Driving-point Impedance Research Articles

Evaluation of Medium Voltage Network for Propagation of Supraharmonics Resonance

Power converters with high switching frequency used to integrate renewable power sources to medium and low voltage networks are sources of emission in the supraharmonic range (2 to 150 kHz). When such converters are connected to a medium voltage (MV) network these supraharmonics propagate through the MV network and can impact network and customer equipment over a wide range. This paper evaluates an existing Swedish MV electrical network and studies the pattern of supraharmonic resonance and the propagation of supraharmonics. The MV network consists of eight feeders including a small wind farm. Simulations reveal that, the bigger the MV network, the more resonant frequencies, but also the lower the amplitude of the resonance peaks in the driving point impedance. It was also identified that for short feeders as length increases, the magnitude of the transfer impedance at supraharmonic frequency decreases. For further increment in feeder length, the magnitude increases or becomes almost constant. For very long feeders, the transfer impedance further starts decreasing. The eight feeders in the network under study are similar but show completely different impedance versus frequency characteristics. Measurements at the MV side of the wind farm show time varying emissions in the supraharmonic range during low power production. The impact of these emissions coupled with system resonance is examined.

Measurement Technique for Air Capacitance Standards for the Accurate Measurement of Electrical Components using Impedance Analyzers

A measurement technique for a commercial four-terminal (4 T) air-dielectric capacitance standard set (Keysight 16380A) for frequencies from 1 kHz up to 13 MHz was developed for the accurate calibration of impedance analyzers. The technique consists of a measurement of capacitance at 1 kHz using a precision bridge, seven measurements of one-port driving point impedance (DPI) over 30 MHz using a vector network analyzer (VNA), and various numerical calculation procedures for parasitic component estimation and uncertainty propagation. The contribution from parasitic components in the frequency range of interest (FRI) from 1 to 13 MHz was estimated by extrapolation from the measured impedance using a VNA. A linear model for parasitic components was employed to extrapolate DPIs for a reliable estimation. The uncertainty of the calibration was estimated using Monte-Carlo (MC) simulation. The developed technique demonstrated better efficacy than others for the calibration of 100 pF and 1000 pF standards in FRI by applying simple, but reliable linear extrapolation models and Monte-Carlo (MC) simulation for uncertainty evaluation.

Understanding the Origin of SSR in Series-Compensated DFIG-Based Wind Farms: Analysis Techniques and Tuning

This paper is dedicated to presenting control-tuning methodologies for the rotor-side converter (RSC) and grid-side converter (GSC) of series-compensated DFIG-based wind farms (WF) and to determining the origin of subsynchronous resonance (SSR). Unlike conventional approaches to re-tuning controller gains to achieve desirable performance, these methodologies only consider the mathematical models of the states variables to be controlled. A PI cascade topology is used to control the RSC and GSC. An inner loop is required for current control and an outer loop for voltage control. Special consideration is taken for tuning the RSC because this converter is coupled with the mechanical variables as mechanical rotor speed of the DFIG. Compared with standard tuning, a better system behavior during a resonance condition is achieved with the proposed tuning methodology. Regarding the analysis of the SSR origin, the modal impedance (MI) technique is used as a tool to study SSR issues; its advantages compared to the driving point impedance technique are highlighted. In this context, the small-signal-stability (SSS) analysis is performed to evaluate the overall system. With the combination of MI and SSS, the phenomena of induction generator effect, torque interaction, and torque amplification are analyzed. As a result, the modes involved in the SSR phenomenon are identified and a discrimination procedure is described to determine the origin of the SSR.

Fractional-Order and Power-Law Shelving Filters: Analysis and Design Examples

Low-pass and high-pass non-integer shelving filter designs, which are suitable for acoustic applications, are presented in this work. A first design is based on a standard fractional-order bilinear transfer function, while a second one is based on the transposition of the integer-order transfer function into its power-law counterpart. Both transfer functions are approximated using the Oustaloup approximation tool, while the implementation in the case of the power-law filters is performed through the employment of the concept of driving-point impedance synthesis. An attractive benefit is the extra degree of freedom, resulting from the variable order of both fractional-order and power-law filters, which allows improved design flexibility compared to the case of integer-order filters. From the implementation point of view, only one building block is required to realize both filter types, thanks to the employment of the Voltage Conveyor.

