Circuit Parameter Variations Research Articles

Determination of magnetic coupling and its influence on the electromagnetic tube forming and discharge circuit parameters

The coil-workpiece magnetic coupling coefficient K is one of the factors that influence the efficiency of electromagnetic forming (EMF) process. Along with this, an evaluation of the magnetic coupling coefficient is important in simplifying the electrical representation of the process. The first aim of this study is to analyse the effect of K on the EMF process efficiency, and second is to obtain a simplified relation between K and coil-workpiece gap (h) and thereby study the variation of discharge circuit parameters with h.The analysis is carried out with the help of experiments, and the finite element based numerical simulation. Aluminum tube of 100 mm length and 1.5 mm thick is electromagnetically expanded using a 7 turn helical coil. Trials are taken for the different gaps between the coil and tube keeping the discharge energy constant. The coupling coefficient (K) variation with the coil-tube gap (h) is related with curve fitting, and this K-h relation is then used to analyze the discharge circuit parameter dependency on h. Simulation results, as well as K-h relation based analytical study, show a good match with the experimental observations. The EMF process efficiency and tube displacement are found to be improved exponentially with the increase in K. Among the discharge circuit parameters, with the increase in h, exponential rise in inductance and exponential decay in peak current is observed with a marginal decrease in the resistance.

Gain- and Loss-Induced Topological Insulating Phase in a Non-Hermitian Electrical Circuit

There have been considerable efforts devoted to the study of topological phases in certain non-Hermitian systems that possess real eigenfrequencies in the presence of gain and loss. However, it is challenging to experimentally realize such non-Hermitian topological insulators in either quantum or photonic systems, due to the difficulties in introducing controlled gain and loss. On the other hand, the wide choices of active circuit components provide us with unprecedented convenience and flexibility in engineering non-Hermitian topological insulators in electrical circuits. Here, we report experimental realization of a one-dimensional (1D) non-Hermitian topological circuit which exhibits topologically protected edge state purely induced by gain and loss. We show that by tuning the value of the positive/negative resistors in the circuit, our system can switch between different topological phase regions. The topological edge states and interface states are observed at the circuit edge and at the interface between a trivial and nontrivial circuit, which are manifested by a prominent impedance peak at the mid-gap frequency topologically robust to variations of circuit parameters. Our work opens a new gateway towards actively controllable topological systems.

A Back-Stepping Control Method for Modular Multilevel Converters

In this article, a back-stepping method (BSM) in a–b–c reference is presented to establish the stable operating conditions for modular multilevel converter (MMC). The designed BSM utilizes arm currents, sum of submodule capacitors voltages and MMC input energy as the main variables to form the energy functions. The proposed BSM is designed by well-known dynamic MMC equations to be applicable for both single- and three-phase ones while the control of variables is also guaranteed by BSM. A virtual control input containing input energy error and its dynamics is defined in the second energy function to further enhance the appropriate transient responses of the MMC. The proposed BSM has inherent feature of the circulating current suppression control loops which helps avoiding additional control loops. Moreover, several assessments are presented to show how BSM coefficients contribute to the noticeable decrement in control variables errors of the MMC system. Experimental and simulation results prove an excellent capability of BSM for controlling MMCs compared to the conventional PI linear controller. Moreover, the BSM robustness against the variations of the MMC circuit parameters is validated.

Study of complex dynamics in DC-DC boost converter with dSPACE-based real time controller

Switching converter circuits are nonlinear and time-varying in nature. In this paper, the complex dynamics in voltage mode controlled (VMC) DC-DC boost converter has been investigated through simulation and experimentation. The converter is controlled by naturally sampled constant frequency pulse width modulation (PWM) signals in continuous conduction mode (CCM) and converter exhibits fundamental, quasi-periodic and chaotic oscillations for the variation of circuit parameters. In simulation study, the model of boost converter is computed by non-autonomous differential equations and finally, the computational waveforms have been verified with experimental results. In order to verify simulation study, a laboratory scale prototype of closed-loop boost converter has been fabricated. The closed-loop converter is controlled by dSPACE in real-time platform. The results obtained from simulation and experimental study have been presented and compared. It has been observed that the route to chaos is achieved by the slow-scale instability in this proposed study.

