Impedance Network Research Articles

Analysis and Suppression of High-Frequency Resonance for Offshore Wind Power Grid-Connected Converter Considering Cable Capacitance Effect

Large-scale offshore wind farms have become the development trend in wind power generation. Long submarine cables are used to collect electrical energy in the collection networks of offshore wind farms. However, the distributed capacitance of cables cannot be ignored, which makes the impedance of the collection network complex and changeable. It is common to encounter high-frequency harmonic resonance (HFHR) problems when cables interact with wind turbine generators (WTGs). The HFHR may threaten the safe and stable operation of wind turbines. In order to solve this problem, firstly, the impedance of a collection network was constructed. Furthermore, the wind farm collection network was divided into the equivalent wind turbine subsystem (EWTS) and the remaining equivalent wind farm subsystem (REWFS). Then, the mechanism of HFHR was revealed based on the impedance stability analysis method. The effects of cable parameters, the number of connected WTG, and the grid impedance on the HFHR of the interconnected system were also analyzed. Finally, the hybrid damping control method, combining active damping control (ADC) and passive damping control (PDC), was proposed to suppress the resonance. A simulation and experiment were performed to verify the effectiveness of the analysis results and proposed control method.

A Hybrid Impedance Matching Network for Underwater Acoustic Transducers

The underwater acoustic transducer (UAT) is an electro-acoustic conversion device, which is a nonlinear reactive load. An impedance matching network is usually added between the power amplifier and the UAT. This paper proposes a hybrid impedance matching network (HIMN) combining passive impedance matching and active impedance matching. Compared with the conventional matching, this method can improve the matching frequency range and reduce matching delay. Firstly, the impedance model of the UAT is proposed, and the matching principle of the HIMN is analyzed. On this basis, the parameter design method is given within the required frequency range. Then, to reduce the matching delay of the system, a control method based on reference signal synchronization is proposed, including the reference compensation voltage calculation method and model prediction control (MPC) with two-step prediction. Finally, the simulation and experimental hardware in loop (HIL) results are given, which verify the effectiveness of the proposed HIMN and control algorithm proposed in this paper. The results show that the proposed HIMN can achieve a wider matching frequency range and shorter matching delay.

Frequency Band Broadening of Piezoelectric Ultrasonic Transducer Using Multifrequency Impedance Network Coupling Method

This paper addresses the bandwidth problem of ultrasonic transducers, and a frequency band broadening technique based on multi-frequency impedance network coupling is proposed. Based on the extended BVD circuit model, three coupled circuits including one first-order and two second-order are designed. The inductor-capacitor value and series-parallel connection method are reasonably chosen for tuning to achieve multi-peak resonance to improve the operating bandwidth of the transducer. The results show that for each order increase of the LC circuit, the resonance peak will increase by one, and the bandwidth will be broadened accordingly. Finally, the bandwidth of the first-order coupling circuit is increased by 50.45% and the bandwidth of the second-order coupling circuit is increased by 88.29%.

Three-Leg Quasi-Z-Source Inverter with Input Ripple Suppression for Renewable Energy Application

Single-phase inverters are widely employed in renewable energy applications. However, their inherent 2ω-ripple power can substantially affect system performance, leading to fluctuations in the maximum power points (MPP) of photovoltaic (PV) systems and shortening the lifespans of fuel cell (FC) systems. To alleviate input ripple, a three-leg quasi-Z-source inverter (QZSI) and its associated control strategy are proposed. The QZSI consists of a quasi-Z-source network, an H-Bridge inverter, and an active power filter (APF). The active filtering structure comprises filtering capacitors and the third bridge leg. The proposed control strategy consists of three loops: open-loop simple boost control, output voltage control, and 2ω-ripple suppression control. Open-loop simple boost control is utilized for shoot-through state modulation, output voltage control is applied to the two bridge-legs of the H-Bridge, and the additional third bridge-leg adopts a quasi-PR control (QPR) method that injects specific frequency harmonic voltage and suppresses newly generated low-frequency components of the input current. This method effectively avoids the drawbacks of utilizing passive filtering strategies, such as high-value impedance networks, low power density, and weak system stability. A simulation platform of 300W 144VDC/110VAC50Hz is constructed. The simulation results indicate that the addition of the third bridge leg under full load conditions reduces the input-side inductor current ripple ΔI from 1.89 A with passive filtering to 0.513 A, representing a reduction of 72.86%. The second harmonic ripple of the input current is reduced from 18.2% to 4.5%, and the fourth harmonic ripple is reduced from 16.5% to 2.1%. The DC bus voltage ripple ΔVPN falls from 70.75 V to 6.54 V, representing a reduction of 90.76%. The Total Harmonic Distortion (THD) of the output voltage and current are both less than 1%. The simulation results validated the feasibility of the proposed approach.

