Showing papers on "Electrical impedance published in 2015"
TL;DR: In this article, the authors present an overview of the virtual-impedance-based control strategies for voltage-source and current-source converters, and a number of practical examples are demonstrated to illustrate the feasibility of virtual impedances.
Abstract: The virtual impedance concept is increasingly used for the control of power electronic systems. Generally, the virtual impedance loop can either be embedded as an additional degree of freedom for active stabilization and disturbance rejection, or be employed as a command reference generator for the converters to provide ancillary services. This paper presents an overview of the virtual-impedance-based control strategies for voltage-source and current-source converters. The control output impedance shaping attained by the virtual impedances is generalized first using the impedance-based models. Different virtual impedances and their implementation issues are then discussed. A number of practical examples are demonstrated to illustrate the feasibility of virtual impedances. Emerging applications and future trends of virtual impedances in power electronic systems conclude this paper.
468 citations
TL;DR: In this paper, the authors show that spatiotemporal variations over a surface may greatly extend the degree of wave manipulation in metasurfaces, and break several of their constraints associated with symmetries.
Abstract: Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the subwavelength scale. Here we add a temporal gradient to the picture, showing that spatiotemporal variations over a surface may greatly extend the degree of wave manipulation in metasurfaces, and break several of their constraints associated with symmetries. As an example, we synthesize a nonreciprocal classical analog to electromagnetically induced transparency, opening a narrow window of one-way efficient transmission in an otherwise opaque surface. These properties pave the way to magnetic-free, planarized, nonreciprocal ultrathin surfaces for free-space isolation.
361 citations
TL;DR: In this paper, the authors focus on current limiting for voltage-controlled inverters during overloads caused by poor transient load sharing between inverters and synchronous generators in islanded microgrids.
Abstract: This paper focuses on current limiting for voltage-controlled inverters during overloads caused by poor transient load sharing between inverters and synchronous generators in islanded microgrids The use of simple current reference saturation limiters can cause instability when the voltage regulator loses control after the current reference saturates The use of virtual impedance for current limiting is shown to improve transient stability during current limiting when operating in parallel with synchronous generators Small-signal analysis is used to set the virtual impedance magnitude and $X/R$ ratio, and validation is provided by simulation and experimental results
255 citations
TL;DR: The optimal design of the capacitor-current-feedback coefficient is presented and a phase-lag compensation for the loop gain is proposed in order to improve system stability for a resonance frequency of (fs/6).
Abstract: Capacitor-current-feedback active damping is an effective method to suppress the $LCL$ -filter resonance in grid-connected inverters. However, due to the variation of grid impedance, the $LCL$ -filter resonance frequency will vary in a wide range, which challenges the design of the capacitor-current-feedback coefficient. Moreover, if the resonance frequency is equal to one-sixth of the sampling frequency $(f_{s}/6)$ , the digitally controlled $LCL$ -type grid-connected inverter can be hardly stable no matter how much the capacitor-current-feedback coefficient is. In this paper, the optimal design of the capacitor-current-feedback coefficient is presented to deal with the wide-range variation of grid impedance. First, the gain margin requirements for system stability are derived under various resonance frequencies. By evaluating the effect of grid impedance on gain margins, an optimal capacitor-current-feedback coefficient is obtained. With this feedback coefficient, stable operations will be retained for all resonance frequencies except $f_{s} /6$ . Second, in order to improve system stability for a resonance frequency of $f_{s} /6$ , a phase-lag compensation for the loop gain is proposed. Finally, a 6-kW prototype is tested to verify the proposed design procedure.
245 citations
TL;DR: In this article, an electrochemical-based impedance matrix analysis for lithium-ion battery is developed to describe the impedance response of electrochemical impedance spectroscopy, and a method, based on EIS measurement, has been proposed to estimate the internal temperature of power lithium ion battery by analyzing the phase shift and magnitude of impedance at different ambient temperatures.
