Active Impedance Research Articles

Embedded active impedance source inverter: Analysis and implementation

AbstractIn this paper, a new active impedance source inverter with a suitable control method based on the pulse‐width modulation (PWM) technique is proposed. Based on the proposed control method, the analysis of the proposed inverter in different operating modes is given, and its boost factor is calculated. Then, the fundamental equations to design the values of inductors and capacitors are presented. Also, comparative analysis from different points of view, such as boost factor, voltage stresses on capacitors, and total voltage blocked by diodes and switches, between the proposed topology and conventional structures to examine the advantage and disadvantages is done. Comparison results show that the proposed topology has fewer voltage stresses on capacitors and total voltage blocked by diodes and switches. Also, it has fewer elements and continues input current and a more straightforward structure. The proposed topology's losses and efficiency at different loads are fully calculated. Finally, a prototype of the proposed topology is designed, and its experimental results along with simulation results by PSCAD to check the proposed topology's good performance and correctness of the obtained equations in different operating modes are provided.

Active impedance matching of a cryogenic radio frequency resonator for ion traps.

A combination of direct current (DC) fields and high amplitude radio frequency (RF) fields is necessary to trap ions in a Paul trap. Such high electric RF fields are usually reached with the help of a resonator in close proximity to the ion trap. Ion trap based quantum computers profit from good vacuum conditions and low heating rates that cryogenic environments provide. However, an impedance matching network between the resonator and its RF source is necessary, as an unmatched resonator would require higher input power due to power reflection. The reflected power would not contribute to the RF trapping potential, and the losses in the cable induce additional heat into the system. The electrical properties of the matching network components change during cooling, and a cryogenic setup usually prohibits physical access to integrated components while the experiment is running. This circumstance leads to either several cooling cycles to improve the matching at cryogenic temperatures or the operation of poorly matched resonators. In this work, we demonstrate an RF resonator that is actively matched to the wave impedance of coaxial cables and the signal source. The active part of the matching circuit consists of a varactor diode array. Its capacitance depends on the DC voltage applied from outside the cryostat. We present measurements of the power reflection, the Q-factor, and higher harmonic signals resulting from the nonlinearity of the varactor diodes. The RF resonator is tested in a cryostat at room temperature and cryogenic temperatures, down to 4.3K. A superior impedance matching for different ion traps can be achieved with this type of resonator.

Massive MIMO Precoding Methods That Minimize the Variation in Average Power and Active Impedance With Channel Conditions

This article investigates the impact of precoding on the performance of massive multiple-input multiple-output (mMIMO) transmitters exhibiting nonnegligible antenna crosstalk. For this, a new metric, called the average active impedance, is introduced to quantify the extent of load modulation as a function of the antenna S-parameters and the employed precoding. The new metric is then used to investigate the load modulation under conventional precoding schemes. It is shown that these precoders yield large disparities in average-power levels across the radio frequency (RF) chains, which results in substantial performance variations with channel conditions. Based on this investigation, we propose three new precoding schemes that yield equal average-power (EP) levels across all RF chains, independent of the channel conditions. Numerical simulations and experiments conducted on an mMIMO transmitter prototype confirmed that the proposed schemes improve the transmitter’s resilience to the variation in channel conditions.

An Adaptive Element-Level Impedance-Matched ASIC With Improved Acoustic Reflectivity for Medical Ultrasound Imaging.

This paper presents an active impedance matching scheme that tries to optimize electrical power transfer and acoustic reflectivity in ultrasound transducers. Leveraging negative capacitance-based impedance matching would potentially improve the bandwidth and electrical power transfer while minimizing acoustic reflection of transducer elements and improve uniformity while reducing acoustic crosstalk of transducer arrays. A 16-element transceiver front-end is designed which employs an element-level active capacitive impedance cancellation scheme using an element-level negative impedance converter. The ASIC fabricated in 180-nm HVBCD technology provides high-voltage pulses up to 60 V consuming 3.6 mW and occupying 2.5 mm2. The front-end ASIC is used with a 1-D capacitive micromachined ultrasonic transducer (CMUT) array and its acoustical reflectivity reduction and imaging capabilities have successfully been demonstrated through pulse-echo measurements and acoustic imaging experiments.