Hydrogen based configurations for an overhead crane with quasi-Z-source inverter

Most of the overhead cranes used to date are powered by diesel engine or electrical grid and voltage source inverter. The economic and environmental costs of fossil fuels, and the unsteady price of electricity, encourage exploring new applications for developing electric power technologies. In this scenario, the main objective of this paper is to analyze the technical and economic feasibility of two new configurations based on hydrogen system and quasi-Z-source inverter (qZSI) for an overhead crane. The first configuration uses a fuel cell (FC) connected to a qZSI to supply the crane. The second one integrates an electrolyzer (LZ) as an energy storage system (ESS) into the impedance network of the qZSI (without additional DC/DC converter), which allows to recover energy during the regenerative braking of the crane and use it to produce hydrogen. The modelling and control are described, and short simulations of the working cycle of the crane under different initial hydrogen tank levels, and long simulations with several working cycles, are considered. The results show the technical viability of the two hydrogen-based configurations and the control systems implemented, since they can power the crane under all the situations studied. Nevertheless, the configuration with FC and LZ presents a higher energy efficiency (65% vs 44% with the FC-only configuration). Regarding the economic study, both configurations are compared with a diesel-based and with a full-electric configuration powered by the grid. Analyzing both hydrogen-based configurations, the results show that the configuration with FC and FZ becomes more profitable after 1.56 years, despite the higher initial cost. However, both configurations result more expensive than those based on diesel engine and fully powered by the grid. The two proposed configurations would be more cost-effective than the initial configuration in a plausible future with a 40% decrease in hydrogen cost.

Space Robot On-Orbit Operation of Insertion and Extraction Impedance Control Based on Adaptive Neural Network

The on-orbit operation of insertion and extraction of space robots is a technology essential to the assembly and maintenance in orbit, satellite fuel filling, failed satellite recovery, especially modular in-orbit assembly of micro-spacecraft. Therefore, the force/posture impedance control for the on-orbit operation of insertion and extraction is studied. Firstly, the dynamic model of space robots’ system in the form of uncontrolled carrier position and controlled attitude is derived by using the momentum conservation principle. Through the kinematic constraints of the replacement component plug, the Jacobi relationship of the plug motion in the base coordinate system is established. Secondly, to achieve the output force control of the plug during the on-orbit operation of insertion and extraction, a second-order linear impedance model is established based on the dynamic relationship between the plug posture and its output force and the impedance control principle. Then, in order to improve the stability, robustness, and adaptability of the controller, an adaptive Radial Basis Function Neural Network (RBFNN) is used to approximate the uncertainties in the dynamic model for the force/posture control of the plug. Finally, the stability of the system is verified by the Lyapunov principle. The simulation results show that the designed neural network impedance control strategy can achieve a control accuracy of less than 10−3 rad for the plug’s attitude tracking error, less than 10−3 m for its position tracking error, and less than 0.5 N for its output force tracking error.

Electrical characteristics of the 3 × 6 × n cobweb cascaded LC complex impedance network

For the cobweb circuit network, the previous research focuses on the single-stage cobweb. In this paper, we studied a kind of multi-stage cobweb composed of n single-stage cobwebs, namely a 3 × 6 × n cobweb cascade LC network (CCLCN). To calculate the equivalent impedance of such large-scale complex circuit networks, we used a method that combines the replacement method with the modified recursive-transformation method (referred to as the R-MRT method). The CCLCN circuit was first replaced by a purely resistive circuit with identical connections, then the purely resistive circuit was calculated by the modified recursive-transformation method, and finally, the equivalent impedance of the CCLCN circuit was obtained by parameter replacement. Utilizing the above method, we obtained the exact analytical expression of the equivalent impedance of the 3 × 6 × n CCLCN. This result shows that the equivalent impedance problem of large-scale complex circuit networks such as the multi-stage cobweb has been solved.