150 citations
TL;DR: In this article, the effect of dielectric properties of CFRP carbon rovings on eddy current measurement signal has been investigated and an explanation for that effect is seen in the measurement frequency and the capacitive structure of the carbon RoVings.
Abstract: Eddy current testing is well established for non-destructive testing of electrical conductive materials [1]. The development of radio frequency (RF) eddy current technology with frequency ranges up to 100 MHz made it possible to extend the classical fields of application even towards less conductive materials like CFRP [2] [3](Table 2). It turns out that RF eddy current technology on CFRP generates a growing number of valuable information for comprehensive material diagnostic. Both permittivity and conductivity of CFRP influence the complex impedance measured with RF eddy current devices. The electrical conductivity contains information about fiber texture like orientations, gaps or undulations in a multilayered material. The permittivity characterization influenced by dielectric properties allows the determination of local curing defects on CFRP e.g. hot spots, thermal impacts or polymer degradation. An explanation for that effect is seen in the measurement frequency range and the capacitive structure of the carbon rovings. Using radio wave frequencies for testing, the effect of displacement currents cannot be neglected anymore. The capacitive structures formed by the carbon rovings is supposed to further strengthen the dielectric influences on eddy current measurement signal [3]. This report gives an overview of several realized applications and should be understood as a general introduction of CFRP testing by HF Radio Wave techniques.
137 citations
TL;DR: In this paper, a graphene sheet is used as a tuning part of the high-impedance surface (HIS) that acts as the ground plane of a two-dimensional leaky-wave antenna.
Abstract: The concept of graphene-based two-dimensional leaky-wave antenna (LWA), allowing both frequency tuning and beam steering in the terahertz band, is proposed in this paper. In its design, a graphene sheet is used as a tuning part of the high-impedance surface (HIS) that acts as the ground plane of such 2-D LWA. It is shown that, by adjusting the graphene conductivity, the reflection phase of the HIS can be altered effectively, thus controlling the resonant frequency of the 2-D LWA over a broad band. In addition, a flexible adjustment of its pointing direction can be achieved over a wide range, while keeping the operating frequency fixed. Transmission-line methods are used to accurately predict the antenna reconfigurable characteristics, which are further verified by means of commercial full-wave analysis tools.
132 citations
TL;DR: In this paper, an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product was proposed, by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a λ/2 transformer.
Abstract: We present an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product. We achieve this by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a λ/2 transformer. Our theoretical model predicts an extremely flat gain profile with a bandwidth enhancement proportional to the square root of amplitude gain. We experimentally demonstrate a nearly flat 20 dB gain over a 640 MHz band, along with a mean 1-dB compression point of −110 dBm and near quantum-limited noise. The results are in a good agreement with our theoretical model.
130 citations
TL;DR: In this paper, a planar scalar impedance holographic metasurface is designed at a dominant TM surface wave mode frequency, which is capable of beam forming with a desired electric field polarization and high gain.
Abstract: This paper presents the design of a novel planar scalar impedance holographic metasurface, which is capable of beam forming with a desired electric field polarization and high gain. It is demonstrated that the surface can be constructed with patches of simple geometry and design. A detailed analysis of the mechanism of scalar impedance holographic metasurfaces is discussed. The scalar impedance holographic metasurface is designed at a dominant TM surface wave mode frequency. It is observed that the TM surface wave mode has an impurity of TE polarized electric fields of small magnitude. The presence of this impurity is exploited to design a holographic metasurface for beam forming with a desired polarization. This modified-HAIS is capable of forming a beam at a nonphase crossover frequency, unlike the conventional HAIS. The design procedure of the surface, with simulation and measurement results, is presented.
126 citations
11 Mar 2015-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a generalized theoretical approach for beam coupling impedances and stretched-wire measurements is introduced, and the dependence of the obtained beam impedance on the relativistic velocity β is investigated and found as material property dependent.
