Showing papers on "Output impedance published in 2023"
TL;DR: In this paper , a correction method of series virtual impedance is proposed, which connects the inductive link in a series configuration with the inverter output impedance, correcting the inverters equivalent output impedance from resistance-capacitance to resistance-inductance and improving the system stability margin.
Abstract: The regenerative braking in the tram allows the energy to be returned to the power grid through a power inverter. Since the inverter location between the tram and the power grid is not fixed, resulting in a wide variety of impedance networks at grid coupling points, posing a severe threat to the stable operation of the grid-tied inverter (GTI). By independently changing the loop characteristics of the GTI, the adaptive fuzzy PI controller (AFPIC) can adjust according to different impedance network parameters. It is challenging to fulfill the stability margin requirements of GTI under high network impedance since the PI controller has phase lag characteristics. A correction method of series virtual impedance is proposed, which connects the inductive link in a series configuration with the inverter output impedance, correcting the inverter equivalent output impedance from resistance-capacitance to resistance-inductance and improving the system stability margin. Feedforward control is adopted to improve the system's gain in the low-frequency band. Finally, the specific series impedance parameters are obtained by determining the maximum network impedance and setting the minimum phase margin of 45°. The realization of virtual impedance is simulated by conversion to an equivalent control block diagram, and the effectiveness and feasibility of the proposed method are verified by simulation and a 1 kW experimental prototype.
4 citations
TL;DR: In this paper , a variable-operating point impedance model (VOPIM) of a VSC is derived to determine the frequency and damping of the oscillation modes for varying operating points.
Abstract: The interactions between voltage-sourced converters (VSCs) and the grid may trigger unstable electromagnetic oscillations. Impedance model-based analysis is widely utilized for investigating such emerging stability issues, mainly due to its capability to model black/gray-box VSC-based devices without complete knowledge of their internal control structures and parameters. It is well known that the characteristics of the triggered oscillation are determined by the operating conditions. However, most of the existing impedance-based methods are operating point specific, i.e., the impedance model of VSC-based devices has to be re-measured upon variations in the operating point. Thus, it is quite cumbersome and hectic to reconstruct the impedance model of a VSC-based device for all possible operating points and establish a stable or unstable region. This paper develops a novel method to determine the oscillatory stability region of a grid-tied VSC. First, a variable-operating point impedance model (VOPIM) of a VSC is derived. Next, the VOPIM is used to determine the frequency and damping of the oscillation modes for varying operating points. Finally, the oscillatory stability region is determined according to the damping of each oscillation mode. The accuracy of the oscillatory stability region and the effectiveness of the proposed method is verified through time-domain electromagnetic simulations.
3 citations
TL;DR: In this paper , a physics-informed neural network based impedance identification is proposed to fill this research gap, where the physics knowledge of the VSC is used to compress the artificial neural network, which can reduce the calculation burden of online impedance identification.
Abstract: The wide integration of voltage source converters (VSCs) in power grids as the interface of renewables causes the converter-grid interaction stability challenge. The black-box impedance of VSCs identified at the converter terminal is the key to facilitate the study of converter-grid interaction stability. However, since the limited impedance data amount in online measurement, the existing impedance identification methods cannot accurately capture characteristics of the impedance model in various operating scenarios with the changing profiles of renewables and loads. In this article, a physics-informed neural network based impedance identification is proposed to fill this research gap. The physics knowledge of the VSC is used to compress the artificial neural network, which can reduce the calculation burden of online impedance identification. Meanwhile, the two-steps impedance identification is developed with the inspiration of the transfer learning theory to further increase the online impedance identification efficiency. This method can significantly reduce the required data amount used in online impedance identification for the online stability analysis with the changing operating points. The case studies confirm the effectiveness of the proposed method.
3 citations
TL;DR: In this paper , the authors proposed a high-frequency fault analysis-based pilot protection scheme, in which the range of frequency employed for protection (FEP) is analyzed theoretically.