Cascading failures modeling of electronic circuits with degradation using impedance network

Cascading failures modeling of electronic circuits with degradation using impedance network

Polarization-Resolved THz Imaging With Orthogonal Heterostructure Backward Diode Detectors

A fully integrated lens-coupled dual-polarization detector for imaging was designed, fabricated, and characterized in the terahertz (THz) region. Two zero-bias heterostructure backward diodes (HBDs) were monolithically integrated into a planar dual-polarization annular-slot antenna. An impedance matching network consisting of an interdigitated DC block and shorted stubs was implemented for maximum power transfer. The fabricated chip was then mounted on an extended hemispherical silicon lens for high antenna efficiency. The performance of the integrated detector has been characterized at 200 GHz. The detector module can simultaneously measure the two orthogonal linear polarized components of the incident THz waves, and hence obtain the polarization direction. On the basis of this polarimetric detection, polarization-resolved imaging of a Gaussian beam, as well as birefringent samples, was performed using the integrated detectors. The angular resolution of the polarization detection has been demonstrated to be as small as 3°. The single-pixel detector demonstrated here is amenable to array applications for THz focal-plane arrays that will have a significant impact on a wide range of remote sensing, though-barrier imaging, and detection/identification applications.

A Lightweight and Robust Drone MHz WPT System via Novel Coil Design and Impedance Matching

This paper proposes a comprehensive approach to address the challenges posed by the simultaneously varying dc load and coil coupling in drone wireless charging, which inevitably occur during battery charging and landing positioning. The combination of two new coil designs, a quasi-elliptic transmitting (Tx) coil and a “belt” receiving (Rx) coil, enables adequate power transfer at megahertz (e.g., 6.78 MHz) and over a large circular landing area. The on-board “belt” Rx coil (5.8 g) especially helps achieve lightweight and minimize air resistance. A load-pull-based impedance analysis is then performed to clarify the need for an impedance matching network (IMN) on both Rx and Tx sides (i.e., Rx-IMN and Tx-IMN). A new Rx-IMN explicit design is specially developed to significantly limit the range of variation in the coupling coil input impedance, thereby helping to simplify the design of the Tx-IMN to ensure an efficient power amplifier operation. With the proposed coil and IMN designs, actual drone wireless charging experiments demonstrated improved system dc-dc efficiency (max. 83.5%) and dc-dc voltage ratio stability at three representative landing positions (i.e., minimum, medium, and maximum coil coupling).

Harmonic Resonance Suppression With Inductive Power Filtering Method: Case Study of Large- Scale Photovoltaic Plant in China

Taking actual engineering as a case study, this article provides a novel scheme of applying the inductive power filtering method (IPFM) to resolve the harmonic resonance issues in large-scale photovoltaic (PV) plant. By using IPFM's special structure and dual zero-impedance design, the impedance network of large-scale PV plant is reshaped while the performance of power filters is improved, so that the harmonic resonance due to the interaction between the inverters and the power grid is suppressed. First, the topology and components of the IPFM-based large-scale PV plant are introduced. The three-phase mathematical model in harmonic domain is then established. Based on the deduced transfer matrix, the simplified circuit of the studied large-scale PV plant is obtain-ed. Moreover, the IPFM's resonance damping mechanisms on resonant frequency shift and harmonic amplification mitigation are analyzed. Both simulation and engineering tests verify the feasibility of the proposal.

Simulation and Analysis of Harmonic High Voltage Filters for Wind Farm

With the rapid development of the wind power industry, the total installed capacity of wind power has increased dramatically worldwide, and a large number of wind power installations need to be connected to the grid. In wind turbines, voltage flicker due to output power fluctuations caused by wind speed changes, and the application of a Voltage Source Converter (VSC) cause harmonic richness and other power quality problems to become more and more prominent. In this regard, the research is focused on the harmonic and reactive current distribution, impedance frequency characteristics, and voltage distortion rate of several offshore wind farm access systems, including the establishment of a harmonic current simulation model of the offshore wind farm delivery system, simulation analysis of network impedance frequency characteristics, simulation analysis of harmonic currents, and proposed a preferred filtering scheme. Taking into full consideration the characteristic harmonics of the wind farm, the system resonance generated by the submarine cable and the background harmonic level of the power grid, combined with the simulation results of the harmonic voltage, harmonic current, and network impedance frequency characteristics of each node, the technical solution of adding a direct-mounted high-voltage filtering device to the 220 kV bus at the metering station is proposed, which can destroy the system resonance conditions of the 3rd to 6th times of the submarine cable. Various wind farms and system operating conditions are able to form a stable harmonic absorption point to avoid the problem of harmonic amplification.

