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Phasor measurement units (PMUs) are the measurement devices fostering the transformation of electric power networks towards the smart grid paradigm. They should accurately measure synchrophasors, frequency, and rate of change of frequency (ROCOF), so that the management and control applications relying on PMU-based distributed monitoring systems can operate effectively. Commercial PMUs performance is typically guaranteed by the compliance with the IEEE standard C37.118.1, which is focused on PMUs for power transmission systems and defines testing conditions and error limits. However, actual operating conditions are much more variable than those covered by the standard, especially when PMUs are used in distribution networks. In particular, the standard does not consider unbalance, which may be negligible neither in transmission nor in distribution grids. For the first time, this paper analyzes the impact of unbalance on the accuracy of four of the most significant classes of signal processing algorithms for PMU measurements. Synchrophasor, frequency, and ROCOF estimation performances under different unbalance conditions are investigated in the test cases suggested by the IEEE C37.242-2013 guide. Novel analytic expressions to predict the errors are derived and validated, and they are proved to be useful for an effective implementation of PMU algorithms intended for both distribution and transmission systems.

This paper developed a novel single-phase reactive current detection algorithm based on fast orthogonal signal generator (OSG) and enhanced moving average filter (MAF), overcoming the limitation of conventional schemes in detection speed, computation burden and noise/harmonic immunity. A fast and accurate OSG scheme is introduced first, which can remarkably improve the precision and response speed of the developed detection scheme. In d-q frame, the enhanced MAF is developed and its optimal design principle is also presented, which can sufficiently eliminate the noise and harmonics while achieve the possible shortest response time, particularly in the case of selective harmonics cancellation. Finally, high-performance single-phase STATCOM control is realized utilizing the proposed method. Experiments reveal that the proposed detection scheme exhibits fast speed, high precision as well as noise/harmonics immunity, providing satisfactory control performances.

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.

This paper describes the realization of a sensor capable of measuring the volume of a drop in free fall. The sensor realized is made of a simple low-cost red laser and a photodiode and optics to focus the beam on the light sensor. In this way, when the drop is falling down, it is possible to estimate its volume from the signal generated on the photodiode while getting through the laser beam. This system may be very useful together with a drip chamber to have accurate and low-cost volume and flow rate measurements of the infused substances.

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.

Conditional probability distributions and Bayes’ theorem are important and powerful tools in measurement, whenever an a priori knowledge about the measurand is available. It is well known that, thanks to Bayes’ theorem, a new information about the measurand coming from a measurement result can be used to revise the a priori knowledge refining its uncertainty. Of course, this tool can be used only if both the a priori knowledge and the new information are expressed in terms of probability distributions. However, according to a recent approach to uncertainty evaluation, measurement results can be also expressed using random-fuzzy variables (RFVs), that is, using possibility distributions, instead of probability distributions. This paper proposes an extension of Bayes’ theorem to the possibility domain, thus leading to the definition of conditional RFVs. A simple experimental example is also considered to prove the effectiveness of the proposed extension.

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.

We apply balanced detection to self-mixing interferometry for displacement and vibration measurement, using two photodiodes for implementing a differential acquisition. The method is based on the phase opposition of the self-mixing signal measured between the two laser diode facet outputs. The balanced signal obtained by enlarging the self-mixing signal, also by canceling of the common-due noises mainly due to disturbances on laser supply and transimpedance amplifier. Experimental results demonstrate the signal-to-noise ratio significantly improves, with almost twice signals enhancement and more than half noise decreasing. This method allows for more robust, longer-distance measurement systems, especially using fringe-counting.

In this paper, a novel approach for statistical analysis of cable harnesses characterized by several random parameters is proposed, which is based on a perturbative reformulation of the well-known stochastic Galerkin method (SGM). With respect to the traditional SGM, the proposed method avoids the solution of an augmented multiconductor transmission line (MTL), whose dimensions may become prohibitive in case of structures characterized by several wires and random parameters. Namely, it resorts to the iterative and repeated solution of a MTL having the same number of wires as the original structure, where the effects of random variations of geometrical parameters are included by means of equivalent sources. The proposed approach is here applied to collect statistical information of voltages and currents at the terminations of a shielded cable. Through such an example, involving a large number of wires (7) and random variables (12), it is proven that the proposed method yields a significant reduction of computational time with respect to the traditional SGM, at the same time providing similar accuracy in the prediction of statistical moments.