Abstract: First, a generalized theoretical approach towards beam coupling impedances and stretched-wire measurements is introduced. Applied to a circular symmetric setup, this approach allows to compare beam and wire impedances. The conversion formulas for TEM scattering parameters from measurements to impedances are thoroughly analyzed and compared to the analytical beam impedance solution. A proof of validity for the distributed impedance formula is given. The interaction of the beam or the TEM wave with dispersive material such as ferrite is discussed. The dependence of the obtained beam impedance on the relativistic velocity β is investigated and found as material property dependent. Second, numerical simulations of wakefields and scattering parameters are compared. The applicability of scattering parameter conversion formulas for finite device length is investigated. Laboratory measurement results for a circularly symmetric test setup, i.e. a ferrite ring, are shown and compared to analytic and numeric models. The optimization of the measurement process and error reduction strategies are discussed.
119 citations
TL;DR: In this article, the authors proposed a stability criterion for three-phase AC distributed power system (DPS) composed of an LC filter and a three phase boost rectifier, which cover the source output impedance and the load input admittance.
Abstract: This paper presents a stability criterion for three-phase AC distributed power system (DPS). While the source output impedance and the load input admittance under synchronous reference frame are generally investigated to predict the stability of the three-phase AC DPS, the infinity-norms of the impedance and admittance are innovatively adopted in the proposed criterion to improve the computational complexity and the conservatism. Meanwhile, the computational complexity and the conservatism of the proposed criterion are analyzed and compared with existing ones. Furthermore, the terminal characteristics of the studied three-phase AC DPS composed of an LC filter and a three-phase boost rectifier, which cover the source output impedance and the load input admittance, are comprehensively modeled. Finally, the effectiveness of the proposed criterion is validated by experimental results.
TL;DR: The electrical properties of Ni0.27Cu0.10Zn0.63Fe2O4 (NCZF) prepared from auto combustion synthesis of ferrite powders have been studied by impedance and modulus spectroscopy as mentioned in this paper.
Abstract: The electrical properties of Ni0.27Cu0.10Zn0.63Fe2O4 (NCZF) prepared from auto combustion synthesis of ferrite powders have been studied by impedance and modulus spectroscopy. We studied frequency and temperature dependencies of impedance and electric modulus of NCZF in a wide frequency range (20 Hz-5 MHz) at different measuring temperatures SM T (30-225 ℃). The complex impedance spectra clearly showed both grain and grain boundary effects on the electrical properties. The observed impedance spectra indicated that the magnitude of grain boundary resistance gb R becomes more prominent compared to grain resistance b R at room temperature, and with the increase in SM T , gb R decreases faster than the intrinsic b R. The frequency response of the imaginary part of impedance showed relaxation behavior at every SM T , and the relaxation frequency variation with SM T appeared to be of Arrhenius nature and the activation energy has been estimated to be 0.37 eV. A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicated that a non-Debye type of conductivity relaxation characterizes this material.
TL;DR: In this article, an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product is presented, which is achieved by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a $\lambda/2$ transformer.
Abstract: We present an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product. We achieve this by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a $\lambda/2$ transformer. Our theoretical model predicts an extremely flat gain profile with a bandwidth enhancement proportional to the square root of amplitude gain. We experimentally demonstrate a nearly flat 20 dB gain over a 640 MHz band, along with a mean 1-dB compression point of -110 dBm and near quantum-limited noise. The results are in good agreement with our theoretical model.
TL;DR: In this article, the authors proposed a method based on the simplified refined instrumental variable for continuous-time fractional systems method (Srivcf) combined with gradient-based optimisation to estimate the order of the fractional term in the ECM.
TL;DR: A method of estimating battery- cell core and surface temperature using a thermal model coupled with electrical impedance measurement, rather than using direct surface temperature measurements, is presented, which is advantageous over previous methods of estimating temperature from impedance.