Abstract: Due to the influence of inverter control, the short-circuit current provided by distributed photovoltaics (PVs) exhibits new characteristics, such as a controlled amplitude and phase angle, resulting in the malfunction of the current protection and differential protection of distribution networks with high PV penetration. In this paper, the equivalent high-frequency impedance model (EHFIM) of PV power generation and the analysis method of a fault high-frequency superimposed network are proposed. On this basis, we analyze the fault high-frequency superimposed network of a distribution network with high PV penetration and propose a high-frequency fault analysis-based pilot protection scheme, in which the range of frequency employed for protection (FEP) is analyzed theoretically. By comparing the relationship between the high-frequency operating impedance and the high-frequency restraining impedance, the internal and external faults are identified. The proposed protection scheme has the advantages of a fast trip, low requirement for data synchronization, immunity to inverter control and the PV operation mode, and adaptability to lines with teed feeders. The experimental results show that the proposed protection scheme can accurately identify internal and external three-phase, two-phase, and two-phase grounding faults and is resistant to both fault resistance and noise interference.
2 citations
TL;DR: In this article , a generalized impedance model in the dq frame is developed to facilitate the impedance-based analysis of any grid node with both grid-following (GFL) and grid-forming (GFM) converters.
1 citations
TL;DR: In this article , a dual-stage boost converter circuit was proposed to facilitate self-powering features and boost the low voltage harvested by the piezoelectric devices into dc. The proposed circuit comprises conversion stages of ac-dc and dc-dc in stages I and II.
Abstract: Miniaturised piezoelectric devices are emerging energy harvesting sources that are appropriate for various implantable and wearable applications. However, these piezoelectric devices exhibit considerable internal resistance due to their internal impedance, which leads to self-start and low-energy conversion failures. This paper describes a dual-stage boost converter circuit by facilitating self-powering features and boosting the low voltage harvested by the piezoelectric devices into dc. The proposed circuit comprises conversion stages of ac-dc and dc-dc in Stages I and II, respectively. In addition, the proposed circuit does not require employing the auxiliary circuits to generate the train pulses by triggering the bidirectional switches to envelop the current being stored in Stage II and kick-start the self-powered circuit for piezoelectric energy harvesting systems. Theoretical assumptions and control strategies were tested and verified with ideal and impedance input sources. The proposed circuit could convert a low voltage of 3 Vac into 19 Vdc. The maximum attained output power by the proposed circuit was 3.61 mW. The outcome depicted that the proposed circuit boosted the low voltage and outperformed the existing literature circuits in terms of output voltage and power.
1 citations
TL;DR: In this article , a low quiescent current structure of high voltage LDO with self-regulation impedance buffer and bandgap amplifier is presented, where the function of voltage reference and error amplifier can be achieved simultaneously.
Abstract: Abstract To improve the whole characteristic of the LDO, a low quiescent current structure of high voltage LDO with self-regulation impedance buffer and bandgap amplifier is presented in this paper. With the bandgap amplifier proposed, the function of voltage reference and error amplifier can be achieved simultaneously, which can efficiently reduce the consumption. The load capacitor can be as small as 0.47µF by using the self-regulation impedance buffer and current buffer compensation scheme. The LDO has been implemented in a 0.18 µm process with die size 0.03 mm2 . Without the load, the consumption quiescent current of the LDO is 1 µA. Experimental result shows that the overshoot and undershoot of line transient response are less than 30 mV/V. The load regulation is about 0.1A, and line regulation is about 0.07 mV/V at no load condition.
15 May 2023
TL;DR: In this article , an improved Howland current pump circuit was chosen as a suitable solution for the current source in order to select an amplitude value suitable for accuracy and in the frequency range of 0.1 Hz - 200 kHz.
Abstract: The article is devoted to the development of a broadband electric current source for the purposes of impedance study of cell cultures. The impedance methods for cell study were analysed. The problem of high (up to $10 \mathbf{M}\boldsymbol{\Omega})$ resistance of electrodes for cell research was determined. An analysis of existing circuit solutions for the current source was carried out in order to select an amplitude value suitable for accuracy and in the frequency range of 0.1 Hz - 200 kHz. An improved Howland current pump circuit was chosen as a suitable solution. To confirm the characteristics, simulations were carried out in the Multisim environment in the frequency range of 0.1 Hz - 200 kHz. The results of the simulations showed that the improved Howland circuit, when using a buffer in the feedback circuit, has an error in setting the amplitude of the load current of 0.422%. Additional Monte-Carlo analysis showed that with the 0.05% tolerance of passive components values the error in setting the amplitude of the load current is 1.4%.