Methods of Improving the Accuracy of Simulating Delays and Peak Currents of Combinational CMOS-Circuits at the Logical Design Level

With the reduction of the technological dimensions of transistors, the influence of the variations of circuit and technological parameters on the values of the delay of the elements of combinational CMOS-circuits has grown significantly. Due to the spread of the values of these parameters, the uncertainty of delays appears, which leads to the necessity to define the ranges of possible delay values. The peak current in power lines when switching the inputs of gates is another factor increasingly influencing the design process of CMOS circuits in the transition to nanometer technologies. The value of the peak current is used to estimate the voltage drop in the power lines, which in turn is necessary to calculate the width of the power lines of CMOS circuits and switch off the transistors in the method of reducing the static power. The methods of full circuit simulation do not comprehensively analyze the circuits with a large number of inputs and the methods at the logical level of designing CMOS circuits do not provide the desired accuracy of the evaluation of the values of the delays and the peak current in the circuit. The problem of increasing the accuracy and the reliability of the analysis of the performance and peak currents of CMOS combinational circuits, taking into account the simultaneous switching of the inputs, as well as the analysis of logical correlations of the signals, is considered. The proposed method is based on using the cubic approximation of the correction difference of delays, taking into account the simultaneous switching of inputs. It is shown that the developed techniques of the analysis of the performance and peak currents of CMOS combinational circuits improve the accuracy of the upper estimates of the analyzed parameters by up to 3% compared with accurate simulation and make it possible to reduce the pessimistic upper estimate by factors of 2 to 3 compared with the estimate of the worst case. The developed methods of improving the accuracy of simulating delays and peak currents of combinational CMOS-circuits can be used as an addition to the existing CADS tools for VLSI for noise-immunity analysis, the analysis of the peak currents, characterization of complex functional units, and improving the accuracy of classical static analysis. To improving the accuracy of the interval estimates of the minimum delays and maximum peak current, the simulation methods taking into account the simultaneous switching of the inputs of the logical element are developed. In relation to the circuit simulation, the error of these methods does not exceed 3%. Compared with the results obtained without taking the simultaneous switching into account, reducing the minimum delay by up to 50% and the pessimistic estimate of the peak current of combinational circuits is reduced on average by 50–55%.

Enhancing Q-Factor in a Biquadratic Bandpass Filter Implemented with Opamps

Active filter design is a mature topic that provides good solutions that can be implemented using discrete devices or integrated circuit technology. For instance, when the filter topologies are implemented using commercially available operational amplifiers (opamps), one can explore varying circuit parameters to tune the central frequency or enhance the quality (Q) factor. We show the addition of a feedback loop in the signal flow graph of a biquadratic filter topology, which enhances Q and highlights that a sensitivity analysis can be performed to identify which circuit elements influence central frequency, Q, or both. In this manner, we show the opamp-based implementation of a biquadratic bandpass filter, in which Q is enhanced through performing a sensitivity analysis for each circuit element. Equations for the central frequency and Q are provided to observe that there is not a direct parameter that enhances them, but we show that from sensitivity analysis one can identify the circuit elements that better enhance Q-factor.

Disturbance-Observer-Based DC-Bus Voltage Control for Ripple Mitigation and Improved Dynamic Response in Two-Stage Single-Phase Inverter System

Two-stage single-phase inverter system has found many applications in distributed generators and grid-connected systems. However, the existence of double-line frequency ripple on the dc-bus voltage due to single-phase inverter's operation has given rise to some design and reliability issues. Some of these are the degradation in the quality of inverter's output voltage and shortening of dc-bus capacitor's lifetime. The problem is rooted in the controller design of the front-end dc-dc converter, which is often designed based on a simplified mathematical model of the dc-dc converter that fails to account for some complex phenomena, such as system's nonlinearities and circuit parameter variations due to temperature and aging effects. In this paper, a disturbance-observer-based control is proposed where these unmodeled effects are treated in the form of lumped disturbance and compensated for in a feed-forward manner. The major advantage of this control solution is that only minimal plant information is needed for controller design and that a decoupled composite controller can be realized, where the feedback compensator is designed to meet certain stability criteria while the disturbance-observer-based feed-forward compensator is designed to handle fast transient events. A prototype of a dual-active-bridge (DAB) dc-dc converter implemented with disturbance-observer-based control is constructed to verify its effectiveness. Experimental results show that the dynamic response of the DAB converter is significantly improved and the double-line frequency ripple on the dc-bus voltage is effectively suppressed by the proposed control solution.

