage, change in prime-mover torque and fault in the connected grid.

Photovoltaic (PV) energy production has become more and more important in the latest years. The need of energy efficiency pushed the research in this field both on material innovation and system management. As well known, an essential task in a PV system is performed by the tracking algorithm that has to assure the maximum power generation of the system. Many Maximum Power Point Tracking (MPPT) techniques have been defined. Among them a very promising category is that based on the modeling of the panel (model-based MPPTs). This technique allows to achieve performance comparable to that of traditional algorithms in steady state conditions. On the other side it features much higher performance from a dynamic point of view. An issue of MB-MPPTs is related to the model parameter identification and in particular to the stability of the model fitting over time. In this paper this stability problem will be analyzed for a MPPT previously proposed by the authors.

Phasor Measurement Units (PMUs) are the most modern measurement devices for electric power networks. Their performance, in terms of synchrophasor, frequency and rate of change of frequency (ROCOF) measurement accuracy are crucial for the overall performance of the network management and control applications that are expected to rely on PMU-based distributed measurement systems. In this regard, PMU performance should be assessed under different conditions. IEEE standard C37.118.1, which is particularly focused on PMUs for power transmission systems, reports tests and requirements for PMU compliance. However, some important operating conditions are neglected. In particular, the presence of unbalance in the three-phase system appears relevant for an advisable application of PMUs to distribution networks. In this paper, the impact of unbalance on two important classes of PMU algorithms is discussed. Analytical formulas are derived to estimate the effect of unbalance on synchrophasor, frequency and ROCOF estimations, and they are verified by means of numerical simulations.

Current transducers for AC power systems applications are usually calibrated by applying a sinusoidal current and comparing its output with that of a reference current transducer. Changing the excitation signal frequency, allows evaluating the frequency response function of the transducer. However, this test implies the linearity of the transducer or assumes a purely sinusoidal input during operation. Actually, for many years this is no longer representative of the actual working conditions occurring in typical distribution grids, because of the increasing penetration of power electronics, diffuse generation, nonlinear loads, etc. Hence, in order to achieve a more accurate characterization process able to consider also nonlinear phenomena, it is mandatory to investigate the behavior of current transducers with a realistic input signal. In this paper, a low-cost current generator allowing the testing of current transducers with complex excitations in the frequency band from 16 Hz to 2 kHz is presented. A metrological characterization of the proposed generator is also provided.

We are very pleased to present this special issue, which collects extended versions of the best scientific contributions presented at the IEEE International Symposium on Electromagnetic Compatibility (EMC), Signal and Power Integrity (SIPI), held in Washington, DC, USA, in August 2017. Among the novelties of this year’s edition, an “online symposium” was made available on the Internet to enable worldwide connection with the most important event of the IEEE EMC Society. In total, the symposium featured more than 180 regular papers, including oral and poster presentations. Special sessions, workshops/tutorials, panels, demonstrations, and "abstract-reviewed" papers that have an industry-oriented focus further enriched the technical program. A total number of 30 papers were selected from the regular papers and nominated for one of the three symposium awards (best EMC paper, best SIPI paper, and best student paper). We invited all the authors of these nominated papers to submit an extended version of their work. Our invitations and the subsequent peer-review process resulted in 13 accepted manuscripts. A wide range of subjects in EMC and SIPI are covered in these papers, which are grouped according to the usual categories of the IEEE Transactions on Electromagnetic Compatibility. To fulfill the high publication standard of the journal in terms of quality and significance, the authors had to include substantially new technical content beyond the symposium paper, and to place the obtained results in proper context with respect to the state of the art.

It is well known that in a photovoltaic (PV) plant, the modules are connected to switch-mode power converters to enhance the power output in every environmental condition. This task is performed by the maximum power point tracker (MPPT), which provides a current or voltage reference to the converter. Traditional perturb and observe or incremental conductance algorithms are not efficient in rapidly changing conditions, whereas a model-based (MB) MPPT offers a better dynamic performance. Because it is relatively easy to obtain an accurate model of a single PV panel, thus predicting the maximum power point voltage for given environmental conditions, MB MPPTs seemed to be attractive for employing in module integrated converters. Conventional MB MPPT algorithms, however, usually require an expensive pyranometer to properly operate. In this paper, starting from a new set of equations modeling a PV module, a novel MB MPPT technique, which does not require the direct measurement of the solar radiation, is proposed and experimentally validated.