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.

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.

This paper investigates the efficiency of a perturbative approach for the statistical assessment of differential transmission lines affected by random parameters. Within the polynomial chaos framework, the novel technique reformulates the so-called stochastic Galerkin method in a decoupled and iterative fashion. Instead of solving the classical, augmented and fully coupled transmission line equations, the new approach iteratively solves multiple uncoupled line equations with nominal per-unit-length parameters and suitable equivalent distributed sources accounting for their variability. The methodology is applied to a system of up to four PCB differential pairs. A computational advantage is observed against the classical stochastic Galerkin method for large problems in terms of number of random parameters and/or conductors.

This paper presents a novel approach for the statistical analysis of differential interconnects with random parameters. The proposed method employs a perturbation technique to reformulate the augmented multiconductor transmission line (MTL) equations generated by the polynomial chaos based stochastic Galerkin method. The augmented MTL-like equations are recast as the equation for a deterministic MTL with average per-unit-length parameters and additional equivalent distributed sources that account for their variability. The process leads to multiple MTL problems of the same size as the original one, which are solved iteratively in the frequency domain. Moreover, for each iteration, the solution of each MTL problem is independent. The feasibility of the proposed approach is illustrated through the statistical analysis of a canonical PCB differential line with random geometrical parameters. Computational advantages with respect to the classical stochastic Galerkin and Monte Carlo methods are discussed along with the effect of the amount of variability on the performance.

The widespread diffusion of nonlinear power electronics devices in power systems has radically changed their operating scenario. Voltage and currents can be significantly distorted, and conventional linear models of power system components may be not accurate enough. Simplified Volterra models with quasi-sinusoidal excitation have been recently proposed, and they are particularly suitable to represent the behavior of power systems devices. In this paper, the simplified Volterra approach is applied to the frequency-domain modeling of a typical highly-nonlinear load: a full-bridge rectifier feeding an ohmic-capacitive load. Model accuracy has been evaluated by means of numerical simulations, and its performance has been compared with that achieved by a conventional Volterra model. Results highlight the excellent accuracy of the proposed model in spite of the relatively small set of coefficients to be identified. This feature is extremely important when models have to be employed in frequency-domain simulations of large networks.

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.

We present an overview of the applications of self-mixing interferometer (SMI) to tasks of interest for mechanical engineering, namely high-resolution measurement of linear displacements, measurements of angles (tilt, yaw, and roll), measurements of subnanometer vibrations, and absolute distance, all on a remote target—representative of the tool-carrying turret of a tool-machine. Along with the advantages of SMI—compactness, low cost, minimum invasiveness, ease of use, and good accuracy, we illustrate the typical performance achieved by the basic SMI sensors, that is, the versions requiring a minimum of signal processing and discuss special features and problems of each approach.

This work presents the results of an experimental campaign aimed at validating a recently developed alternative radiated susceptibility (RS) procedure based on the use of bulk current injection (BCI). The rationale of such a procedure consists in the injection of common-mode (CM) conducted disturbances in a certain excess over RS, which is quantified by an engineering margin called overtesting (OT). From the standpoint of the test operator, owing to lack of knowledge about the frequency response of the CM impedance of terminal equipment, OT results to be a random variable. However, its statistics was shown to be predictable through theoretical analysis based on circuit modeling. Unlike previous works, where experimental validations relied on simple cables and basic terminal units, a realistic test setup mimicking typical aerospace harness and equipment is here exploited. An extensive test campaign was carried out to collect data sets for the estimation of the cumulative distribution function of OT. Results corroborate the validity of the proposed approach up to 1 GHz.

The paper describes capabilities of a topological model of three-phase, five-limb transformer to accurately represent its response when subjected to geomagnetically induced currents. The model is validated by close agreement of the predicted values and waveforms of the currents, voltages, and reactive power with those measured in tests performed on two 400 MVA transformers connected back-to-back and to the Fingrid power network. Results demonstrate the importance of incorporating the network representation and dispel some misconceptions about the influence of the hysteretic properties of the core and tank in modeling five-limb transformers.

