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Random Pulse Width Modulation (RPWM) allows controlling the switching signal of power converters in order to reduce the harmonic peaks by spreading the noise spectrum. Currently, many manufacturers of power converters are deploying this modulation scheme in order to comply with Electromagnetic Compatibility (EMC) test requirements. However, when the converters coexist with Power Line Communication (PLC) systems, such as in Smart Grid (SG) applications, resorting to RPWM needs further investigations since it potentially affects the communication channel by increasing the bit error rate. This possible detrimental effect is investigated in this work, by considering a PLC system for automatic meter reading (AMR) implemented in a SG application. To this end, the model of a complete PLC system is implemented in SIMULINK, and Quadrature Phase Shift Keying (QPSK) modulation is used to model the PLC modems in the communication channel. Results show that, even if the deployment of RPWM techniques may lead to an appreciable reduction/spreading of the peaks in the noise spectrum, it may also lead to an increase of the bit error rate on the PLC system.

In the development of alternative test methods for pre-compliance radiated-susceptibility (RS) investigations, it is proven that a special test setup, involving an additional wire placed in proximity of the cable under test and fed by two radio-frequency generators, can reproduce through crosstalk (XT) the same terminal voltages/currents induced in the standard RS test setup, on condition that those generators are properly controlled in magnitude and phase. Such a test setup does not require expensive facilities like anechoic chambers and powerful amplifiers to feed antennas, therefore it represents a fast and cheap alternative to get feedback on radiated immunity in the early-design stage, before the formal RS assessment carried out according to standards. While in past literature works the equivalence between XT and RS was demonstrated for some simple cables like a single bare wire or a differential pair, this paper presents a new XT-based test setup suitable for the practically relevant case of a complex bundle of dielectric-covered wires. To this aim, two different formulations of feeding conditions are proposed, one more rigorous, based on multiconductor-transmission-line modeling, and one approximate, based on bundle-reduction techniques. The performance of both the equivalence schemes is assessed and discussed in the frequency range between 1 MHz and 1 GHz.

This work investigates the performance of RF immunity procedures exploiting semi-rigid coaxial test probes as coupling devices to inject continuous wave (CW) RF power into the outlets of Integrated Circuits (ICs). Two solutions are presented, both offering the advantage with respect to the traditional direct power injection method, to run the test without removing the IC from its actual PCB. The first procedure resorts to near-field coupling to inject the noise into an interconnecting trace. The second procedure requires metallic contact between the probe tip and the injection point (e.g., a via or an IC pin). Specific figures of merit, such as coupling and power efficiency, test repeatability and intrusiveness, sensitivity to setup parameters and lateral spatial resolution, are introduced and used to ascertain the effectiveness of the proposed procedures. To this end, both numerical simulations and measurements were carried out on several PCBs. Feasibility of the proposed immunity procedures is eventually proven by an application example, involving a thermal sensor as device under test.

Harmonic distortions are going to be more important in the near future due to widespread employing of power electronic based devices. The quality of power may get degraded without using proper mitigation methods. On the other hand, new paradigms of deregulated markets which make the power a competitive product as well as customer inclinations to pay for a high-quality power, inspire distribution companies to enhance the power quality level. Hence, various investigations should be considered to meet the power quality standards in electric networks. In this paper, a market-based framework is proposed for central management of harmonic compensation actions in microgrids (MGs). Since distributed energy resources (DERs) are prevalent in MGs, the compensations actions could be based on DERs activities in addition to conventional active power line conditioners (APLCs). Hence, a detailed investigation of harmonic filtering capabilities of various DERs is firstly represented. Afterward, a global model is proposed for various harmonic active power filters (APFs) either based on DERs or APLCs. To comply with the obligations of deregulated power markets, a new concept named as harmonic power market (HPM) is proposed for economic management of various APF resources participating in harmonic mitigation actions. Furthermore, a distortion power expexted payment function (DEPF) is introduced for each APF participating in the HPM. The HPM framework is modeled as an optimization model subject to various standards, technical and systematic constraints implemented in some case studies. Simulation results show the capability and performance of the proposed model for optimal management of various APF resources in harmonic compensation. Increasing in harmonic filtering capability, deferring the requirements for installation of new APLCs as well as a decrease in harmonic compensation costs are the main advantages of using DER based APFs in the HPM.