Transient and steady coexisting attractors in a new memristor-based 4-D chaotic circuit

In this study, a new current-controlled memristor is proposed and its characteristics are analyzed. Based on this new memristor, a new four-dimensional chaotic circuit is proposed. The complex dynamics of the proposed chaotic circuit are investigated. From the results of the theoretical analysis and the numerical simulations, it is found that the memristor-based chaotic circuit can generate different types of attractors including single-scroll, double-scroll, and periodic attractors for varying circuit parameters. By taking symmetrical initial conditions, symmetric steady coexisting attractors are obtained under the same set of circuit parameters. For certain initial conditions, striking transient coexisting attractors with different timescales can be obtained. In particular, there are two transient changes occurring successively at different time scales respect to the same initial conditions for the proposed chaotic circuit, which is a novel dynamic property. Finally, a practical circuit platform that describes the proposed chaotic circuit on Field Programmable Gate Arrays (FPGA) is designed, and some experimental results are presented for confirmation.

Modeling and Experimental Verification of High-Frequency Inductive Brushless Exciter for Electrically Excited Synchronous Machines

Electrically excited synchronous machines have shown potential to be an alternative to permanent magnet synchronous machines in electromobility and wind power applications. High-frequency wireless power transferring technology enables a compact design of brushless exciters for the machine. In this paper, a dynamic model of high-frequency brushless exciters is proposed for the purposes of operating condition monitoring and excitation control. The modeling is done by using arithmetic and differential equations as well as considering different operation modes of the system. The operation modes are defined based on the physical behaviors of the excitation circuit. Experiments are performed to verify the model with variations of different circuit parameters. Furthermore, parameter sensitivity study, component parameter selection, and loss analysis are conducted to demonstrate the effectiveness of the model. The model is therefore proposed as an effective tool to assist the design and optimization of the brushless excitation system.

A linear magnetic flux-to-voltage transfer function of a differential DC SQUID

A superconducting quantum interference device with differential output or ‘DSQUID’ was previously proposed for operation in the presence of large common-mode signals. The DSQUID is the differential connection of two identical SQUIDs. Here we show that besides suppression of electromagnetic interference this device provides effective linearization of the DC SQUID voltage response. In the frame of the resistive shunted junction model with zero capacitance, we demonstrate that spur-free dynamic range of the DSQUID magnetic flux-to-voltage transfer function is higher than 100 dB while the total harmonic distortion of a signal is less than 10−3% with a peak-to-peak amplitude of a signal being a quarter of half flux quantum, 2Φa = Φ0/8. Analysis of the DSQUID voltage response stability to a variation of circuit parameters shows that DSQUID implementation allows for highly linear magnetic flux-to-voltage transformation at the cost of a high identity of Josephson junctions and high-precision current supply.

Two-dimensional Transmission Line Modeling method: An algorithm considering non-homogeneous media and ionization

This work presents a two-dimensional Transmission Line Modeling (TLM-2D) method for modeling non-homogeneous media and non-linearities. The presented method is derived on top of the classical TLM-2D method with reactive and conductive stubs to modify the properties of the medium. Taking advantage of the analogy between electromagnetic and circuits theories, nonlinearities such as soil ionization, can be solved numerically through models formulated to represent electrical conductors, such as grounding systems. Using this analogy, the analysis can be extended more generically to non-homogenous and lossy media. Then, nonlinearity phenomena is included in the classical TLM-2D model through the dynamic variation of circuit parameters. This variation is obtained through the developed analytical based tests. Computational implementation details are also reported. A case study is presented considering a grounding grid mesh in non-homogeneous media submitted to lightning surges. Comparative test results with the state of the art highlight the improved precision of the presented solution.