This paper shows that in the radiated emission spectrum of high-speed railway systems, a low-frequency range exists in which the magnetic field space-frequency distribution is determined, to a large extent, by the railway infrastructure features. To prove this, electromagnetic modeling of a suitably long stretch of the railway infrastructure is developed, and an ad hoc experimental campaign is carried out for comparison. Modeling and experimental measurements refer to a 50 km stretch of the Italian 2 × 25 kV ac railway system. Infrastructure simulation is obtained by resorting to a simplified approach based on multiconductor transmission line. To this end, short segments of uniform lines are cascade-connected with lumped networks representing equipment and electrical devices placed along the line, and the radiated magnetic field is evaluated from the corresponding noise-current distributions. Since the emission source, i.e., the train, has unknown electrical properties, it is represented as a unit-current source. Thus, the proposed model provides a transfer ratio between the radiated magnetic field and the current source. As a result, the maximum values of train current corresponding to magnetic field limits provided by the International Standards can be readily derived. An optimized measurement procedure is used to show that in the frequency band 60-120 kHz, transient emissions due to random and unpredictable phenomena are negligible. In such a frequency range, where continuous and persistent emissions are present, the structure of time-frequency measurement data is readily explained, and the role of the railway infrastructure on the radiated magnetic field is unambiguously identified.

The problem of measuring current distribution in multiple-brush armatures for electromagnetic rail launchers is reapproached here to study the dynamic measurement during armature motion on a two-brush armature. The measurement method is based on an array of loops magnetically coupled to the brushes, placed along the rails. From the theoretical point of view, the measured voltages on all the loops should make possible to reconstruct the current distribution between the brushes as a function of time and armature position. This has been experimentally verified on a launcher prototype.

In this paper, immunity of differential dc power lines, recently considered as the physical layer for power line communications (PLC) onboard spacecraft, is assessed from the theoretical viewpoint. The analysis focuses on conducted immunity of the PLC channel to noise generated by the terminal units of the power line (PL). Particularly, multiconductor transmission line theory and modal decomposition are used to characterize the susceptibility of the PLC link to common mode and differential mode (DM) components of the conducted noise. Closed-form expressions for signal and noise contributions at the receiving modem are derived and used to develop design rules for the involved coupling/decoupling networks. By combining the spectral properties of the PL noise with the propagation properties of the link, it is shown that DM signaling, besides assuring a nearly flat channel frequency response, results to be more immune to the PL noise. Finally, the role that possible unbalance of the power units may play on the system conducted immunity and radiation properties is discussed by deriving analytical expressions of the longitudinal and transversal conversion loss associated with the PL terminal networks.

This paper describes an experience in transformer modeling based on open-circuit test data obtained for a wide range of terminal voltages on the low-voltage side and inrush current measurements on the high-voltage side carried out for different residual fluxes of a 300-kVA transformer. The core-type transformer model is based on a dynamic hysteresis model, which is employed individually in the legs and yokes. We start with the case where the core geometry and winding turns are known when fitting the model. The method proposed is then extended to the case where only the nameplate data and the measured no-load losses and currents are available. For this latter case, an optimization model fitting is developed.

Conventional voltage transformers (CVTs) are still widely used as transducers in power networks, thanks to their high reliability, insulation capability, low drift over time and temperature. Their rugged construction is very often used as justification for skipping periodical tests and calibrations, that require putting them off-line, thus avoiding a time-consuming and expensive procedure. For this reason, in the last years, a growing interest has been addressed towards the study of online diagnostic and calibration procedures. The typical approach is based on the frequency response analysis that permits, under sinusoidal excitation, to detect possible deterioration of the behavior of CVT. Anyway, the real interest is to check the CVT fleet already installed and operating on the grid without requiring their disconnection from the grid. As well known, distribution grid voltage features a non negligible harmonic distortion, which may allow the online evaluation of the frequency response of the transformer, by simply connecting a reference transducer. Unfortunately, being the harmonics much lower than the fundamental, this approach cannot be employed in a straightforward way because of the nonlinear behavior of the CVT. This paper proposes an innovative condition monitoring technique of CVTs based on a simplified Volterra model. This opens the way to a new approach to the on-site characterization of CVTs, exploiting the actual voltage of the grid and thus not requiring its disconnection.

The integration of renewable energies in the context of distribution networks has brought a number of issues that are the subject of study and research. In order to experimentally analyze the behavior of these issues, test systems are needed, that can be easily replaced by Power Hardware in the Loop devices. This article will present the basics of hardware in the loop co-simulation using Simulink and Arduino in order to shed light on these issues. Just to address the highlighted problems, a new architecture based on a Real Time dSPACE Board and an inverter, is presented. The architecture implemented lends itself to different simulations of different complexity. In this article, the system will be used to simulate a photovoltaic system consisting of a module, an inverter and is closed on a load. The ability to have information in digital format and to have simulated elements, allows the study of intelligent systems, such as the smart distribution networks.