Abstract: This study presents a method of estimating battery- cell core and surface temperature using a thermal model coupled with electrical impedance measurement, rather than using direct surface temperature measurements. This is advantageous over previous methods of estimating temperature from impedance, which only estimate the average internal temperature. The performance of the method is demonstrated experimentally on a 2.3-Ah lithium-ion iron phosphate cell fitted with surface and core thermocouples for validation. An extended Kalman filter (EKF), consisting of a reduced-order thermal model coupled with current, voltage, and impedance measurements, is shown to accurately predict core and surface temperatures for a current excitation profile based on a vehicle drive cycle. A dual-extended Kalman filter (DEKF) based on the same thermal model and impedance measurement input is capable of estimating the convection coefficient at the cell surface when the latter is unknown. The performance of the DEKF using impedance as the measurement input is comparable to an equivalent dual Kalman filter (DKF) using a conventional surface temperature sensor as measurement input.
TL;DR: In this paper, the authors developed dc impedance models for the rectifier and inverter stations for a VSC-HVDC system when they are viewed from a dc terminal.
Abstract: Resonances can have a negative impact on a voltage-source converter–high voltage dc (VSC–HVDC) system. This paper develops dc impedance models for the rectifier and inverter stations for a VSC-HVDC system when they are viewed from a dc terminal. The impedance models take converter controllers into account. The derived impedance models are validated by comparing frequency responses of the analytical model and the impedance measured at the dc terminal from a detailed VSC–HVDC model simulated in a real-time digital simulator. Resonances are examined in the frequency domain (e.g., Bode plots and Nyquist plots) using the derived analytical impedance models. The analysis is verified by time-domain simulations. Real-time digital simulation in RT-Lab demonstrates that the dc capacitor has a significant impact on resonances while the power transfer level has an insignificant impact on resonances.
TL;DR: A hybrid systems framework is used to develop an entire family of controllers that have Impedance Control and Admittance Control at two ends of its spectrum; and intermediate controllers that has stability and performance characteristics that are an interpolation of those of Impedances Control and admissance Control.
Abstract: Impedance Control and Admittance Control are two distinct implementations of the same control goal but their stability and performance characteristics are complementary. Impedance Control is better suited for dynamic interaction with stiff environments and Admittance Control is better suited for interaction with soft environments or operation in free space. In this paper, we use a hybrid systems framework to develop an entire family of controllers that have Impedance Control and Admittance Control at two ends of its spectrum; and intermediate controllers that have stability and performance characteristics that are an interpolation of those of Impedance Control and Admittance Control. The hybrid systems framework provides the scope for maintaining stability and achieving the best performance by choosing a specific controller for a given environment and by continuously changing the controller to adapt to a changing environment. The advantage of our approach is demonstrated with an extensive case study of a one-dimensional system and through experiments with the joint of a lightweight robotic arm.
TL;DR: In this article, the authors combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies.
Abstract: Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.
TL;DR: This paper presents an effective control scheme in dc microgrids to precisely share the load current oscillatory and dc components among distributed generation (DG) units by assigning appropriate output impedance values and droop coefficients to each DG unit.
Abstract: This paper presents an effective control scheme in dc microgrids to precisely share the load current oscillatory and dc components among distributed generation (DG) units. The proposed control strategy includes current and voltage control blocks. The current control block consists of oscillatory and dc current-sharing units. The main idea of the proposed method is to share the load current oscillatory and dc components among the DG units based on their rated power, by assigning appropriate output impedance values and droop coefficients to each DG unit. The voltage control block is a multiloop voltage control unit employed to control the microgrid voltage. The detailed model of the proposed control architecture is established, and the system dynamics is analyzed. Since the synthesis of a local controller uses only information of the corresponding DG unit, the design procedure is totally decentralized. The performance and dynamic response of the proposed control scheme are verified through extensive simulation studies and experimental results.
TL;DR: This work presents a power- and area-efficient three-stage amplifier that is able to drive a large capacitive load and achieves an optimized tradeoff between the frequency and the Q-factor of the complex poles.