Current transformers for ac power systems applications are usually calibrated by applying sinusoidal currents at different frequencies. The main limitation of this approach is that it does not take into account nonlinearities that may have a significant impact on harmonic current measurement. A more accurate characterization should be based on test currents that are similar to those found in normal working conditions. However, this demands a proper current generator able to generate multitone waveforms with proper accuracy, which is seldom available in laboratories. This paper proposes a simple approach to implement a current generator, based on a waveform generator, a power amplifier, and a transformer which allows boosting the output current capability. Its uneven input–output response can be compensated through linear prefiltering of the desired current waveform. When the generator is employed to reproduce a specific class of current waveforms, such as those typically found in ac distribution grids, an optimal compensation filter can be easily designed. This approach allows canceling systematic nonlinearities introduced by the transformer and the power amplifier, thus significantly increasing accuracy with respect to a conventional frequency response compensation, as confirmed by experimental results.

Black-box modelling approaches, based on suitable sets of measurements at the output ports of the device, are often exploited for the modelling of power converters to predict their conducted emissions. However, these techniques can be effectively applied only if the device to be modelled can be approximately treated as a linear and time-invariant (LTI) system. This assumption is not necessarily satisfied by every power converter. In order to investigate suitable conditions assuring effectiveness of black-box modelling for a boost converter, this work investigates the role that the converter input capacitors and the functional inductor play in masking the inherent non-linear and time variant behavior of the switching modules, and their impact on the effectiveness of the proposed black-box model. It will be shown that preliminary measurements of the differential mode impedance of the converter can provide useful information on the feasibility of black-box modelling techniques, even in the absence of detailed information on the internal architecture of the converter.

The measurement of harmonics is essential in modern power systems in order to perform distortion level assessment, disturbances source detection and mitigation, etc. In this context, the role of Instrument Transformers (ITs) is crucial, as they are key elements in every power systems measuring instrument. However, inductive ITs, which are still the most widely used, suffer from both a filtering behavior due to their dynamics and from nonlinear effects due to their iron core. The target of this paper is to deeply analyze the performance of two digital signal processing techniques, recently proposed in literature, aimed at mitigating their nonlinear behavior: they are SINDICOMP and the compensation of harmonic distortion through polynomial modeling in the frequency domain. Their performance in improving the measurement of voltage harmonics are analyzed through numerical simulations, by adopting waveforms that can be typically encountered in power systems during normal operating conditions., "This project 19NRM05 IT4PQ has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme". Funder name: European Metrology Programme for Innovation and Research (EMPIR) Funder ID: 10.13039/100014132

Power electronic converters represent a pillar of modern power systems, especially since generation from renewable energy sources, such as photovoltaics, have been introduced. One of their main characteristics consists of the high flexibility in converting different voltage levels and waveforms. As for all the conversion devices, they are subjected to unavoidable losses introduced by non-ideal components. For this reason, in the last few decades numerous research activities have been devoted to model their behavior and predicting the global efficiency. In spite of the number of scientific publications on the topic, the non-idealities have been rarely studied in terms of their impact on the input-output characteristics of the converter. In this paper, the conventional equivalent circuit of a step-up DC/DC converter has been upgraded in order to introduce the effects of both conduction and switching losses. The obtained formulation, applicable to all DC/DC converters, allows a more accurate average model that is particularly suitable for the study of multi-converter architectures, as for the most recent renewable energy sources applications. Finally, thanks to a dedicated test setup, the results of an experimental campaign demonstrate how the new formulation faithfully predicts its electrical behavior.