Plant Tissue Modelling Using Power-Law Filters.

Impedance spectroscopy has became an essential non-invasive tool for quality assessment measurements of the biochemical and biophysical changes in plant tissues. The electrical behaviour of biological tissues can be captured by fitting its bio-impedance data to a suitable circuit model. This paper investigates the use of power-law filters in circuit modelling of bio-impedance. The proposed models are fitted to experimental data obtained from eight different fruit types using a meta-heuristic optimization method (the Water Cycle Algorithm (WCA)). Impedance measurements are obtained using a Biologic SP150 electrochemical station, and the percentage error between the actual impedance and the fitted models’ impedance are reported. It is found that a circuit model consisting of a combination of two second-order power-law low-pass filters shows the least fitting error.

Electron enriched ternary NiMoB electrocatalyst for improved overall water splitting: Better performance as compared to the Pt/C || RuO2 at high current density

The high energy density and zero carbon emission makes the hydrogen energy most suitable for the next-generation alternative to reduce the greenhouse gas emissions and prevent the climate changes. In this work, the ternary nickel-molybdenum-boron (NiMoB) electrocatalyst is systematically studied and the best optimized NiMoB electrode demonstrates better electrochemical water splitting performance over the benchmark electrodes of Pt/C || RuO2 at high current density. Along with the systematic fabrication parameter optimization, the ternary NiMoB electrocatalyst with the multi-sphere morphology demonstrates significantly high active surface area, low impedance, and low reaction energy barriers with the improved crystallinity of electrodes and absorption and desorption of intermediates. The incorporation of boron in the transition metal matrix of Ni-Mo significantly boosts up the water splitting capability by lowering the kinetic barriers with the electron enriched metallic sites and improved stability of electrodes. Specifically, the turnover overpotential of 1.61 V is achieved at 50 mA/cm2 in 1 M KOH with the improved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics in a 2-electrode system. More importantly, the NiMoB electrocatalyst demonstrates better performances at high current range above 1250 mA/cm2 in 1 M KOH and 1100 mA/cm2 in seawater (SW) + 1 M KOH. The NiMoB || NiMoB also demonstrates an equivalent water splitting performance in the real SW + 1 M KOH solution. In addition, a very stable chronoamperometry (CA) operation over 12 h at 500 mA/cm2 and 1,000-time repetition of linear sweep voltammetry (LSV) over 8 h in 6 M KOH at 60 °C confirm that the optimized electrode can demonstrate stable and repetitive operations in an industrial electrochemical water splitting condition.

Convenient Synthesis of a Ru Catalyst Containing Single Atoms and Nanoparticles on Nitrogen-Doped Carbon with Superior Hydrogen Evolution Reaction Activity in a Wide pH Range.

Ruthenium, which is relatively cheap in precious metals, has become a popular alternative for a hydrogen evolution reaction (HER) catalyst because of its corrosion resistance and appropriate metal-H bond strength. Convenient synthesis and active site regulation are conducive to stimulating the excellent catalytic performance of Ru as much as possible. Herein, using the mature mesoporous nitrogen-doped carbon material as the support, the catalytic materials containing both single atom Ru and Ru nanoparticles were synthesized by impregnation using the solid-phase reduction method. The effect of reduction temperature on the dispersion state and electronic structure of Ru species has been fully studied using electronic and spectroscopic characterizations. The sample reduced at 300 °C has excellent HER activity with overpotentials of 10.8 and 53.8 mV to deliver 10 mA/cm2 in alkaline and acidic media, respectively, which is among the best activities in the reported results. Electrochemical impedance analysis shows that the reduction temperature has a great influence on the number of active sites and charge transfer impedance of the catalyst.