Abstract: This work presents a power- and area-efficient three-stage amplifier that is able to drive a large capacitive load. Removing the inner Miller capacitor and employing cascode Miller compensation in the outer compensation loop could extend the complex-pole frequency of a three-stage amplifier, but result in a high Q-factor. A local impedance attenuation block consisting of a series RC network is proposed to control the complex poles. This block attenuates the high-frequency resistance at the second-stage output and achieves an optimized tradeoff between the frequency and the Q-factor of the complex poles. As the low-frequency resistance remains unchanged, a high dc gain is maintained. Implemented in 0.13 $\mu$ m CMOS process, the proposed design occupies an area of 0.0032 mm 2 and consumes a quiescent current of 10.5 $\mu$ A. When driving a 560 pF capacitive load, it achieves a unity-gain frequency of 3.49 MHz, an average slew rate of 0.86 V/ $\mu$ s, and an average settling time of 0.9 $\mu$ s.
TL;DR: In this paper, an analytical Mason equivalent circuit is derived for a circular, clamped plate piezoelectric micromachined ultrasonic transducer (pMUT) design in 31 mode, considering an arbitrary electrode configuration at any axisymmetric vibration mode.
Abstract: An analytical Mason equivalent circuit is derived for a circular, clamped plate piezoelectric micromachined ultrasonic transducer (pMUT) design in 31 mode, considering an arbitrary electrode configuration at any axisymmetric vibration mode. The explicit definition of lumped parameters based entirely on geometry, material properties, and defined constants enables straightforward and wide-ranging model implementation for future pMUT design and optimization. Beyond pMUTs, the acoustic impedance model is developed for universal application to any clamped, circular plate system, and operating regimes including relevant simplifications are identified via the wave number-radius product ka. For the single-electrode fundamental vibration mode case, sol-gel Pb(Zr0.52)Ti0.48O3 (PZT) pMUT cells are microfabricated with varying electrode size to confirm the derived circuit model with electrical impedance measurements. For the first time, experimental and finite element simulation results are successfully applied to validate extensive electrical, mechanical, and acoustic analytical modeling of a pMUT cell for wide-ranging applications including medical ultrasound, nondestructive testing, and range finding.
TL;DR: In this paper, a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film is presented, which is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent.
Abstract: We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Qi > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.
TL;DR: In this paper, a frequency-agile filtering power divider with constant absolute bandwidth and high selectivity is presented, which utilizes four coupled resonators to obtain the two functions of power division and filtering.
Abstract: This paper presents a novel frequency-agile filtering power divider with constant absolute bandwidth and high selectivity. The proposed design utilizes four coupled resonators to obtain the two functions of power division and filtering. Synthesis of the filtering power divider is carried out and the design guidelines are given. Varactors are then loaded to the resonators to enable frequency tuning. By using capacitors as well as magnetic and electric coupling to obtain required external quality factors and coupling coefficients, a constant absolute bandwidth is maintained when tuning the frequency. To demonstrate the validity of the proposed design, a circuit was fabricated. Experimental results show that the operating frequency can be changed from 0.62 to 0.85 GHz with the 3-dB absolute bandwidth of 60 $\pm$ 2.5 MHz. Moreover, transmission zeros are generated near the passband, resulting in high selectivity for each tuning state. Comparisons between the measured and simulated results are presented and good agreement is observed.
TL;DR: In this article, a commercial high-power graphite anode was analyzed by the distribution of relaxation times (DRT-method), enabling a separation of loss processes by their individual time constants.
TL;DR: In this paper, a noninvasive method for calculating utility harmonic impedance at the point of common coupling (PCC) is proposed based on a statistical signal processing technique, known as independent component analysis (ICA).
Abstract: This paper presents a new noninvasive method for calculating utility harmonic impedance at the point of common coupling (PCC). The proposed method is based on a statistical signal-processing technique, known as independent component analysis (ICA). The complex ICA technique is applied to the equations derived from Northon equivalent circuit model at the PCC in order to estimate the utility harmonic current values. Then, the estimated values of the utility harmonic current are used in an optimization problem to calculate the utility harmonic impedance. Due to considering the utility harmonic current variations in utility harmonic impedance calculation, the proposed method is relatively robust against the background harmonic fluctuations. The results obtained from computer simulation and a real case study verify the effectiveness of the proposed method.