A Millimeter-Wave Receiver Using a Wideband Low-Noise Amplifier With One-Port Coupled Resonator Loads

This article presents design techniques to facilitate the use of the driving point impedance (Z 11 ) of one-port transformer-coupled resonators as wideband loads of millimeter-wave amplifier stages for a 28-GHz receiver front end. While the use of both the Z 11 of a one-port and the transimpedance (Z 21 ) of a two-port coupled resonator is considered to achieve a wideband response, it is shown that under conditions of low magnetic coupling and constrained network quality factor, the use of Z 11 can result in a higher gain-bandwidth product of low-noise amplifier (LNA) amplifier stages. The effect of the complex zero in the Z 11 response on the in-band gain ripple is shown to be alleviated merely by lowering the quality factor of the transformer's secondary coil; this strongly motivates the use of compact, nested-inductor transformer layouts. Implemented in a 65-nm CMOS process, a three-stage LNA (with Z 11 wideband loads in two stages) achieves a 24.4-32.3-GHz bandwidth (27.9 % fractional bandwidth), a peak S 21 of 24.4 dB (20.4 dB), a minimum noise figure (NF) of 4 dB (4.6 dB), and an input-referred P1dB of -23 dBm (-22 dBm) while consuming 22-mW (9.9 mW) power from a 1.1-V (0.85 V) supply. The use of compact transformers limits the LNA's footprint to only 0.12 mm2. A 26.5-32.5-GHz quadrature receiver prototype employing the LNA achieves a 29.5-dB peak conversion gain, a 5.3-dB minimum NF, and a -26-dBm inputreferred P1dB while consuming 33 mW from a 1.1-V supply.

Synthesis and Design of Enhanced N-Path Filters With 60-dB/decade RF Selectivity

A “third-order” passive mixer-first receiver is presented to improve channel selectivity and resilience to close-in blockers, by building an N-path filter which drives an impedance with 60-dB/decade roll-off. A step-by-step derivation is provided for the synthesis of the first ever driving point impedance with 60-dB/decade roll-off. An integrated circuit prototype was fabricated in 28-nm bulk CMOS as proof-of-concept and characterized. The receiver front-end is capable of broadband operation from 0.2 to 4.5 GHz, demonstrates third-order filtering of close-in blockers, and achieves an out-of-band IIP3 of +21 dBm and B1dB of greater than 6 dBm for blockers at the alternate channel. Additionally, it achieves a noise figure of 6.8 dB in the presence of a 0-dBm blocker.

Comments on “Decoupling Capacitor Placement on Resonant Parallel-Plates Via Driving Point Impedance” [Jun 19 2162-2171

In [1] , a semianalytical method based on 2-D Newton-Raphson algorithm is proposed to evaluate the effectiveness of decoupling capacitor placement on a rectangular power plane. Lei et al. [2] present analytical derivation of the Jacobian matrix elements and the related partial derivative expressions based on the cavity mode expansion of power-ground plane impedance. Unfortunately, some of the presented Jacobian matrix element expressions presented in [1] does not correspond to the proposed second relation for the application of the Newton-Raphson algorithm. Also, several errors are found in the presented results regarding the power-ground plane impedance, and various partial derivative expressions for the input impedance and the impedance of parallel plates in [1] . These errors are investigated and corrected in this work.

3D Smith charts scattering parameters frequency-dependent orientation analysis and complex-scalar multi-parameter characterization applied to Peano reconfigurable vanadium dioxide inductors

Recently, the field of Metal-Insulator-Transition (MIT) materials has emerged as an unconventional solution for novel energy efficient electronic functions, such as steep slope subthermionic switches, neuromorphic hardware, reconfigurable radiofrequency functions, new types of sensors, terahertz and optoelectronic devices. Employing radiofrequency (RF) electronic circuits with a MIT material like vanadium Dioxide, VO2, requires appropriate characterization tools and fabrication processes. In this work, we develop and use 3D Smith charts for devices and circuits having complex frequency dependences, like the ones resulting using MIT materials. The novel foundation of a 3D Smith chart involves here the geometrical fundamental notions of oriented curvature and variable homothety in order to clarify first theoretical inconsistencies in Foster and Non Foster circuits, where the driving point impedances exhibit mixed clockwise and counter-clockwise frequency dependent (oriented) paths on the Smith chart as frequency increases. We show here the unique visualization capability of a 3D Smith chart, which allows to quantify orientation over variable frequency. The new 3D Smith chart is applied as a joint complex-scalar 3D multi-parameter modelling and characterization environment for reconfigurable RF design exploiting Metal-Insulator-Transition (MIT) materials. We report fabricated inductors with record quality factors using VO2 phase transition to program multiple tuning states, operating in the range 4 GHz to 10 GHz.