Conventional current transformers (CTs) suffer from nonlinearities due to their ferromagnetic cores. On one hand, it is well-known that severe core saturation may occur because of large overcurrents or unidirectional transient components: this may substantially impact the operation of relays. On the other hand, weaker nonlinear effects are also present during regular working conditions. In particular, the spectral content of typical current waveforms is characterized by a strong fundamental term responsible for harmonic distortion affecting the frequency components at the secondary side. In turn, this has a significant impact on the accuracy that can be reached as long as current harmonics must be monitored. The target of this work is implementing a simple signal processing technique that allows compensating for this effect. The method, characterized by extremely low computational complexity, is first introduced and validated using numerical simulations. After this, it was tested experimentally to improve the harmonic measurement capability of inductive CTs. The achieved results highlight a noticeable reduction of errors at low-order harmonics over a wide range of primary current amplitudes. It is worth noting that the black-box approach makes the technique suitable also for compensating nonlinearities introduced by current transducers based on different operating principles. Thanks to this peculiarity and to the low computational complexity, the proposed method is suitable to be employed in power quality analyzers and merging units. In this way, high-accuracy monitoring of current harmonics in power systems can be achieved, opening the way to advanced power quality management and to the location of disturbing users.

Modern distribution networks are characterized by higher distortion and wider variability of voltages and currents. Accurate synchrophasor, frequency and ROCOF measurements thus ask for new techniques trying to reduce latency while limiting the impact of spurious components. Taylor-Fourier Multifrequency approach is a good candidate for Phasor Measurement Units intended for distribution system applications. In this paper, an improved version of this method is proposed, relying on the potentialities carried by window functions in both support identification and estimation. Its potentialities are assessed through non-standard test conditions, confirming the enhanced accuracy.

The number of nonlinear devices in distribution grids has rapidly grown in the last years, and this trend is likely to increase in a near future. In this scenario, power quality monitoring and identification of disturbance sources are critical aspects. Inductive transformers are often employed for this purpose, although their metrological performances are guaranteed only near rated frequency. Secondary voltage harmonics are affected by the filtering behavior of the transformer, but also by nonlinearities due to the iron core that may have remarkable impact. In this work a novel post-processing technique allowing to dramatically reduce the detrimental effects of nonlinearities is proposed and discussed. After explaining the methodology, it has been applied to enhance the harmonic measurement accuracy that can be obtained by using an inductive medium voltage instrument transformer. Experimental tests carried out in laboratory show the significant performance improvement achieved thanks to the proposed approach.

This paper investigates the beneficial effects of Random Modulation strategies in reducing the conducted emissions generated by DC-DC converters. The analysis is carried out by PSpice-Simulink co-simulation in order to achieve effective modelling of the converter on the one hand (PSpice), and easy implementation of the modulation scheme on the other (Simulink). Particularly, Random Pulse Width Modulation is used to control a DC-DC converter involving second-generation Cree SiC MOSFET. The non-linear characteristics of the converter as well as its parasitic elements are considered by the PSpice model. The predicted CM and DM emissions are compared versus those obtained by standard PWM, showing a significant reduction of the overall emissions in the frequency range of interest.

In this paper, a perturbative technique and the related computational algorithms are presented for the prediction of differential mode (DM) to common mode (CM) conversion arising from asymmetry and nonuniformity in differential interconnects. It is shown that discontinuities evolving from nonuniformities and geometrical imbalance along the (usually desired uniform) lines give rise to equivalent distributed sources that couple the (ideally decoupled) DM and CM circuits. The prediction of modal quantities is then achieved numerically, as an iterative perturbative refinement of the frequency response of an ideal differential line. Different levels of approximation are introduced and discussed. Specifically, the assumption of weak imbalance allows analyzing the propagation of the two modes separately. Moreover, the assumption of weak nonuniformity allows avoiding CM refinements. The proposed technique applies to both ideally uniform and inherently nonuniform interconnects, and leads to a significant simulation speed-up compared to traditional approaches that analyze nonuniform lines by their subdivision into uniform sections. The methodology is illustrated based on two differential microstrip lines, one tapered and one with sinusoidally varying trace edges. Validation against full-wave simulations and measurements is provided.

Effective design of active filters for specific applications poses several challenges to EMC engineers. If on the one hand, the theoretical considerations available in the literature are complete and exhaustive, on the other hand, when moving to actual filter implementation, some practical considerations on the final application are mandatory. The first aspect to be carefully accounted for regards the actual source and load impedances of the system where the filter is installed. Concerning this, it will be proven that not only the impedance magnitude but also the phase plays a significant role, since disregarding it may lead to undesired oscillations, noise amplification or saturation of the electronics. Also, the non ideal behavior of the involved circuitry has to be considered when predicting the insertion loss of an active EMI filter. An enhanced circuit model of the filter is proposed and its effectiveness for the prediction of the filter insertion loss is proven by measurements on a common mode active filter in the frequency interval from 10 kHz up to 108 MHz.