This paper investigates the statistical effects of additive noise on the magnitude of the space-vector spectral lines estimated through a discrete Fourier transform (DFT). In fact, the space vector is a well-known and effective tool for monitoring power quality issues in modern power systems. In many practical cases waveform distortion requires a DFT in order to extract the fundamental component and the harmonic/interharmonic content. In particular, the space vector shape (on the complex plane) of the fundamental component provides information such as voltage dips, whereas space-vector spectral lines provide information related to waveform distortion. Additive noise mainly impacts on low-magnitude spectral lines which require a statistical characterization. Conventional results available in the literature cannot be used in a straightforward way because a space vector is a complex-valued function, therefore special care is needed for proper interpretation and use of its properties in the frequency domain. In the paper, the probability density function, the mean value and the variance of the magnitude of space-vector DFT spectral lines are derived in closed form. Analytical results are validated by means of numerical simulations.

The Volterra approach to the modeling of nonlinear systems has been employed for a long time thanks to its conceptual simplicity and flexibility. Its main drawback lies in the number of coefficients, which rapidly grows with memory length and nonlinearity order. In some important cases, such as power system applications, the input signal is periodic and contains a fundamental component that is much larger with respect to the others. This peculiarity can be exploited in order to dramatically reduce the number of coefficients defining the frequency-domain Volterra model with slight drawbacks in terms of accuracy. A systematic procedure for the definition of simplified, frequency-domain models of arbitrary order is proposed. Thanks to the simplification, very high orders of nonlinearity can be managed. The proposed approach has been employed to model the behavior of two electrical devices with different amount of nonlinearity, and that of a power grid containing linear and nonlinear loads. Accuracy is discussed and compared with that obtained with a conventional Volterra model defined by a similar number of coefficients. Results show the effectiveness of the approach, which is particularly suitable to model and test voltage and current transducers as well as other ac power system devices.

In this letter, a pulse current injection (PCI) setup involving a pulse generator with adjustable parameters is designed and modeled in SPICE. In order to allow causal and accurate time-domain simulation, the circuit model makes use of an augmented network to approximate the non-rational frequency response of the injection probe. The obtained SPICE model is preliminary validated by measurement for different sets of values of the pulse-generator parameters. Afterward, an explicative example of radiated test setup is considered. The stress waveform induced at the points of entry of the equipment under test by radiation (evaluated either by theoretical prediction or by measurement in a low-level radiation environment) is taken as reference to prove the effectiveness of the proposed PCI-setup model in identifying the values of the generator parameters required to reproduce the same disturbance by PCI.

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.

This letter investigates the coupling of a plane-wave field to a twisted-wire pair (TWP) running above ground, with the objective to handle the practical relevant case of dielectric coating surrounding the two wires in the TWP. Closed-form expressions of the equivalent modal sources accounting for field-to-wire coupling are derived, and used to predict the modal voltages/currents induced at the TWP terminations. To represent propagation of the induced interference along the twisted line, per unit length parameters numerically evaluated on the average TWP cross section are exploited. Full-wave numerical simulations carried out by the Method of Moments confirm the accuracy of the proposed prediction model.

This paper proposes a simplified optimum control strategy for a monoinverter dual parallel (MIDP) permanent magnet synchronous motor (PMSM). With reference to the parallel PMSM unified model, two different auxiliary conditions are investigated. The first minimizes the supplied inverter current, and the second maximizes the motor's efficiency. Their formal expressions are derived by the introduction of three new normalized variables, linked to the load conditions. Thus, the optimum tracking considerations are general, and the parameters are independent. Simplified closed analytical forms are found for the optimum tracking, independently under steady-state and transient conditions. The selection of the best solution is then found via a parameter independent look-up table, and imposed through a closed-loop control diagram. The proposed control is compared to the present state of the art via experiments on a 1400-W MIDP PMSM test bench, showing an equivalent performance, with a lower computational burden.

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.

Up to few years ago, one of the main problems in the optimal design of a battery energy storage system (BESS) was the availability of both the generation (e.g. renewable sources) and load power profiles of the considered plant. This paradigm has limited the potential of BESSs to drive down overall energy costs and reduce carbon emissions. Nowadays, the exponential growth of data available on the industrial plants has opened the way to new possibilities and opportunities. In addition, BESSs are a viable opportunity to start transforming existing plants with an incremental hybridization of the plant topology. In light of the above, this work develops a commissioning tool that, starting from the data collected on the field, provides the final users the optimal dimensioning of any BESS - according to the taraet performances required bv the specific application.