In this paper the development of a new design solution for high-current shunt resistors is presented, which allows achieving very good accuracy while requiring a simple and low-cost manufacturing process. It is based on a solid cylinder having the voltage measurement circuit which runs through two holes drilled in the cylinder itself. Starting from the well-known expression of the current density in a cylindrical conductor, the frequency response of the shunt is obtained in closed form as a function of the geometric parameters. In turn, the positions of the voltage measurement terminals are chosen by optimizing the frequency response function over a specified range. A shunt prototype has been manufactured and its measurement performance has been evaluated. The experimental results confirm the validity of the approach and highlight the significant improvement with respect to the single-hole cylindrical shunt which has been recently proposed by the authors. The obtained measurement accuracy is noticeable when compared with the ease of manufacturing.

Phasor measurement units (PMUs) are the key measurement devices of modern power networks monitoring systems. The high accuracy and fast reporting rates required for PMU implementations ask for improvements in both hardware and software solutions. Depending on the characteristics of the monitored voltages and currents, the accuracy of PMU algorithms may represent the main contribution to the overall measurement performance. For this reason, research is ongoing in the field of signal processing techniques for phasor and frequency estimation. In this context, Interpolated Discrete Fourier Transform (IpDFT) is one of the most interesting techniques, mainly because it allows accurate measurements under off-nominal frequency conditions while preserving simplicity and computational efficiency. In this paper, the applicability of IpDFT to three-phase signals that are typical of power networks is discussed. Then, it is proposed to combine the advantages of IpDFT with those of the Space Vector approach for positive sequence synchrophasor and frequency measurements.

This study explores and theoretically assesses the possibility to eavesdrop information from differential interconnects by resorting to sensing loop(s) placed in proximity and suitable signal processing algorithms. Time-domain crosstalk in the terminations of the loops, operating as hardware Trojans, is the coupling phenomenon exploited to reconstruct the transmitted digital signals. This investigation proves that—even though geometrical and electric characteristics of the emitting interconnect are not perfectly known—the original digital signal can be successfully reconstructed. To this end, three different methods and related algorithms are proposed and compared in terms of 1) reconstruction accuracy, 2) involved computational burden, and 3) flexibility in the design of the sensing loop(s). Effectiveness of the proposed algorithms (whose fundamentals are derived in free space) in the practical case of inhomogeneous media (i.e., presence of dielectric substrate) is assessed by full-wave numerical simulation of a virtual setup, in which the emitting and receiving pairs are realized as microstrip printed circuit board lands.

This paper investigates the injection of RF energy onto wiring harness using a tubular wave coupler (TWC). In particular, a transmission line (TL) model of a commercial TWC mounted in the calibration fixture provided by the manufacturer is developed. The proposed model of the calibration setup provides accurate prediction of the measured insertion loss up to 2 GHz. Measurement data and outcomes of three-dimensional electromagnetic simulation of the TWC are used to obtain estimates of some of the involved model parameters, whose direct evaluation is not possible due to partial knowledge of the geometrical/electrical characteristics on the one side, and nonuniform distribution of current and voltage on the TWC cross section on the other. The proposed TL model is used to explain the fundamental phenomena responsible for RF-energy transfer through the TWC. Particularly, it is shown that, differently from bulk current injection probes where inductive coupling is the dominant phenomenon, injection through the TWC involves both inductive and capacitive coupling. This determines a certain amount of directivity of the injection device, and is expected to play a role in RF injection onto complex cable bundles.

This work investigates the mechanism of generation of undesired common-mode (CM) currents in differential-line interconnects with slight non-uniformity owing to imperfect production process. To this end, three different non-ideal configurations are considered, obtained by perturbation of an ideally-uniform differential interconnect composed of two microstrips. By resorting to modal analysis, the governing transmission line equations are written as a perturbation of those of the ideal structure. This allows circuit interpretation of the mode conversion phenomenon in the analogy with crosstalk. The role played by each geometrical parameter (varying along the line) on the frequency response of the common- and differential-mode quantities induced at the line terminals is shown and discussed.

In a previous work, the possibility to eavesdrop digital signals transmitted along differential interconnects was explored by resorting to sensing loop(s), operated as hardware Trojans placed in close proximity of the data lines. To maximize coupling, ideal (i.e., symmetric) positioning of the receiving loop(s) with respect to the differential interconnect was considered. However, since in practice misalignment between the two circuits may occur, this work investigates robustness of the eavesdropping algorithms to possible geometrical deviations from the ideal (symmetric) configuration. Here, the objective is to assess accuracy of the proposed methods in reconstructing the original waveforms even in case of nonideal positioning of the receiving loop(s).