A Robust Impedance Controller Design for Series Elastic Actuators using the Singular Perturbation Theory.

Impedance control is capable of further flexibly adjusting the driving-point impedance of series elastic actuators (SEAs) in addition to impedance reduction by the elastic element. This enhances safety and compliance during interaction between humans and robots, in comparison with rigid robots under impedance control or SEAs under position control. In this study, we propose an impedance controller for SEA systems that is developed based on the singular perturbation (SP) theory and time-delay estimation (TDE) technique. The SP theory allows for alleviating the burden of the requirement for states to be measured. The TDE technique is effective in compensating for system dynamics and uncertainties involved in system behaviors with minute computation loads. Employing both a simulation study and experimental study, we demonstrate the efficacy of the proposed control created from the combination of the SP theory and TDE technique. The effect of the proposed impedance control on reducing the driving-point impedance of interacting SEAs is examined.

Shape memory alloy actuation of non-bonded piezo sensor configuration for bone diagnosis and impedance based analysis.

In the recent years, there has been a growing interest in research community towards the application of smart materials for bio-medical structural health monitoring. Amongst the smart materials, directly bonded piezo sensors (DBPS), based on the electro-mechanical impedance (EMI) technique, have been successfully employed for the above purpose. The principle behind the EMI technique is that high frequency excitations (typically > 30kHz) generated by a surface bonded PZT patch are used to detect changes in structural drive point impedance caused by cracks or any other type of damage. Bone healing and damage have been shown to be successfully monitored using the DBPS. However, in most of the diagnostic cases of live human and animal subjects, directly bonding a PZT patch is always an irritant or hazard for a live subject. To circumvent direct bonding, the authors have developed and experimentally demonstrated a non-bonded piezo sensor (NBPS) configuration as a good alternative to DBPS while maintaining the effectiveness of measurement well within discernible limits. This paper presents further improvement in the NBPS configuration aiming at autonomous operation of the gripping mechanism using shape memory alloy (SMA) wires. The experiments are performed on replicas of femur bone in healthy and osteoporosis state. This paper shows the effective use of SMA clamping for bone identification and its damage assessment in comparison to earlier mechanical gripping using jubilee clamps. This paper also covers impedance based identification applied to SMA and clamp based NBPS configurations. In place of raw admittance signatures, effective drive point impedance is utilized for the purpose of bone diagnostics which provides a more realistic assessment of the condition of bone.

Analytical Expressions to Link SCNF and OCNF of Transformer Windings to Their Inductances and Capacitances for 1-$\Phi$, 3-$\Phi$ Y and $\Delta$ Configurations

Recently, the present authors’ research group derived an analytical expression to link the harmonic sum of the squares of short circuit natural frequencies (SCNFs) of a single, isolated winding to its elementary inductances and capacitances. Also, it was demonstrated how this expression could be practically used for locating radial and axial displacements, along with assessing its severity on a single, isolated, actual transformer winding. The next logical task was to extend the derived expression to multi-phase windings, viz., star/delta connections and for any terminal condition of the neutral. Actually, it would be desirable to have a similar expression for open circuit natural frequency (OCNF) as well. A major highlight of this paper is that it presents a single, unified approach (using salient features of coefficients of the numerator and denominator polynomial of driving-point impedance) by which compact analytical expressions can be simultaneously derived for both SCNF and OCNF, for any multi-phase transformer configuration, and for any condition of the neutral terminal. Complete derivation details of the proposed method are presented, and then, the expressions for SCNF and OCNF are derived for 1- $\Phi$ isolated windings as well as 3- $\Phi$ (Y, $\Delta$ ) configurations. Finally, simulation results for all the cases are reported.