Unified Discrete-Mapping Model and Dynamical Behavior Analysis of Current-Mode Controlled Single-Inductor Dual-Output DC–DC Converter

Buck type, boost type, and buck–boost type are basic topologies of single-inductor dual-output (SIDO) dc–dc converters. Current-mode controlled SIDO dc–dc converters have three current borders in wide-range parameter variations. According to the change of inductor current which presents five trends of “up–down–down,” “up–up–down,” “up–down–up,” “down–up–down,” and “up–down,” the corresponding current borders are defined. On this basis, a unified discrete-mapping model of five inductor current trends is established and the boundary equations of system stability and mode shifting are derived in the meantime. The dynamic behaviors with the variations of circuit parameters in different inductor current trends are analyzed in detail by numerical simulation, and theoretical analyses of period-doubling bifurcation and tangent bifurcation are presented to validate the simulation results. The research results indicate that the SIDO dc–dc converter has different bifurcation sequences with the same circuit parameter varying for different inductor current trends. Operating regions of the converter are given in this paper, which provides theoretical guidance in designing current-mode controlled SIDO dc–dc converters. The experimental results are presented to verify the correctness of theoretical analysis and unified discrete-mapping model.

Analysis of Variation in Circuit Parameters for Substitution of Weed Plant Tissue under Electric Impulse Action

To substantiate the quantitative values of the process of destruction of weeds by means of electric impulse and to elucidate the mechanism of damage and the sequence of disturbances that occur in the internal structure of the processed plants, it is necessary to know not only the design of the electrical circuit of the plant tissue substitution but also to have information on the nature of the change in the parameters of the elements of this scheme during electric damage. The presented technique allows (with the help of inexpensive and accessible technical means) to control the damage to the tissues of a weed plant and to calculate quantitative values using developed mathematical apparatus. The analysis shows that the damage to weed plant tissues can be characterized, first of all, by the loss of cell membranes in their semipermeable functions and an increase in the active conductivity of the processed areas of plants. Such changes in the internal structure of plant tissue lead to loss of cell viability in the areas subjected to the electric impulse treatment. The presented analysis fits the current thinking of biophysicists on the electrical damage to the internal structure of biological objects. The technological studies of the process of the electric impulse irreversible damage to plant tissues conducted, based on the analysis presented in the article, allow us to limit the supplied electric energy that makes it possible to make electric impulse weeding an energy-saving means of combating weeds.

Mating Sensitivity Analysis and Statistical Verification for Efficient Yield Estimation

Parametric yield is a significant threat to the reliability of nanoscale analog and mixed-signal circuits. A critical yet challenging problem of yield estimation is to account for multiple circuit performance. In this paper, we propose a novel nonparametric statistical verification methodology to efficiently estimate the parametric yield due to 65-nm technology for multiperformance constraints. Our proposed approach exploits the fact that circuit parameters variation has different impacts on the circuit performance. Hence, a global sensitivity analysis classifies the circuit parameters according to their influence on the desired circuit performances. Based on this classification, an efficient joint recurrence verification (JRV) algorithm, a procedure inspired from DNA analysis, is performed on the most “critical/influential” parameters. A global hypothesis testing procedure is then performed based on the computed JRV metrics. We demonstrate the effectiveness of our methodology on two benchmark circuits. The acquired results show the ability of our approach to handle multiple corners and multiple performances yield problems with up to $11 {\times }$ speedup compared to conventional techniques with an average error smaller than 3%.

Многополюсный контроллер нечеткой логики для усовершенствования управления шунтирующими реакторами

The article considers the problem of achieving more efficient operation of a multipole fuzzy logic controller (MFLC) intended to control the shunting reactor reactive power for stabilizing the voltage at the buses of high-voltage electric networks and for enhancing the operational reliability under the conditions of uncertain variations of power system circuit and operating parameters. A new algorithm for controlling the shunting reactor’s reactive power or inductive reactance depending on the load impedance, on the load variation rate, and voltage at the network buses is proposed. The results from a numerical experiment carried out by means of computer modeling confirm the efficiency of the proposed control algorithm for the MFLC with using the fuzzy logics theory.

A Dual Band Branch Line Coupler With Wide Frequency Ratio

A dual-band quadrature branch line coupler (BLC) with wide frequency ratio has been proposed in this paper. A dual-band quarter wave ( $\lambda $ /4) transmission line structure with wide frequency ratio operation has also been presented here with closed-form design equations. An analysis for the BLC’s circuit parameters variations versus frequency ratio in the view of the implementation has been carried out as well. In order to the experimental verification, a dual-band BLC has been designed, implemented, and analyzed then tested for long term evolution (LTE) 0.7GHz and public safety band (PSB) 4.9GHz. The novelty of the proposed design is the wide frequency ratio of its dual-band operation, which can reach up to 11.8.