Nowadays, electric vehicles (EVs) are of great interest over the world. In the past, the diffusion of EVs was impeded because of the limits of energy storage units, which reflect in vehicle range limited extension. In recent years, a significant progress was made in terms of power and energy density thanks to the lithium based batteries that can guarantee vehicle ranges higher than 100 km. Another further step can be done by coupling more than one storage technology and leading to an increased efficiency and extension of the vehicle range. In this paper, the effectiveness of adding another storage unit to a lithium ion battery is investigated for different EVs and driving cycles. Furthermore, a methodology procedure, based on the knowledge of the test driving cycle, and parameters of the EV, is proposed to find the optimal size of the auxiliary storage, that maximizes the EV range.

In this paper, a SPICE model representative for the mode conversion occurring in differential lines affected by imbalance either of the line cross-section and the terminal networks is developed. The model is based on the assumption of weak imbalance and allows approximate prediction of modal quantities, through separate modeling of the contributions due to line and termination imbalance by controlled sources with (possibly) frequency dependent gain. The proposed SPICE model is used to perform worst-case prediction of undesired modal voltages induced at line terminals by mode conversion.

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.

This paper deals with the transformation from differential to common mode noise due to slightly unbalanced filter capacitors in a three-phase motor drive system. Indeed, filter components, i.e., inductors and capacitors, can be slightly different due to the tolerance of commercial products usually varying from 5% to 20%. Such components discrepancies result in noise transformation from differential to common mode. This phenomenon is clearly evident in experimental setups where differential mode resonances can be observed in the common-mode current. In this paper, noise transformation is described in terms of an approximate equivalent circuit based on the symmetrical components transformation. The equivalent circuit derived in the paper allows straightforward analytical evaluation of the contribution to the common-mode current ascribed to the discrepancies of the filter capacitances with respect to the nominal symmetrical value.

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.

Three-dimensional imaging solutions provide depth perception that cannot be achieved with traditional two-dimensional systems. A 3D optical inspection system can be implemented using structured light as 3D sensing technology. In this paper, we show that structured light can be projected onto the measured object by means of an innovative scanning microsystem that employs a single-axis torsional MEMS mirror for fast steering a near infra-red laser beam on a diffractive silicon microstructure. As a proof of principle of the functionality of the designed microsystem, the generated line patterns are shone on 3D objects and deformation of the projected lines is detected with a CMOS camera. From line deformation, the object depth is calculated and found in accordance to the geometrical size. The developed miniaturized solution overcomes typical drawbacks of other scanning technologies such as large size and heavy weight.

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.

The interest towards nonlinear system modeling and identification is growing in the last years since more and more often the usual linear time invariant approach is not able to satisfy the requirements in terms of accuracy. Among the several types of nonlinear models, the Volterra series represents a very effective tool, being the straightforward generalization of the conventional approach. However, the number of coefficients grows exponentially with the order of nonlinearity to be considered. Therefore, in common applications, only low-order Volterra models are employed. Nowadays, the increase of computational power makes possible to employ frequency-domain Volterra models having a nonlinearity order higher than two or three, but a procedure allowing to write the frequency-domain kernels in a simple way has not been developed yet. The purpose of this work is to present an iterative method that allows writing the generic expression of frequency domain Volterra models considering a generic number of input harmonics and order of nonlinearity.

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.

This paper proposes a novel framework for the signal integrity (SI) analysis of differential interconnects affected by nonuniformity and geometrical asymmetry. The pertinent nonuniform transmission-line (TL) equations are solved in the frequency domain by means of a perturbation technique, which allows interpreting the resulting response degradation as a perturbation with respect to the response of a reference uniform differential line (DL) with averaged per-unit-length (p.u.l.) parameters. Following this interpretation, the problem is recast as a standard TL equation for the reference uniform line with additional equivalent distributed sources that account for the perturbative effect of asymmetric nonuniformity. This equivalent perturbation problem is solved iteratively in the frequency domain, and the corresponding time-domain behavior is obtained via inverse Fourier transform. Moreover, upon consideration that local perturbations negligibly impact on far-end differential mode (DM) quantities, the uniform DL model with averaged p.u.l. parameters is used for the SI performance evaluation of transmitted DM voltages in SPICE, showing that comparable results can be obtained while avoiding the cumbersome implementation of a nonuniform transmission line topology. The methodology is applied to the prediction of the eye diagram degradation for a 20 Gbps transmission through a microstrip DL subject to geometrical asymmetry and nonuniformity.