Design and Analysis of an Origami-structured Actuator for Backdriveability and Power Amplification

An origami-structured compliant actuator (OSCA) is developed for human–robot interaction, in which adequate power output, as well as safety, is emphasized under a limited power supply. The OSCA inherits the safety feature from soft actuators, while, at the same time, it ensures that expansion in off-axis directions is converted to on-axis moment. The kinematic singularity originating from its actuator design gives rise to a significant mechanical advantage over certain ranges of motion. The compressibility of airflow within the actuator essentially provides both backdriveability and elasticity, the latter contributing to increasing the actuator's power output in the same way as does a series elastic actuator. In this study, the design of an actuator structured based on origami is presented, and analyses on benefits in moment amplification and power amplification from the OSCA design and air compressibility are examined. These efforts provide an insight into producing high power by the OSCA in unison with a low driving-point impedance.

Investigations into the acoustics of the mandolin

The mandolin is a descendent of the lute with a long history starting in 18th century Italy. This talk will give a brief history of the mandolin culminating in the modern flat-back mandolins used in bluegrass music. After a summary of previous research into its acoustics, we will describe our current research. This includes the use of Electronic Speckle Pattern Interferomentry (ESPI) to study the low-modes of the front and back plates and studies of the driving point impedance at the bridge. The mandolin has four courses of doubled strings tuned in unison. Inspired by Weinreich’s seminal study of piano strings, we explore the coupling of the strings’ motions to each other through their attachment to the vibrating bridge. By using a macro lens on a high-speed camera, we are able to study these motions in exquisite detail. We observe clear evidence of coupling including the exchange of energy between the vertical and horizontal motions of each string and correlations in the phases of their motions. We interpret the experimental results in the context of a theoretical model. [Work supported by the National Science Foundation under Grant No. 1707978.]

On boundary analysis for derivative of driving point impedance functions and its circuit applications

In this study, a boundary analysis is carried out for the derivative of driving point impedance (DPI) functions, which is mainly used for the synthesis of networks containing resistor-inductor, resistor–capacitor and resistor–inductor–capacitor circuits. It is known that DPI function, Z ( s ) , is an analytic function defined on the right half of the s-plane. In this study, the authors present four theorems using the modulus of the derivative of DPI function, | Z ′ ( 0 ) | , by assuming the Z ( s ) function is also analytic at the boundary point s = 0 on the imaginary axis and finally, the sharpness of the inequalities obtained in the presented theorems are proved. It is also shown that simple inductor–capacitor tank circuits and higher-order filters are synthesised using the unique DPI functions obtained in each theorem.

Boundary Analysis for the Derivative of Driving Point Impedance Functions

Four theorems are presented in this brief by performing boundary analysis of the derivative of driving point impedance functions evaluated at the origin. Also, the circuits corresponding to these driving point impedance functions, which are obtained as the natural results of presented theorems, are given. Driving point impedance functions are mainly used for synthesis of networks containing RL, RC, and RLC circuits. Considering that the driving point impedance function, ${Z(s)}$ , is an analytic function defined on the right half of the s- plane, we derive inequalities for the modulus of the derivative of driving point impedance function, ${|}{Z}^{\prime } {(0)|}$ , by assuming the ${Z(s)}$ function is also analytic at the boundary point ${s=}{0}$ on the imaginary axis with ${Z(0)=}{0}$ . Finally, the sharpness of these inequalities are proved. Unique driving point impedance functions are obtained as intuitive results of presented theorems in the study and it is also shown that the extremal functions correspond to the driving-point impedances of simple LC circuits.

Dynamic Matching System for Radio-Frequency Plasma Generation

Plasma generation systems represent a particularly challenging load for radio-frequency power amplifiers owing to the combination of high operating frequency (e.g., 13.56 MHz) and highly variable load parameters. We introduce a dynamic matching system for inductively coupled plasma (ICP) generation that losslessly maintains near-constant driving point impedance (for low reflected power) across the entire plasma operating range. This new system utilizes a resistance compression network (RCN), an impedance transformation stage, and a specially configured set of plasma drive coils to achieve rapid adjustment to plasma load variations. As compared to conventional matching techniques for plasma systems, the proposed approach has the benefit of relatively low cost and fast response, and does not require any moving components. We describe suitable coil geometries for the proposed system, and treat the design of the RCN and matching stages, including design options and tradeoffs. A prototype system is implemented and its operation is demonstrated with low pressure ICP discharges with O $_{2}$ , C $_{4}$ F $_{8}$ , and SF $_{{6}}$ gases at 13.56 MHz and over the entire plasma operating range of up to 250 W.