TL;DR: In this article , four possible matching network structures are designed by the Smith diagram circle method, and two kinds of capacitor structures are calculated and analyzed, and the influence of capacitance change on impedance matching state is analyzed.
Abstract: The radio frequency (RF) ion source is the key component of the neutral beam injector to achieve high power and long pulse operation. The key technology is feeding RF power from the power source to the ion source and producing stable plasma. It is impossible to calculate the exact equivalent impedance of plasma during discharge, and the impedance will change with the change in discharge pressure and feed power. In order to transfer the maximum output power of the RF power source to the coil antenna of the ion source, an impedance-matching network must be added between the power source and the ion source. Four possible matching network structures are designed by the Smith diagram circle method, and two kinds of capacitor structures are calculated and analyzed. The influence of capacitance change on impedance matching state is analyzed, and the electrical parameters of capacitance under the two structures are compared. After comparison and analysis, the structure of the parallel capacitor is first, and then the series capacitor is selected. Finally, the plasma discharge can be stable through experiments. The research on the matching network is of great significance for the development and experimental operation of the RF feeding system of the high-power RF ion source in the future
13 Jun 2023
TL;DR: In this paper , a direct current power supply circuit (DPS) was proposed to match the impedance of the freestanding-sliding mode triboelectric nanogenerator (FS-TENG) with multi-harmonic characteristics and continuously supply power to the load with reduced energy loss.
Abstract: This study proposes a direct current power supply circuit (DPS) that can match the impedance of the freestanding-sliding mode triboelectric nanogenerator (FS-TENG) with multi-harmonic characteristics and continuously supply power to the load with reduced energy loss. The proposed DPS consists of a double charge circuit (DCC) and a DC conversion circuit based on a comb filtering circuit (CFC). The proposed DPS successfully matched the high internal impedance of the FS-TENG, collected multi-harmonic electrical energy, and provided stable DC voltage for practical applications in real-time. The proposed FS-TENG and DPS supplied a continuous DC voltage of 2.2 V to loads with 0.039 % ripple, while reducing the impedance of the TENG from 221 MΩ to 11 MΩ. The present results demonstrate that the proposed DPS has higher output power than conventional buck and buck-boost converters for the FS-TENG with high impedance and multi-harmonic characteristics. This work presents a significant advancement towards continuous DC power supply utilizing the FS-TENG. In addition, the practical application of the FS-TENG and DPS was successfully demonstrated to drive a self-powered temperature sensor in real-time by generating a constant DC output voltage across a thermistor.
TL;DR: In this article , a discrete-interval-binary sequence (DIBS) was proposed to measure the battery impedance in order to estimate the state-of-charge (SOC) and SOH (SOH) of Li-ion batteries.
Abstract: State parameters such as the state-of-charge (SOC) and state-of-health (SOH) play important role in the operation of Li-ion batteries, and accurate estimate of the parameters is of prime importance in evaluating the battery condition and guaranteeing the safe use. While it is difficult to measure the SOC and SOH directly, the battery internal impedance can be used to obtain the parameters. Recent studies have shown methods based on pseudo-random binary sequence (PRBS) with which the battery impedance can be rapidly measured in real time. Using this method, the battery is charged and recharged according to the excitation waveform and Fourier methods are applied to obtain the impedance. The PRBS often produces accurate impedance measurements, but the method may require a high perturbation amplitude, which may easily interfere with the nominal battery operation and create nonlinear distortions. This paper proposes the use of discrete-interval-binary sequence (DIBS) for measuring the battery impedance. The DIBS is a computer-optimized binary sequence in which the power spectral densities are maximized at specified frequencies without increasing the signal time-domain amplitude. Experimental measurements of a commercial Li-ion battery are presented to demonstrate the effectiveness of the proposed method.
TL;DR: In this article , an active electrode and back-end integrated system for enhanced electrocardiogram (ECG)/electrode-tissue impedance (ETI) measurement is proposed.