TL;DR: In this paper, the stored energy of an antenna is defined from the difference between the energy density and the far field energy for many but not all cases, and the results indicate that stored energy in the fields, currents, and circuit models agree well for small antennas.
Abstract: Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted L-antennas, and bow-tie antennas. We use Brune synthesized circuit models to determine the stored energy from the input impedance. We also compare the results with differentiation of the input impedance and the obtained bandwidth. The results indicate that the stored energy in the fields, currents, and circuit models agree well for small antennas. For higher frequencies, the stored energy expressed in the currents agrees with the stored energy determined from Brune synthesized circuit models whereas the stored energy approximated by differentiation of input impedance gives a lower value for some cases. The corresponding results for the bandwidth suggest that the inverse proportionality between the fractional bandwidth and Q-factor depends on the threshold level of the reflection coefficient.
TL;DR: In this article, an embedded impedance-based piezoelectric sensor was fabricated by using mixture of cement powder and epoxy resin as packaging layer, and the effects of temperature and load on impedance and conductance spectra of the sensor were investigated.
TL;DR: In this article, an impedance model-based frequency domain analysis was employed to detect subsynchronous resonances (SSRs) in Type-3 wind farms with TCSC.
Abstract: This paper employs impedance model-based frequency domain analysis to detect subsynchronous resonances (SSRs) in Type-3 wind farms with thyristor-controlled series capacitor (TCSC). The contributions of this paper are 1)the derivation of dynamic phasor-based TCSC impedance model and 2)the application of such an impedance model in Type-3 wind energy systems for SSR analysis. Impedance models for TCSC with constant firing angle control and impedance control are derived in this paper. With the derived impedance models, Nyquist stability criterion is applied to compare SSR stability in Type-3 wind farm with TCSC or with fixed capacitor compensation. This paper employs analytical models to demonstrate TCSCs capability in avoiding SSR in Type-3 wind generator interconnection systems. The analytical results obtained through impedance models are validated by detail model-based (with thyristor switch-modeled) time-domain simulation in MATLAB/SimPowerSystems.
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19 May 2015TL;DR: In this paper, the system and methods for generating and using characteristics of an impedance matching model with different impedance matching networks are described, and the impedances and/or power efficiencies are measured using a network analyzer or a sensor.
Abstract: Systems and methods for generating and using characteristics of an impedance matching model with different impedance matching networks are described impedances and/or power efficiencies are measured using a network analyzer or a sensor. The impedances and/or power efficiencies are used to determine the characteristics. With use of different impedance matching networks, the values of the characteristics are changed to achieve same or similar results across different plasma tools for a variety of conditions.
TL;DR: In this paper, the authors presented a method for dc-side harmonic current calculation and dc-loop impedance calculation for an LCC-MMC hybrid HVDC transmission system with reverse current blocking diodes.
Abstract: For an LCC–MMC hybrid HVDC transmission system with reverse current blocking diodes, this paper presents a method for dc-side harmonic current calculation and dc-loop impedance calculation. First, in the calculation of dc-side harmonic currents, the line-commutated converter at the rectifier side is replaced by the three-pulse harmonic voltage sources; the modular multilevel converter is represented by an equivalent passive circuit based on the linearization theory; an improved calculating method for the coupled line model is introduced into calculating the admittance matrix of the dc transmission lines to improve the computational efficiency; and then this paper describes the complete procedures of the proposed method. Second, based on the dc-side equivalent models mentioned before and the nodal voltage analysis method, this paper presents an analytical method for the calculation of dc-loop impedance according to the definition of dc-loop impedance Finally, the PSCAD/EMTDC simulation verifications have been carried out based on a 1500 MW/ ${+} 500$ kV MMC-HVDC system, a 3000-MW/ ${\pm}$ 500-kV LCC–MMC hybrid HVDC system, and its dc network. The simulation results and the analytical results coincide with each other, and the effectiveness of the proposed methods is proved.