Efficient Decoupling Capacitor Placement Based on Driving Point Impedance

With rapidly increasing switching speeds and surge current requirements, placement of local decoupling capacitors is becoming critically important in high-speed low-power designs. In this paper, utilizing the driving-point impedance (viewed from the device pin) as a metric, a new method is presented for the placement of decoupling capacitors in parallel-plate power ground pairs of high-speed circuits. In the proposed approach, instead of using the traditional trial-and-error method to identify an appropriate placement distance, the process is formulated in the form of a transcendental function. The resulting function is solved using Newton–Raphson (N-R) iterations to give a direct solution for the distance. Also, an analytical representation based on Hankel functions for the driving point impedance and its derivatives is developed to speed up the N-R iterations. The proposed method is validated by comparing the results with the full-wave electromagnetic simulations.

Design of High Efficiency Broadband Continuous Class-F Power Amplifier Using Real Frequency Technique With Finite Transmission Zero

In this paper, a new methodology using a distributed ladder structure with finite transmission zero at finite frequencies is proposed for designing a broadband high-efficiency continuous Class-F (CCF) power amplifier (PA). The approach of realizing finite transmission zeros in Richard domain using Real Frequency Technique is first presented. By applying the proposed approach, the characteristics of the driving point impedance (DPI) of the proposed structure can be deduced and obtained in theory. Furthermore, the synthesis methods in Richard domain are extended to synthesize the DPI of the proposed structure. Four types of distributed elements are investigated to synthesize the DPI of the proposed structure. This proposed structure can improve the performance of the CCF PA when the bandwidth approaches an octave as the finite transmission zero can be used to control the second harmonic impedance of the lower frequency which is near the upper frequency of the operation band. To verify the validity of the proposed method, a broadband high-efficiency CCF PA working from 1.15 to 2.2 GHz is designed. Experimental results show that the fabricated PA achieves 11.3–13.7 dB power gain and 40.5–43.2 dBm output power in the operation band. And the PA has also achieved a high-efficiency characteristic of 70%–83% drain efficiency (DE) over the whole operation bandwidth.

Identification of Modeling Boundaries for SSR Studies in Series Compensated Power Networks

Given large-scale power networks with series compensation, the study of subsynchronous resonance (SSR) is a significant challenge, in practice, due to the model complexity and computation burden. To tackle these difficulties, this paper proposes a method to reduce a large-scale system to an equivalent model using a metric called damping sensitivity index. The proposed metric can quantitatively identify the boundaries of the equivalent model that ensure the accurate studies of SSR and reduce the computation burdens greatly. The effectiveness of the method is verified by its application to the SSR investigation of the modified IEEE New England 10-machine 39-bus system and 16-machine 68-bus system. The equivalent models obtained by the proposed method are compared with the original systems in terms of driving point impedances, electrical damping, and transient torques. These results obtained show that the equivalent models from the proposed method can reproduce the SSR dynamics of the original systems with a much shorter computation time.

Measurement-based electrical parameters of power transformers for Frequency Response Analysis interpretation-Part II: Winding Part II: Winding analysis

For a practical Frequency Response Analysis (FRA) interpretation applicable to power transformers, frequency dependent electrical parameters of the core and windings in broad frequency range should be identified through non-destructive measurements. Since the core parameters are determined in Part I, electrical parameters of windings (resistances, capacitances) and leakage paths surrounding windings (leakage/zero-sequence impedances) of a distribution transformer will be discussed in this paper. Due to the fact that most parameters associated with the windings currently can only be measured at or around power frequency through diagnostic testing methods, the practical parameter-based FRA interpretation is not possible. To deal with this problem, the paper proposes a new approach based on the combination of different measured driving-point impedances and relevant analysis of the duality-based equivalent circuit in determining frequency dependent parameters associated with transformer windings. Results show that the physical FRA interpretation can be reasonable obtained for the test transformer in low and medium frequency range.