This article introduces a modulation technique for modular multilevel converter (MMC) in variable speed traction drives for electrical transportation referred as windowed pulsewidth modulation (W-PWM). The windowed PWM (W-PWM) is derived by blending the principles of operation of conventional modulation schemes for MMC based on the nearest level control (NLC) and on PWM with the aim of combining their inherent strengths and offering a higher degree of flexibility. This can reduce switching losses compared to classical PWM schemes and lower the current harmonic distortion compared to NLC schemes. The window in which the PWM is applied can be seen as an additional degree of freedom that allows a dynamic optimization of the performance of the traction drive depending on its operating characteristics. The performance of the W-PWM technique is assessed in this article for several operating conditions and compared with conventional schemes based on NLC and on the phase opposition disposition PWM with both numerical simulation and experimental verification on a small-scale prototype. Results demonstrate the flexibility of the W-PWM and its potential for applications in electrical traction drives. © 1986-2012 IEEE.

The modular multilevel converter (MMC) for electric vehicle applications has been studied in recent years, for its advantages such as high modularity, fault tolerant ability and capability of multi-function (motor drive, cell equalizer and on-board charger) integration. However, during the operation of MMC, specific ac harmonics will be introduced in battery cell currents, reducing battery lifetime. A multiple common-mode voltages injection control method, increasing the frequency of the 2nd order current harmonic and allowing the filtering through smaller filters, is proposed in this paper, to mitigate the negative influence of current harmonics on battery lifetime. To eliminate the effect of injected common-mode components on the ac side, a hybrid MMC topology is also proposed. Simulation results verify the validity of the proposed method and topology.

The importance of monitoring voltage harmonics in distribution grids has raised because of the increasing diffusion of power electronics-based nonlinear devices. In this respect, the role of voltage transformers (VTs) is vital since they represent the input stage in power quality monitoring systems, and they are responsible for one of the major uncertainty contributions. Nevertheless, their metrological performances are still quantified in terms of accuracy class, namely, rating maximum ratio error and phase displacement. The aim of this article is moving from the concept of maximum error to that of uncertainty, while proposing a new approach to evaluate and express the accuracy of VTs employed for harmonic measurements. The method is applied to the calibration of a conventional inductive VT by means of a proper setup that allows injecting complex multitone waveforms. Experimental results clearly show the advantages of the proposed approach, which permits a better description of the metrological behavior with respect to the usual ratio error and phase displacement.

Harmonic distortions are going to be more important in the near future due to the growing utilization of power electronic (PE) based devices. The PE devices usually exhibit a nonlinear behavior leading to inject harmonics to the network. Meanwhile, widespread employment of distributed energy resources (DER) with their PE-based power conditioning units, may impose some harmonics into the network. Hence proper mitigation methods should be employed by distribution operators to enhance the level of the power quality. In this paper, a harmonic monitoring center (HMC) is proposed for central management harmonic mitigation activities of distributed harmonic active power filters (APFs). The compensation actions of APFs are determined by the HMC based on an optimization model called as APF commitment model. Economic satisfaction of harmonic standards is considered as the goal of optimization algorithm with respects to various technical and systematic constraints. In the simulations, the developed model shows a better performance and capability compared to the existing local management methods of distributed APFs.

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.

A simple and computationally efficient method to represent the geometry of hand-made random wire bundles is described, which can be exploited within a multiconductor-transmission-line model for prediction of the currents induced in bundle terminal units by an external electromagnetic field. As an illustrative example, a random bundle running above a metallic ground and illuminated by a uniform plane wave is considered. By processing the data resulting from repeated simulations (Monte Carlo approach), some significant properties of the statistics of the induced currents are observed. Particularly, it is shown that in the so-called “well randomized” bundles the probability density function of the magnitude of the induced currents tends to be Normal at low frequency and Rayleigh at high frequency.