Lithium-Ion Battery Degradation: How to Diagnose It

Many different degradation mechanisms occur in lithium-ion batteries, all of which interact with one another [1]. However, there are few fewer observable consequences of degradation than there are mechanisms [2]. It is possible to measure the different degradation modes: loss of lithium inventory (LLI), loss of active material (LAM), impedance change and stoichiometric drift [3].It is not always possible to link these observable consequences of degradation to any particular mechanism or combination of mechanisms. Many models of degradation exist [4], but these models have many parameters that cannot be measured directly. A recent modelling study [5] found the number of parameters that the model is sensitive to is greater than the number of observable degradation modes.However, the same model [5], despite including just four degradation mechanisms, found five possible degradation pathways a battery can follow. The model was built so that more mechanisms can easily be added later, so more pathways will be found.In this work, a new approach to diagnosing battery degradation is proposed, based on these pathways. Experimental data for the degradation modes can be identified as being consistent with a particular pathway. Once the correct pathway is found, the parameters that particular pathway is sensitive to can be fit to the data, feeding back into the model.[1] Jacqueline Edge et al., Phys. Chem.: Chem. Phys. vol. 23, pp. 8200-8221, 2021.[2] Christoph Birkl et al., Journal of Power Sources vol. 341, pp. 373-386, 2017.[3] Matthieu Dubarry et al., J. Electrochem. En. Conv. Stor. vol. 17, pp. 044701, 2020.[4] Jorn Reniers et al., J. Electrochem. Soc. vol. 166 pp. A3189-A3200, 2019.[5] Simon O’Kane et al., Phys. Chem.: Chem. Phys., submitted, 2022. https://arxiv.org/abs/2112.02037

Fast capacity estimation for lithium-ion battery based on online identification of low-frequency electrochemical impedance spectroscopy and Gaussian process regression

Accurate capacity estimation is critical to improving the safety and reliability of lithium-ion (Li-ion) battery systems. Traditional capacity estimation mainly extracts capacity-related features by passively collecting the battery voltage, current, and temperature signals, which requires high integrity and regularity of charging curves. In this paper, six health indicators (HIs) are extracted through the online identification of Low-frequency electrochemical impedance spectroscopy (LEIS) by step wave, combined with Gaussian process regression (GPR) to achieve a fast capacity estimation for Li-ion batteries. The step wave is injected into the battery system during the charging process through BMS and bi-directional converter cooperation. Compared with square and multi-sine waves, the stress and response of each frequency step wave are equivalent to that of the sine wave. Moreover, HIs are resolved from the actual Warburg impedance angle instead of the empirical angle π/4. Three novel HIs related to the Li-ion diffusion coefficient are proposed: Warburg factor Wd, pseudo-Li-ion diffusion state PLDS and residual signal of empirical mode decomposition PLDSr. The volume of GPR training data is only 34% of the whole frequency band EIS data. The results show that the identified LEIS achieves 0.96 goodness-of-fit (R2) at the minimum sampling frequency of 50 Hz, and the novel HIs significantly improve the state of health (SOH) estimation accuracy with R2 above 0.95, root mean squared error below 1%, and mean absolute percentage error of about 0.9%. This method is an effective way to the active SOH detection for Li-ion battery, which is vital for the online SOH evaluation and early safety warning.

The role of the electrical percolation threshold on the anticorrosion performance of an aqueous polyurethane dispersion containing polyaniline

In this study, the anticorrosion properties of a waterborne polyurethane dispersion (WPU) containing polyaniline (PAni) were investigated and discussed considering the electrical percolation threshold (EPT) of this mixture. For that, easily dispersible poly(styrene sulfonic acid)-doped PAni (PAni:PSS) was incorporated into an anionic WPU at contents ranging from 1 to 8 wt%. Free-standing films of PAni:PSS/WPU reached the EPT at 6 wt% (4.8 v.%) of PAni:PSS. The mixtures remained stable and without signs of PAni dedoping. Based on the electrical behavior curve, PAni:PSS/WPU coatings were prepared below (1, 2, 3 wt%), close to (5 wt%), at (6 wt%) and above the EPT (8 wt%). The coatings were applied on ground low-carbon steel panels and evaluated regarding their contact angle, adhesion, and anticorrosion performance in electrochemical tests. The coatings prepared below the EPT presented higher hydrophobicity, good wet adhesion, and higher open circuit potential (OCP) and impedance modulus in the low frequency range (|Z|10 mHz). The best overall performance was achieved at 3 wt% of PAni:PSS which presented OCP values in the range of 34 ± 11 mV for 144 h and initial |Z|10 mHz of 108 Ω.cm2. These coatings also presented a colorimetric feature of changing color as the corrosion progressed. Meanwhile, the coatings containing PAni:PSS quantities close, at and above the EPT, i.e., at 5, 6 and 8 wt% presented high porosity, poor wet adhesion, and intense blistering. They also presented OCP values in the region of active corrosion and impedance spectra typical of coatings with poor barrier properties. These results indicate that, the formation of conducting networks within the insulating matrix is not necessarily a condition that must be met for a coating containing PAni achieve an optimal anticorrosion performance.