Abstract: An active electrode (AE) and back-end (BE) integrated system for enhanced electrocardiogram (ECG)/electrode-tissue impedance (ETI) measurement is proposed. The AE consists of a balanced current driver and a preamplifier. To increase the output impedance, the current driver uses a matched current source and sink, which operates under negative feedback. To increase the linear input range, a new source degeneration method is proposed. The preamplifier is realized using a capacitively-coupled instrumentation amplifier (CCIA) with a ripple-reduction loop (RRL). Compared to the traditional Miller compensation, active frequency feedback compensation (AFFC) achieves bandwidth extension using the reduced size of the compensation capacitor. The BE performs three types of signal sensing: ECG, band power (BP), and impedance (IMP) data. The BP channel is used to detect the Q-, R-, and S-wave (QRS) complex in the ECG signal. The IMP channel measures the resistance and reactance of the electrode-tissue. The integrated circuits for the ECG/ETI system are realized in the 180 nm CMOS process and occupy a 1.26 mm2 area. The measured results show that the current driver supplies a relatively high current (>600 μApp) and achieves a high output impedance (1 MΩ at 500 kHz). The ETI system can detect resistance and capacitance in the ranges of 10 mΩ–3 kΩ and 100 nF–100 μF, respectively. The ECG/ETI system consumes 3.6 mW using a single 1.8 V supply.
TL;DR: In this article , a general parameter design outline for droop-controlled inverters is proposed to simplify the complicated parameter tuning task while assuring good performances, based on which the effects of parameters on impedance characteristics and power stability are analyzed in detail.
TL;DR: In this paper , a low-noise amplifier (LNA) with an integrated input and output matching network designed using RF-SOI technology was designed with a resistive feedback topology and an inductive peaking technology to provide 600 MHz of bandwidth in the N79 band.
Abstract: This paper presents a low-noise amplifier (LNA) with an integrated input and output matching network designed using RF-SOI technology. This LNA was designed with a resistive feedback topology and an inductive peaking technology to provide 600 MHz of bandwidth in the N79 band (4.4 GHz to 5.0 GHz). Generally, the resistive feedback structure used in broadband applications allows the input and output impedance to be made to satisfy the broadband conditions through low-impedance feedback. However, feedback impedance for excessive broadband characteristics can degrade the noise performance as a consequence. To achieve a better noise performance for a bandwidth of 600 MHz, the paper provided an optimized noise performance by selecting the feedback resistor value optimized for the N79 band. Additionally, an inductive peaking technique was applied to the designed low-noise amplifier to achieve a better optimized output matching network. The designed low-noise amplifier simulated a gain of 20.68 dB and 19.94 dB from 4.4 to 5.0 GHz, with noise figures of 1.57 dB and 1.73 dB, respectively. The input and output matching networks were also integrated, and the power consumption was designed to be 9.95 mA at a supply voltage of 1.2 V.
TL;DR: In this paper , a low-voltage low-power fully differential class AB current output stage with high linearity and unique current drive capability is presented, which can deliver the ever high output current of ±350 mA with THD of −49 dB and output impedance of 2.8 MΩ, which leads to a unique high current drive ratio of 10,000 and low consumed power of 150 µw in pre-layout simulation.
Abstract: This paper presents a novel low-voltage low power fully differential class AB current output stage with high linearity and unique current drive capability. The proposed circuit is based on a simple and efficient structure to obtain high linearity by minimising the channel length modulation effect and also avoids cascade structure to act best in low-voltage applications. Giving the complete analyses and equations of the circuit, its properties are verified by Cadence using TSMC 0.18 µm CMOS parameters. In order to study its performance at the presence of non-idealities, Pre-layout and Post-layout both plus Monte–Carlo simulations are also performed. Under±0.9 V supply and 35 µA output bias current, it can deliver the ever high output current of ±350 mA with THD of −49 dB and output impedance of 2.8 MΩ, which leads to a unique high current drive ratio (Ioutmax/Ibias) of 10,000 and low consumed power of 150 µw in pre-layout simulation. In post-layout plus Monte–Carlo simulation, the results will be as ±320 mA output current, −42 dB THD, 2.2 MΩ output impedance, 40 µA DC current of the output branch, 8000 current drive ratio and 160 µw consumed power. These remarkable results prove the proposed novel COS not only as the unique one in the world but Longley ahead of the yet second rank COS by some unbeatable ratios as 11300×,14×,4× and3× in FT, Ioutmax, (Ioutmax/power), and current drive, respectively, that promise to keep it as the lead one for many years in low-voltage/power ultra-high current applications.