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 this paper, the concepts of weak coupling and weak imbalance are exploited to investigate crosstalk and mode conversion occurring in perfectly balanced differential lines (DLs) due to proximity with other DLs printed on the same PCB substrate. Approximate modal circuits are derived, where the aforementioned phenomena are accounted for by the use of distributed voltage and current sources. This allows evidencing the relevant parameters at the basis of these undesired phenomena, which may significantly degrade DL performance in terms of emission and immunity properties as well as signal integrity. Accuracy of the proposed model, preliminary validated versus exact solution of transmission line equations, is eventually assessed through vector network analyzer measurements carried out on a PCB sample.

Voltage transformers are vital components for the operation of power systems. Because of the increasing diffusion of power electronics, nonlinear devices in distribution grids, their role is becoming even more important, since they represent the input stage in power quality monitoring instruments. Nevertheless, their metrological performances are still expressed in terms of accuracy class, namely rating maximum ratio and phase errors at fundamental and harmonic frequencies. The aim of this work is providing a contribution that allows migrating from the concept of maximum error to that of uncertainty. Calibration of an inductive voltage transformer has been considered as a case study and simulated through detailed modeling; this allows neglecting the impact of noise and that of the reference transducer. The statistical features of the measurement error are evaluated, and a method to quantify and express uncertainty is proposed.

Monitoring voltage harmonics represents one of the most important tasks in power quality assessment. In particular, the employed instrument transformer plays a key role in the achieved accuracy. Its harmonic measurement performance is typically evaluated by measuring its frequency response function. However, nonlinearities may have a nonnegligible impact on measurement uncertainty; for example, this occurs as far as the inductive voltage transformers are considered. This paper proposes a simple technique allowing the compensation of the most significant nonlinear effect that is the harmonic distortion produced by the large fundamental primary voltage. The method is first derived and introduced by means of numerical simulations and then implemented through a proper experimental setup. Results highlight remarkable accuracy improvements when realistic voltage waveforms are measured.

BroadR-Reach® is a point-to-point Ethernet Physical Layer standard for automotive applications, allowing full-duplex communication between two devices over an unshielded twisted-wire pair (UTP) at 100 Mb/s. The high transmission speed in combination with the use of an unshielded harness makes compliance of the BroadR-Reach® Ethernet with automotive Electromagnetic Compatibility requirements a challenging task. This paper investigates the main factors influencing the outcome of Bulk Current Injection (BCI) tests carried out on BroadR-Reach® Ethernet channels. To this end, experimental measurements, circuit and electromagnetic simulation of a simplified test setup are exploited. The analysis allows putting in evidence the fundamental role played by line length, injection probe positioning, and imbalance affecting the terminal units, as well as the impedance discontinuities introduced when the UTP has to be interfaced with a shielded (untwisted) wire-pair (SWP) of the fiber optics converter electronics.

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.

A multiconductor-transmission-line (MTL) model of field coupling to a random bundle composed of twisted-wire pairs (TWPs) running above ground is proposed for the computation of the induced common-mode (CM) noise. The nonuniform bundle is effectively represented by cascading uniform MTL sections, whose models are derived from a single reference solution through permutations of rows and columns in matrices and vectors. This is achieved by exploiting the concepts of: 1) averaged per-unit-length parameters, 2) reference cross-section, 3) minimum-distance shifts of TWP positions in the reference cross-section. Repeated-run analysis is used to outline the high sensitivity (tens of dBs) of the induced CM noise to random configurations of electrically long bundles, and to derive statistical estimates of CM voltages induced by a plane-wave field at each TWP terminal. Accuracy and computational efficiency of the proposed approach are proved by comparison versus full-wave simulations.

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.

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.

Measurement of voltage harmonics has become a crucial task in power quality assessment for several years. The achieved accuracy strictly depends on the employed transducer, which in many cases is represented by a conventional inductive voltage transformer. It is well known that such transducers suffer from an uneven frequency response that undermines their harmonic measurement performance; for this reason, compensation techniques based on a linear modeling have been proposed in the literature. However, the accuracy of inductive voltage transformers at low-order harmonics is severely jeopardized by nonlinear effects and in particular by the harmonic distortion due to the strong fundamental component typical of voltage waveforms in ac power systems. For the first time, this paper proposes a simple technique able to compensate also this nonlinear phenomenon, thus achieving a significant improvement in overall accuracy. The performance of the method is assessed by means of numerical simulations and the achieved results are extensively discussed.