Study on Impact of Mutual Coupling on Performance of Dual Polarized Phased Array Antenna

This study involves the determination of the impact of mutual coupling between antenna elements on the performance of a dual-polarized, wide-angle scanning, phased array antenna for weather radar applications. Weather radars require dual linearly polarized antennas with low cross-polarization, and a narrow beam phased array for wide scanning angle. For this simulation-based study, a microstrip dual linearly polarized 2x20 phased array antenna operating at S-band (2.65 to 3.0 GHz) is designed. This antenna has been designed to have a cross-polarization level less than -45 dB at both polarizations and for the scan angle range of -55o to 55o, which is better than most of the existing dual-pol phased array antennas. This antenna has been used to analyze the impact of mutual coupling on cross-polarization, beamwidth, and antenna gain at various scan angles. Mutual coupling is studied in terms of antenna active element pattern and the corresponding cross-polarization value as well as the active reflection coefficient and impedance values for inter-element spacings of 0.4λ and 0.5λ. It has been found in this study that cross-polarization levels of the whole array (at various scan angles) are affected significantly because of mutual coupling between elements.

Current References Limitation Method Considering Voltage and Current Maximums for STATCOMs Providing Simultaneously Reactive Power and Current Harmonics

This article focuses the analysis on a static synchronous compensator (STATCOM) that operates simultaneously providing reactive power and several current harmonics of different frequencies (active power filter or active impedance functionalities). Being more specific, this article proposes a general limitation method that reduces the current references of the STATCOM whenever the current or voltage limit of the converter is exceeded. In a realistic operation scenario, the STATCOM’s operator may ask for certain reactive power and harmonic current reference signals, and depending on the actual grid voltage conditions (unbalances and harmonics), the required converter voltage and current may exceed their limit. Consequently, the proposed limitation method protects the STATCOM system from malfunctioning when the voltage limit is exceeded and from damages when the current limit is exceeded. Hence, this article first proposes a limitation method oriented to a STATCOM that operates solely exchanging reactive power. Second, the limitation method is generalized for a STATCOM that controls reactive power as well as several current harmonics. Then, simulation and experimental results are provided to validate the proposed limitation method, under a rich variety of working conditions. Finally, a conceptual analysis of the method is carried out confronting it against several possible limitation alternatives.

Power-Shaping Model-Based Control With Feedback Deactivation for Flexible-Joint Robot Interaction

This letter presents a novel control methodology that is based on an amalgamation of model-based, power-shaping control (PSC), and feedback deactivation. It has been hypothesised that proportional position control of flexible-joint robots can impinge on their interactional performance, since position feedback causes a ‘stiffening’ of the robot's joints. In order to reduce reliance upon feedback terms, this work proposes usage of feedforward, model-based control terms, whilst accounting for both the actuator and link coordinates. The introduced PSC signal enables stable tracking control, even when the proportional controller's position error term employs solely non-collocated state feedback. It is also demonstrated that the user can stably deactivate position feedback pertaining to specific joints, in a real-time manner, so as to further enhance interactional performance. However, since feedback deactivation can lead to abrupt generation of unfeasible control signals, a variable impedance control (VIC) technique is proposed to overcome this limitation. Despite VIC's potential to inject undesirable amounts of energy into the closed-loop system, an amended PSC term is introduced to guarantee stability preservation. Moreover, to achieve saturation prevention in an energy efficient manner, a novel Lyapunov function is proposed that enables unconstrained modulation of the system's active impedance gains. Experimental results involving the Rethink Robotics Baxter robot corroborate the theoretical stability analyses, in addition to demonstrating that interactional and tracking performance improvements can be achieved via the proposed methodology.