TL;DR: In this article , the intrinsic mechanism of batteries and the influence of non-stationary conditions on impedance were discussed and an online adaptive adjustment of model parameters was achieved using the forgetting factor recursive least squares algorithm and varied parameters approach (VPA) algorithm.
Abstract: Models play a crucial role in explaining internal processes, estimating states, and managing lithium-ion batteries. Electrochemical models can effectively illustrate the battery’s mechanism; however, their complexity renders them unsuitable for onboard use in electric vehicles. On the other hand, equivalent circuit models (ECMs) utilize a simple set of circuit elements to simulate voltage–current characteristics. This approach is less complex and easier to implement. However, most ECMs do not currently account for the nonlinear impact of operating conditions on battery impedance, making it difficult to obtain accurate wideband impedance characteristics of the battery when used in online applications. This article delves into the intrinsic mechanism of batteries and discusses the influence of nonstationary conditions on impedance. An ECM designed for non-steady state conditions is presented. Online adaptive adjustment of model parameters is achieved using the forgetting factor recursive least squares (FFRLS) algorithm and varied parameters approach (VPA) algorithm. Experimental results demonstrate the impressive performance of the model and parameter identification method, enabling the accurate acquisition of online impedance.
TL;DR: In this paper , a current source for the electrical impedance tomography with compensation in output resistance drop, its block diagram was shown and its hardware implementation was described, and a technique for assessing the stability of the current source output parameters, a comparison of current sources with and without compensation for the drop in output resist and amplitude, respectively, has been carried out.
Abstract: The article considers a current source for the electrical impedance tomography with compensation in output resistance drop, its block diagram being shown, and its hardware implementation being described. It also presents a technique for assessing the stability of the current source output parameters, a comparison of current sources with and without compensation for the drop in output resistance and amplitude, respectively, has been carried out. It is con-cluded that for a given amplitude of the output current in a given range of frequencies and resistances, a current source with an output resistance drop compensation circuit has an error an order of magnitude smaller than a traditional current source with the same circuitry, and this will positively affect the metrological characteristics of the en-tire electrical impedance tomography device.
27 Feb 2023
TL;DR: In this article , a gallium nitride (GaN) variable-gain low-noise amplifier (VGLNA) using a stacked-cascode current steering architecture is presented.
Abstract: This work presents a gallium nitride (GaN) variable-gain low-noise amplifier (VGLNA) using for the first time a stacked-cascode current steering architecture. The simulation results show that an extensive gain variation range can be achieved without degrading other key performance parameters. This technique significantly outperforms the capabilities of VGLNAs based on controlling the biasing voltage of the amplifying transistor, which is limited by a notable input impedance mismatching.
TL;DR: In this article , a general, efficient, and accurate modeling technique is presented, whose framework supports both current-mode PWM and adaptive on-time (AOT) controllers, which can be used to evaluate the equivalent values of internal feedback parameters of an encrypted simulation model or from measurement.
Abstract: Accurate evaluation and simulation of power noise is critical in the development of modern electronic devices. However, the widely used target impedance fails to predict the low-frequency noise generated in a device due to the existence of the dc–dc converter, whose output impedance can change under different loading conditions. A physical circuit model is then desired to replicate the behavior of a voltage regulator module, and the average technique is an efficient method to estimate the noise of a pulsewidth-modulated (PWM) converter. With the emergence of converters with adaptive on-time (AOT) controllers, more complex averaging methods are required, but none of them supports transient simulation. A general, efficient, and accurate modeling technique is presented in this article, whose framework supports both current-mode PWM and AOT controllers. In addition, a novel two-step parameter extraction method is proposed, which can be used to evaluate the equivalent values of internal feedback parameters of an encrypted simulation model or from measurement. The modeling method is validated by both simulation and measurement.
TL;DR: In this paper , a new family of magnetically coupled impedance source inverters with a smooth dc-link voltage, a low ST current, and a higher voltage gain is proposed.