Resorting to point-to-point communication between two devices over an unshielded twisted-wire pair (UTP), the BroadR-Reach® Physical Layer has the potential to assure very high transmission speeds. However, ensuring immunity of such high-speed data lines in the harsh electromagnetic environment of modern car architectures is a challenging task, requiring repeatable and reliable test procedures for immunity assessment. This work investigates and compares the performance of the Bulk Current Injection (BCi) and of the Tubular Wave Coupler (TWC) techniques-currently foreseen by the ISO standard up to 400 MHz and from 400 MHz up to 3 GHz, respectively-in testing the immunity of an UTP. The focus is on the sensitivity of the test outcome to poor positioning of the injection device on the cable harness. Indeed, preliminary measurement on canonical wiring structures revealed a more pronounced sensitivity to possible misalignment in the case of TWC rather than BCI setups, which is here investigated by means of a specific set of full-wave numerical simulations and interpreted by the light of simplified circuit models.

Pulsed current injection (PCI) allows testing the immunity of electric/electronics devices against fast and intense transient electromagnetic disturbances. This technique resorts to inductive couplers to directly inject noise currents into the harness entering the device under test (DUT). Although the characteristics of the stress waveform to be induced at the DUT input are assigned by the Standards, and set by calibration, the noise actually entering the DUT input ports may exhibit significant differences due to the frequency response of the injection device itself as well as specific setup arrangements. To investigate these influence factors, possibly compromising test significance, in this work a PCI test setup involving a wire-pair is setup and modeled in the SPICE environment. Measurements and simulations are exploited to put in evidence the effects that the presence of other wires (and their terminations) in the bundle play on the voltage waveform induced at the terminations of a specific wire. The results here presents are significant also in view of extending the analysis to more complex wiring configurations (currently ongoing), and in order to correlate the PCI technique with radiative immunity procedures foreseen by the Standards.

Measurements of synchronized phasors, frequency and rate of change of frequency from different locations on a wide area are the outputs of phasor measurement units (PMUs), which enable a frequent and accurate monitoring of power systems. PMUs have been conceived for monitoring ac transmission systems; in this case, they process the measurement signal provided by transducers that may have a strong impact on the overall performance. Capacitor voltage transformer represents one of the most widely employed transducer in high-voltage applications. In this paper, its effects on the response to amplitude and phase step signals of different, well-known PMU algorithms are investigated through numerical simulations. The paper proves that standard PMU characterizations or compliance verifications are not capable to identify the overall dynamic behavior of the device when installed on the field. Therefore, considering the effect of the transducer is a mandatory step towards the definition of measurement specifications for actual applications.

An array of weakly coupled oscillators can generate multiphase signals, i.e., multiple sinusoidal signals with specific phase separations. Multiphase oscillators are attractive solutions in many electronic applications such as the synchronization of multiple processing units in digital electronics and the frequency synthesis in mixed-signal radio frequency circuits. Due to the complexity of multiphase oscillators and the large number of design parameters, novel simulation techniques are highly desired to efficiently handle such large-scale problems. In this paper, an efficient phase-domain simulation technique is proposed to calculate the phase response of inductance capacitance oscillator array. By some practical examples, it is shown how the proposed method can be exploited to identify the array topologies and parameter settings that guarantee stable phase separations. It is also shown how the proposed technique can be used to evaluate phase-noise performance., National Science Foundation (U.S.). Nano-Engineered Electronic Device Simulation Node Program

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.

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.

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.

In this paper, the results of an experimental analysis performed on a polymer electrolyte membrane fuel cell (FC) for the evaluation of the current ripple effects are reported. The polarization curve (PC) and the impedance spectrum measured for a single FC with a Nafion membrane are presented discussing some advantages and disadvantages of the two adopted techniques from the measurement point of view. The ohmic and activation resistance values provided by the PC are compared to the frequency limits of the equivalent resistance estimated by the spectroscopic analysis to evaluate the additional losses and the system efficiency reduction introduced by the current ripple. The presence of a voltage–current hysteretic behavior is discussed throughout the paper, and some comments on how such a relationship can impact on the identification of the indicated parameters are included.

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.