Reduced Switch Voltage Stress Ultra-Gain DC-DC Converter for High Voltage Low Power Applications

An ultra-voltage gain dc-dc converter is proposed in this brief using an active impedance network with a single MOSFET switch. The proposed converter utilizes minimum components and achieves the ultra-gain with lower switch voltage stress. The general structure of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula> -stage active switched impedance topology is presented, and the detailed operation of the basic converter configuration is discussed. The components of the converter are designed using proper mathematics, and a 200 W, 50 kHz, 650 V lab-scale hardware prototype is fabricated. The dynamic model of the converter is derived, and the transfer function <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\hat {v}_{0} / \hat {d}} $ </tex-math></inline-formula> is presented. The testing of the 200 W prototype has been done, and the experimented waveforms are shown. Reduced components, lower voltage stress, ultra-voltage gain and single MOSFET are the major merits of the proposed converter; hence the converter has a potential application in high-voltage low power systems.

Active Admittance and Impedance of Hexagonally Sampled Dipole and Slot Connected Arrays

Active Admittance and Impedance of Hexagonally Sampled Dipole and Slot Connected Arrays

Fault Location and Classification for MVDC Networks

This paper proposes a two step fault detection scheme for medium-voltage dc (MVDC) networks based on wavelet analysis. The proposed Grid Transients Classifier (GTC) is used to continuously monitor energy of wavelet packet decomposition levels (WPDL) for voltage and current signals to determine any transient disturbance like load change, pole to pole (PP) or pole to ground (PG) faults, pole to pole to ground (PPG), voltage sags, switching, etc. Subsequently, type of disturbance is identified through an artificial neural network (ANN) classifier. Then, proposed Active Grid Impedance Estimator (AGIE) injects a signal with two fundamental frequencies to evaluate grid impedance from the measurement point in new condition. Using the obtained data, fault type, location and its severity are specified. Hardware-in-the-Loop (HIL) results are provided for a shipboard grid case study to validate the real-time application of the proposed method and demonstrate its effectiveness.

Equivalent circuit model of a non-faradaic impedimetric ZnO nano-crystal biosensor

• Sensing of C-reactive protein using a novel co-planar electrode PET-ZnO biosensor. • Development of an EEC model of the biosensor platform. • EEC modelling demonstrates predicted properties of a non-faradaic biosensor. • Quantified EDL charge modulations arising due to CRP binding at the ZnO surface. • Dominance of each sensor component identified to support control of parasitics. This paper describes the development of an equivalent electrical circuit (EEC) model of a unique co-planar electrode PET-ZnO biosensor platform. This non-faradaic ZnO biosensor had a PET insulating layer between the electrodes and the active ZnO sensor surface and impedance spectroscopy was used to measure varying concentrations of C-reactive protein (CRP). Analysis of the impedance magnitude bode plot reveals a slope indicative of a capacitive behaviour, where R 2 is 0.99. Furthermore, extraction of the complex impedance parameters shows capacitive reactance (Xc) being the dominant parameter as a result of capacitive transduction mechanism. The EEC was based on the generalized Randles model and adapted to represent the non-faradaic ZnO biosensor. Experimental data was fitted to the model at 100 kHz to establish values for the component parts of the biosensor system. With these values the model showed good correlation between experimental and modelled data across the frequency range studied, within the limitations of the measurement instrument. The model quantified charge modulations arising due to bimolecular binding of CRP within the electrical double layer (EDL) formed at the ZnO-PBS interface. The CRP bio-molecular interaction within the EDL can cause high charge carrier density accumulation in the semiconductor and as a result the capacitance of the EDL is increased. The EEC model quantifies this phenomenon, presented as a parallel capacitance connected to the ZnO-Antibody interfacial capacitance. The model was adapted to two variants of the biosensor design, with differing ZnO nanoparticle concentrations forming the sensor surface. The variations on the components modelled concurred with expected changes established from biosensor surface analysis. Using the EEC model, the dominance of each constituent sensor element on measurement stability is quantified identifying the significant contributors to experimental and sensor-to-sensor repeatability to support control of parasitic effects.