Abstract: The use of coupled inductors in impedance source inverters improves the voltage gain performance at the expense of high dc-link voltage spikes and shoot-through (ST) currents. The result is an increase in voltage and current stresses on semiconductors, as well as reactive element capacity and overall losses. Thus, to overcome these problems, this letter proposes a new family of magnetically coupled impedance source inverters with a smooth dc-link voltage, a low ST current, and a higher voltage gain that are confirmed through experimental tests.
TL;DR: In this article , an internal voltage robust control of battery energy storage system for suppressing the wideband harmonics, which can achieve the voltage stability control of islanded microgrids under load disturbance.
Abstract: In constant voltage and frequency (VF) control-based islanded microgrids, the nonlinear load can easily cause voltage harmonics and degrade the power quality of the islanded microgrids. Firstly, the mechanism and characteristics of the voltage distortion are analyzed based on the impedance method. Due to the large internal impedance of the energy storage inverter, the harmonic voltage generated on the internal resistance is relatively large, leading to the microgrids' voltage distortion. To address this issue, this paper proposes an internal voltage robust control of battery energy storage system for suppressing the wideband harmonics, which can achieve the voltage stability control of islanded microgrids under load disturbance. Compared with the traditional energy storage inverter, the impedance amplitude of the improved inverter is relatively small, which is more like an ideal voltage source. Under the nonlinear load and pulse load disturbances, the voltage of the islanded microgrids controlled by the proposed control strategy can operate normally. Finally, the effectiveness of the proposed control strategy and the above theoretical analysis is verified by simulation and experiment.
01 Jan 2023
TL;DR: In this article , a multichannel EIS system was used to identify an equivalent circuit of an Industrial Scale Vanadium Redox Flow Battery (IS-VRFB) stack with a rated power/energy of 9 kW/27 kWh.
Abstract: The work provides early results obtained with a multichannel EIS system, which were used to identify an equivalent circuit of an Industrial Scale Vanadium Redox Flow Battery (IS-VRFB) stack with a rated power/energy of 9 kW/27 kWh. The single cell impedance is represented with three different models, including a series resistance and an RC loop (RRC model), or a constant phase element (CPE) loop (a ZARC element), or a ZARC element including also a Warburg impedance. The inclusion of the CPE constitutes a substantial improvement in the fit. Conversely, the addition of the Warburg element, which aims to model the mass transfer in the electrochemical process, does not produce significant effects for the frequencies at which we have experimental data. This numerical results are validated against EIS measurements taken on IS-VRFB. Very few analyses of this type are reported in the literature for such batteries. This study set the stage for developing advanced online State of Health (SOH) management for IS-VRFB.
TL;DR: In this article , an adaptive low-frequency harmonic current suppression method based on impedance editing of the source-stage dc-dc converter is proposed, which does not require additional circuits, which will never decrease the system efficiency but reduce the cost.
Abstract: In the two-stage inverter, a large amount of low-frequency harmonic current will emerge in the front-end dc–dc converter and input dc voltage source. The low-frequency harmonic current will reduce the service life of the dc source and decrease the efficiency of the system. Additionally, the main components of low-frequency harmonic current fluctuate with uncertainty. To address those issues, an adaptive current suppression method based on impedance editing of the source-stage dc–dc converter is proposed in this article. Compared with the traditional active power filter (APF), the proposed adaptive low-frequency harmonic current suppression method does not require additional circuits, which will never decrease the system efficiency but reduce the cost. More importantly, when the amplitude of the main components of harmonic current fluctuates, adaptive multiple bandpass filters are proposed to adaptively suppress the main harmonic current, which never influences the dynamic performance. In addition, the virtual impedance is connected in parallel with the bus capacitor to reduce the bus voltage overshoot. The key parameters design of the proposed control strategy is given and the dynamic response of the proposed control strategy is also discussed. Finally, a prototype of 900 W was fabricated and tested.
TL;DR: In this paper , a double cell management unit (DCMU) was proposed to perform Electrochemical Impedance Spectroscopy (EIS) on either single lithium-ion cells or modules formed by the series of two cells.