A new dual band 4 × 4 butler matrix with dual band 3 dB quadrature branch line coupler and dual band 45° phase shifter

A new dual band 4 × 4 butler matrix (BM) without crossover has been proposed, implemented and analyzed in this paper. A new dual band 45° phase shifter has also been proposed. The dual band BM, dual band 3 dB quadrature branch line coupler (BLC) and dual band 45° phase shifter have been designed using Keysight Technologies’ Advanced Design System (ADS) software and implemented on the RO 5870, having a thickness of 0.787 mm for 1.0 GHz and 2.5 GHz operating frequencies. Before the implementation of the proposed BM, the dual band 3 dB quadrature BLC and dual band 45° phase shifter have been designed, implemented and analyzed. The proposed dual band 4 × 4 BM has been developed by placing four dual band 3 dB quadrature BLCs and two dual band 45° phase shifters at their appropriate positions. Circuit parameters variation of the proposed BLC, phase shifter and BM with frequency ratios have been studied in this paper. The measured and simulated results of the dual band BM validated the design methodology. A performance analysis comparing the proposed BM with the existing butler matrices has also been carried out.

Statistical estimation of delay in nano-scale CMOS circuits using Burr Distribution

the process of modern integrated circuit (IC) design has been challenged by many factors. One of the most important challenges is the variation of device and circuit parameters during the manufacturing process. In this paper, the effects of manufacturing process variations on the gate delay have been modeled and an accurate yet low-cost simulation method for estimation of the circuit performance has been proposed. This additive method takes advantage of a 3-parameter probability density function (PDF), known as Burr distribution, to estimate the delay of each gate on the critical path. In this work, it is demonstrated that our proposed method is more accurate than previously proposed methods by taking into account the skewness of delay PDF. Although our proposed method is based on a 3-parameter PDF, we demonstrate that the simulation cost of our proposed method is no more than the conventional 2-parameter Gaussian PDF. We have compared the accuracy of our proposed method against the HSPICE simulation results. Moreover, we have compared the accuracy of our method with the most recent works with a 2-parameter PDF. The results for ISCAS85 benchmark circuits in our work have shown for 99 percentile points with average errors of 3.62, 3.49 and 2.78% in 90 nm, 45 nm and 22 nm technologies respectively.

Direct-Lyapunov-Based Control Scheme for Voltage Regulation in a Three-Phase Islanded Microgrid with Renewable Energy Sources

In this paper, the local control structure of a microgrid is partially modified by a Lyapunov-based controller. This controller is derived based on direct Lyapunov stability theory (DLST) in order to calculate proper switching functions for the stable operation of the local controller as well as proper local performance of each inverter-based distributed generation (DG) unit. The main contribution is the use of DLST-based controller in a hierarchical primary control structure along with a DC-side voltage regulator. A current-based droop controller is also introduced along with a voltage harmonic compensation technique. The control limits of droop equations are calculated based on steady-state and dynamic capability curve as well as voltage-frequency ellipse curve. The effect of the variations of voltages and circuit parameters on the capability curves are also investigated and the microgrid (MG) steady-state operation area is obtained. In the proposed method, the DC-voltage variations are regulated by an additional voltage control loop based on a current reference correction signal. The above-mentioned approaches are derived thoroughly with mathematical equations. The effectiveness of the designed controllers is verified by a MATLAB/SIMULINK simulation platform (Matlab/Simulink R2014a, Mathworks, Inc.) with harmonically distorted intermittent loads. The results show the appropriate performance of the proposed controllers during both steady-state and transient dynamic conditions.

Phase Noise of Unsaturated Two-Stage Voltage-Controlled Ring Oscillator Without Tail Current

This paper investigates the phase noise (PN) of two-stage voltage-controlled ring oscillators. The delay cell is source-coupled pair with no tail current source, suitable for reduced voltage swing as supply reduces under technology scaling. With two stages, the output can become unsaturated, introducing extra cycle-to-cycle correlation and adding PN. The new cycle-to-cycle PN model is developed and applied to two different cell topologies. The design was fabricated in 1.2-V 0.13- $\mu \text{m}$ CMOS, operating at 0.89-GHz oscillator frequency with 200- $\mu \text{W}$ power consumption. PN measurement and simulation agree with theory over circuit parameter variations and corresponding design insights are drawn. Specifically as tuning voltage varies from 0.5 to 0.6 V, PN increases by around 5 dB.