PID-like active impedance control for electroacoustic resonators to design tunable single-degree-of-freedom sound absorbers

Sound absorption at low frequencies still remains a challenge in both scientific research and engineering practice. Natural porous materials are ineffective in this frequency range, as well as acoustic resonators which present too narrow bandwidth of absorption, thus requiring alternative solutions based on active absorption techniques. In the present work, we propose an active control framework applied on a closed-box loudspeaker to enable the adjustment of the acoustic impedance at the loudspeaker diaphragm. More specifically, based on the proportionality between the pressure inside the enclosure and the axial displacement of the loudspeaker diaphragm at low frequencies, we demonstrate both analytically and experimentally that a PID-like feedback control approach allows tuning independently the compliance, the resistance and the moving mass of the closed-box loudspeaker to implement a prescribed impedance of a single-degree-of-freedom resonator. By considering different control combinations to tailor the resonator characteristics, a perfect absorption (with absorption coefficient equal to 1) is achievable at the target resonance frequency, while enlarging the effective absorption bandwidth. Moreover, the proposed feedback control strategy shows an excellent control accuracy, especially compared to the feedforward-based control formerly reported in the literature. The mismatches between the performance of experimental prototype and the model, likely to result from the control time delay and the inaccuracy in estimating the loudspeaker parameters, can be compensated directly by tuning the control parameters in the control platform. The active resonators implemented through the reported control scheme can be used to build more complex acoustic devices/structures to enable high-efficiency broadband sound absorption or other types of acoustic phenomena such as wavefront shaping.

Research on the Resonance Suppression Method for Parallel Grid-Connected Inverters Based on Active Impedance

Under the condition of weak grid, the coupling between parallel inverters and grid impedance is easy to cause harmonic resonance, which seriously affects the grid-connected power quality. First, the equivalent circuit model of the multi-inverter parallel system is established, and the mechanism of harmonic resonance is analyzed from the perspective of impedance; through the resonance detection method based on a self-tuning filter, the voltage resonance component of the parallel node is extracted; on that basis, an active impedance is designed to suppress the resonance of the multi-inverter parallel system, which can equivalently construct a virtual impedance branch to improve the grid impedance characteristics at the resonance frequency, and its effectiveness is verified using the impedance stability criterion. Finally, simulation experiments are carried out. The results show that this method can effectively suppress the resonance of the multi-inverter parallel system and can significantly improve the adaptability of inverters to weak grid.

Full Lumped Element-Based Equivalent Circuit Model for Connected Slot Antenna Arrays

A full lumped element-based equivalent circuit model for connected slot antenna arrays (CSAA) is proposed with three configurations of the CSAA being considered: infinite, semi-infinite, and finite slots. First, an equivalent circuit model was developed from the available Green’s Function (GF) based analytical expression of the active impedance of CSAA. It was demonstrated that by combining PI or T networks with parallel RLC resonant circuits and modeling the higher order modes via the series inductor, the active impedance and the reflection characteristics of the CSAA can be represented in an efficient and accurate manner. Secondly, utilizing the proposed equivalent circuit model, a generalized design procedure was developed to assist the design and analysis of arbitrary configurations of CSAA at both microwave and millimeter wave (mm-wave) bands. Finally, the effectiveness and accuracy of the proposed approach are validated by several numerical and measured results. A 2x2 CSAA prototype was fabricated at 3 GHz to validate the proposed equivalent circuit model. For the finite slot case, the proposed RLC+T network outperforms both the available transmission line-based equivalent circuit model and the proposed RLC+PI network, in describing the resonance frequencies and the values of the impedances of the finite slot. It was demonstrated that the proposed equivalent circuit model had a maximum of 4.55% and 5.27% average errors for the real and imaginary parts of the impedances, as compared with the full-wave simulator, while the computational time was reduced by more than two orders of magnitude.