Abstract: A compact electronic circuit capable of performing Electrochemical Impedance Spectroscopy (EIS) on either single Lithium-ion cells or modules formed by the series of two cells is presented. The proposed device, named Double Cell Management Unit (DCMU), constitutes an important improvement to a recently proposed cell management unit, which combined EIS acquisition functions with a multichannel sensor interface compatible with thermistors, strain-gauges and moisture detectors. The proposed circuit maintains the versatility of the previous version and significantly extends the EIS frequency range, allowing vector impedance measurements from 0.1 Hz to about 15 kHz. The capability of handling both single Lithium-ion cells or series of two cells is obtained by adding a few external components to the previous version. This also allowed increasing the stimulation current to a maximum amplitude of 200 mA, resulting in improved resolution. Experiments consisting in EIS acquisition performed on batteries of different capacity at different temperatures and states of charge are described. Estimated impedance resolution (standard deviation) is 20 μΩ obtained at 1 kHz with a stimulation current of 100 mA amplitude.
TL;DR: In this article , the authors proposed to use well-established electrical circuit representations for hydraulic systems using expansion chamber configurations as the hydraulic suppressors, and then select the most suitable electrical representation through the experimental measurements of the IL.
Abstract: Currently, the acoustical performance of hydraulic noise attenuators is usually measured in terms of insertion loss (IL) and transmission loss (TL). Compared with the TL, experimental measurements of IL appear to be easier, however, the acquisition of source and load impedance for theoretical IL seems to be time-consuming and costly. Considering that the analogy between electrical system variables and fluidic ones is complete, well-established electrical circuit representations could be used for hydraulic systems using expansion chamber configurations as the hydraulic suppressors. Utilizing the Thevenin theorem and Norton theorem in the electrical network theory, two types of pressure oscillation source representations are equivalent insofar as the suppressors are concerned and then the expression for IL could be simplified. Finally, through the experimental measurements of the IL, the most suitable electrical representation would be selected. By implementing this method, the measurements of source impedance and load impedance tend to be avoided, which appears to be an attractive approach.
TL;DR: In this article , a series and parallel impedance shaping method is proposed to ensure that the output impedance of a filtered grid-connected inverter is dissipative up to the Nyquist frequency, where the inverter output impedance can be decomposed into two passive elements and one active element, its non-dissipative property results from the latter.
Abstract: The passivity theory provides an effective way to tackle the instability due to the inverter-grid interaction, which tells that the system stability can be guaranteed if the grid impedance and the inverter output impedance are both passive. Since the grid impedance is generally passive, the system stability can be immune to the grid impedance variation if the inverter output impedance is also passive. This paper develops a series and parallel impedance shaping method to ensure that the output impedance of the LCL -filtered grid-connected inverter is dissipative up to the Nyquist frequency. Since the inverter output impedance can be decomposed into two passive elements and one active element, its non-dissipative property results from the latter, and thus the virtual series impedance shaping is introduced to cancel out the active element. Unfortunately, it poses impact on the low-frequency loop gain and system phase margin in the meantime. To alleviate this impact, a high-pass filter is inserted in the series impedance shaping function. Subsequently, a virtual parallel impedance is introduced to enhance the passivity robustness, such as against filter parameter variations. Moreover, the proposed method does not require any additional sensors. Experiments from a 6-kW prototype confirm the effectiveness of the proposed method.
TL;DR: In this paper , a voltage-mode first-order all-pass network is proposed by using only four p-channel metaloxide-semiconductor transistors, one resistor and one capacitor.
Abstract: In this paper, a new voltage-mode first-order all-pass network is introduced. It is realized by using only four p-channel metal–oxide–semiconductor transistors, one resistor and one capacitor. The proposed filter enjoys the feature of high input impedance and does not require any additional current source. It is also free from any kind of passive element matching constraint. In order to test the workability of the proposed structure, a second-order all-pass network and quadrature oscillator are presented. Personal simulation program with integrated circuit emphasis using 0.18 µm, level-7 complementary metal-oxide-semiconductor process parameters with ± 0.9 V supply voltages are used to validate the performance of the proposed structure.
TL;DR: In this article , an improved current droop control strategy is proposed to increase the current distribution accuracy of the system and restrain the system frequency fluctuation on the basis of reducing the control operation complexity.