Frequency-phase-locking mechanism inside DC SQUIDs and the analytical expression of current-voltage characteristics

Direct-current superconducting quantum interference devices (dc SQUIDs) are ultra-sensitive flux-to-voltage convertors widely applied for biomagnetism and geophysics; they are a kind of magnetic-field-effect transistors (MFETs) with flux-modulated current-voltage characteristics. Compared to semiconductor FETs, dc SQUIDs still lack analytical expressions to interpret their inner formation mechanisms of the current-voltage characteristics. This article presents a frequency-phase-locking (FPL) model to derive the analytical expression of dc SQUIDs and reveal how the current-voltage characteristics are shaped by the circuit parameters between two Josephson junctions. The application of the analytical expression in the calculations of current-voltage characteristics is demonstrated; the results are compared with the numerical simulations. It is shown that a dc-SQUID is an FPL system inside and works as a current-modified nonlinear resistor in readout circuits; its current-voltage characteristics are the projections of three impedances of the network between Josephson currents. Those understandings enable electronic engineers to evaluate the design of dc-SQUID circuits directly through three network impedances extracted from the layout.

Noise‐Robust Optimization of Impedance Loading for Single‐RF MIMO Systems

Multiple‐Input‐Multiple‐Output (MIMO) systems are widely used to enhance the system capacity in wireless communications systems. The complexity and the cost for implementing the multiple radio frequency‐chain (RF‐chain) increases proportional to the number of signal streams. Therefore, so‐called load modulating single‐RF MIMO system is one promising technology in the practical aspects. Load modulating single‐RF MIMO can utilize two‐port network for controlling the load and the desired signal can be generate by loading proper set of impedance. In this paper, the optimization method for choosing the two‐port network impedance solution that is robust to the impedance noise is proposed and the simulations are conducted to verify the robustness. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Group-Connected Impedance Network of RIS-Assisted Rate-Splitting Multiple Access in MU-MIMO Wireless Communication Systems.

The reconfigurable intelligent surface (RIS) and rate-splitting multiple access (RSMA) are considered as promising technologies for the beyond Fifth-Generation (B5G) and Sixth-Generation (6G) wireless systems by controlling the propagation environment, which attenuates the transmitted signal, and by managing the interference by splitting the user message into common and private messages. Because conventional RIS elements have each impedance connected to the ground, the sum-rate performance improvement of the RIS is limited. Therefore, the new RISs, which have impedance elements connected to each other, have been proposed recently. To be more adaptive to each channel, the optimization of the grouping of the RIS elements is required. Furthermore, since the solution of the optimal rate-splitting (RS) power-splitting ratio is complex, the value should be simply optimized to be more practical in the wireless system. In this paper, the grouping scheme of the RIS elements according to the user scheduling and the solution of the RS power-splitting ratio based on fractional programming (FP) are proposed. The simulation results showed that the proposed RIS-assisted RSMA system achieved a high sum-rate performance compared to the conventional RIS-assisted spatial-division multiple access (SDMA) system. Therefore, the proposed scheme can perform adaptively for the channel and has a flexible interference management. Furthermore, it can be a more suitable technique for B5G and 6G.

Wideband Series Harmonic Voltage Compensator Using Look-Ahead State Trajectory Prediction for Network Stability Enhancement and Condition Monitoring

A wideband series harmonic voltage compensator (WSHVC) with an operating bandwidth of 10 kHz for microgrids with a plurality of grid-connected inverters (GCIs) is proposed. It generates a voltage to compensate for high-frequency harmonic voltage at the point of common coupling (PCC), resulting in a virtually zero high-frequency impedance at the aggregate output of the GCIs and, thus improving system stability. The generation of the harmonic voltage is based on predicting the state trajectory of the WSHVC after a switching period per half-switching cycle to determine the moment at which the switches in the WSHVC change their states. The PCC impedance and the equivalent impedance of the GCI network are extracted by analyzing the system response after injecting the entire system with particle-swarm-optimization (PSO) optimized multisine power disturbances. Therefore, system stability is predicted. The condition of passive components in the WSHVC is also monitored by estimating their values with the sampled state variables. A 500 VA, 1 MHz, FPGA-controlled, GaN-based prototype is evaluated on a 6.5 kVA testbed that consists of three commercial GCIs, nonlinear load, and adjustable grid impedance. A comparative study of the system performance with and without the WSHVC is conducted. Experimental results are favorably compared with theoretical predictions.