This paper investigates the performance of an automotive RKE (Remote Keyless Entry) system under the influence of RF interference, injected by the Bulk Current Injection (BCI) test technique. Measurements indicate a severe degradation of performance in the 15 MHz–30 MHz frequency band where RF current injection level is set at 106 dBμA. Injection at these frequencies leads to failure in correct operation of the RKE system. The analysis clearly shows that such a failure is due to the interaction of the BCI sinusoidal current waveform with non-linear devices in RKE electronics, giving rise to non-negligible harmonics in the passband of the RF receiver. Computational electromagnetic simulation (CST EMC Studio) is used to cross check the experimental measurements.

We demonstrated a continuous-wave laser using an anti-reflection coated Cr2+:CdSe crystal with transmission of 98 % at wavelength range from 2.0 to 2.7 μm and with relatively large laser damage threshold of 30 MW/cm2 for the first time. A maximum output power of 1 W at wavelength 2450 nm with an optical-optical efficiency of 48 % and a slope efficiency of 50 % was obtained when the incident pump power was 2.1 W.

Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC) and Fiber Reinforced Cementitious Composites (FRCCs) plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in the aforementioned field all over the last lustrum will be reviewed. A method based on the measurement of the inductance of a probe to be placed on the specimen will be presented and its progressive development will be described. Obtained correlation with actual fiber dispersion, as checked by means of destructive methods, as well as with the mechanical performance of the composite will also be presented, in an attempt to address the significance of the method from an engineering application perspective.

Conducted emissions (CE) generated by the inverter and propagating along the high-voltage dc power bus in electric vehicles are predicted via a circuit model implemented in SPICE. Through extensive simulations, the impact of different functional operating points (in the typical torque-speed characteristic used to drive the motor) is put in evidence. Additionally, the role of radio-frequency noise propagation in the shielded cables of the dc power bus (electrically long at the wavelengths of interest) is investigated.

This paper proposes a new design solution for high-current shunt resistors aiming at optimizing the frequency response in a specified frequency range. It is based on a solid cylindrical shunt, whose sensing circuit runs through a straight hole drilled in the shunt itself. Compared to other solutions proposed in the literature, typically based on coaxial or cage configurations, this approach allows a more compact size, a simple mathematical modeling of the current distribution due to skin effect (therefore less complex mathematical solution of the optimization problem) and a cost-effective manufacturing process. Experimental results obtained from a shunt prototype are reported, which confirm the validity of the proposed approach.

Synchronized measurements of electrical signals' phasors and frequencies are expected to be fundamental in the monitoring and management of future power systems, in particular in the so-called smart grid scenario. In fact, Phasor Measurement Units are conceived as the key elements of advanced wide area monitoring systems. For these reasons, the design of measurement algorithms able to track amplitude, phase angle and frequency dynamics has been receiving increasing attention in the last years. The Kalman filter, together with a dynamic phasor model, is seen as a promising tool in this context. In this paper, a Taylor Extended Kalman filter formulation that considers the amplitude and phase angle Taylor expansion separately is introduced. A new dynamic model is defined to allow reducing the state space dimension while including also harmonics in a simple way. The performances of the algorithm in terms of both fundamental and harmonic components measurement accuracy are investigated by simulation, considering nonstandard tests inspired by the regulatory norms for distribution systems.

This paper proposes an optimal charging strategy for plug-in electric vehicles (PEVs) to be used in electric distribution networks. The optimization algorithm is made up of two phases: 1) an optimal power flow calculation; and 2) a linear optimization. The former, while taking into account the power system technical constraints, sets the upper bounds to the recharge power for each vehicle and the latter defines the recharge profiles of each PEV. In order to test the effectiveness of the optimization algorithm, a case study was set up. The connection of 300 PEVs to the Conseil International des Grands Reseaux Electriques (CIGRE) European low voltage benchmark network has been simulated. The proposed algorithm has been compared with a nonoptimal charging strategy, which assigns a flat charging profile by dividing the energy requested by the desired recharge time. The results show that the optimization algorithm both complies with the energy requests set by the end users and with the technical operation limits of the network. This allows for PEVs to provide a basic-although of paramount importance-service to the grid: the smart charge.

This paper introduces a new control strategy to realize a virtual synchronous generator. The proposed control strategy is based on virtual impedance and band-pass damping algorithms to achieve the electro-mechanical characteristics of synchronous generator for the grid converter. Differences between new and traditional method on impedance emulation, and differences between traditional pure proportional damping algorithm and new band-pass damping algorithm are discussed as well. Additionally, detailed analysis of the components of synchronous generator is given, also the roles of the various parts of synchronous generator in the power system stability control are explained. The behavior of designed control strategy is validated by both simulations and experiments made on a 2kW grid-connected inverter.