PASSOS: Passive Approximation Through Sum-of-Squares Orthogonal Rational Functions

Signal and power integrity design in the time domain requires equivalent circuit models for interconnects and packages, whose descriptions may only be available as tabulated impedance or admittance parameters. Accurate models for these components should maintain their physical properties including causality, stability, and passivity. Sum-of-squares (SOS) polynomials, which are guaranteed to be non-negative, can be used to address the problem of generating passive scalar models, such as driving point impedances or admittances, based on an existing causal, stable, but nonpassive model. However, the poor conditioning of a monomial basis in SOS constraints prevents large-order modeling. In this article, we expand the SOS framework to reciprocal multiport admittance or impedance network parameters by introducing a methodology based on SOS matrices. In addition, orthogonalized rational functions are incorporated to solve the conditioning problem by embedding the denominator polynomial in the basis.

New combined impedance‐source network inverter with high gain performance in low shoot‐through and improved quality factors

SummaryIn this paper, a new combined impedance‐source network inverter (CISI) with high voltage gain in low duty cycle is presented. With common ground between the input source and the inverter bridge and a continuous input current, the proposed converter is a suitable choice for renewable energy applications. The duty cycle of the inverter switches is low, leading to a reduction in losses and improving the efficiency. Also, due to the small duty cycle, the modulation index can be increased, and as a result, the quality of output voltages and currents is greatly improved. The proposed circuit has no switch in the input impedance network, and the number of components is reasonable compared to other works. Another advantage of the proposed converter is the low voltage stress on its capacitors and diodes. The proposed circuit is designed and tested at 180 W. The experimental results and the calculated values are close to each other, verifying the accuracy of the analysis.

A Current Controller Gain Characterization of Weak Grid Coupled Solar Inverter Through Impedance Interaction Modeling

The interface inverters arbitrate the network impedance based on the source characteristics for efficient solar energy harvesting. The wide impedance arbitration capability of the interface inverter defines the wide operational integrity with the ac network. In the weak grid scenario, the uncompensated grid inductance beyond point of common coupling (PCC) offers the negative damping for power oscillations at the PCC tugs the system toward instability. In this article, the negative damping influence due to interactions between the system impedance (filter inductance and grid power injection resistance) and ac network impedance (grid inductance) on the inverter closed-loop controller is characterized by observing the natural phase deviations in real and imaginary axis. Through distinguished system’s natural response, a novel second-order system impedance model is derived, and proposed current controller gain characterization aiming to achieve positive damping to mitigate the PCC’s oscillations. Further tuning of the controller based on the natural response of the derived impedance model accomplishes the enhanced grid injected power quality. The efficacy of the derived system impedance model along with coherence of current controller gain is demonstrated on hardware for enhanced power quality under the stable operating region.

24–35 GHz Filtering LNA and Filtering Switch Using Compact Mixed Magnetic-Electric Coupling Circuit in 28-nm Bulk CMOS

This paper presents compact 24–35 GHz filtering low noise amplifier (LNA) and filtering switch in 28-nm CMOS technology. A compact mixed magnetic-electric coupling circuit is designed, where a transmission zero is introduced out of the passband due to the cancellation of the magnetic and electric couplings. By analyzing the impedance characteristics, this structure can be designed with the impedance conversion function to replace the widely used transformers in integrated circuit designs. It shows the advantages of easy control of coupling coefficient and out-of-band rejection. Then, an LNA employing the magnetic-electric coupling circuits as impedance matching networks is designed. Image rejection can be achieved without increasing the circuit area. Moreover, by loading transistors to this mixed magnetic-electric coupling circuit, the input impedance can be controlled by the parasitic components of the transistor. Subsequently, a filter passband can be switched on and off, realizing a very compact filtering single-pole single-throw (SPST) switch. The fabricated filtering LNA is measured with a 3-dB bandwidth of 24–35 GHz, a noise figure (NF) of 2.4-3.6 dB, a maximum gain of 22 dB, and suppression of better than 25 dBc below 18 GHz. The filtering switch shows a minimum on-state loss of 2.1 dB at 28.6 GHz with better than 12.9 dB rejection below 16 GHz and off-state isolation of higher than 19 dB.