Large-signal Model Research Articles

An Extensive Large Signal Equivalent Circuit Model of GaAs-PIN Photodiode

Based on the variation trend of the depletion layer of GaAs-PIN photodiode (PD) under different optical power and reverse bias voltages, an extensive large-signal equivalent circuit model that characterizes PD in non-punch-through and punch-through states is proposed in this article. According to the analysis of the PD’s depletion layer variation, the nonlinear parameters of the model are described by exponential function and Gaussian function. To verify the reliability of equivalent circuit model, on-chip measurements were performed on PIN-PD fabricated by commercial GaAs process, and the measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> and reflection coefficient agree with the proposed model simulation results well. Furthermore, using the proposed model for simulation with CAD tools shows that reducing junction capacitance has potential in improving PD output power and gain flatness. At the same time, the model provides a certain reference for selecting bias condition in the design of the PD matching network and fabricating PD with high power output.

Control of an Inductive Power Transfer System Using a Double Coil Structure

This paper presents the design of the control of the system using a double DD coil structure. The double DD coil is a layered coil structure that consists of two single DD coils, rotated to each other by 90°. A large-signal and small-signal model of the proposed IPT system are designed for control synthesis. The small-signal model is derived from the large-signal using harmonic approximation and the extended describing functions (EDF). For the small-signal model, voltage and current control schemes were proposed for the purpose of wireless battery charging. The robustness of the control is tested on a small-scale IPT system using double DD coils and resistive load. The results are evaluated at different reference voltages, currents, loads and coupling coefficients.

A Subspace Identification Technique for Real-Time Stability Assessment of Droop Based Microgrids

Real-time detection of the microgrid stability is crucial for determining and adjusting the power-sharing droop control's gains to maintain a sufficient stability margin. Maintaining minimum relative stability should be ensured at different operating conditions to accommodate sudden system changes. This article develops a novel subspace-based identification technique to assess microgrid stability in real-time without relying on offline analytical small or large-signal models. Unlike conventional system identification techniques that require the introduction of external excitation (signal probing, load switching, or contingency event), the proposed method employs a simple internal routine through small and short-duration perturbations in the active power droop gain of inverter-based distributed generation (IBDG). The use of subspace identification does not require pre-defining the system's order, avoids the exhaustive computations associated with iterative identification methods and can handle a change of microgrid's network configuration. The proposed stability assessment method has been tested on an IBDG microgrid considering different operating conditions in MATLAB/Simulink. The accuracy of the proposed real-time stability assessment tool is determined by comparing the results to the analytically-derived small-signal model as well as the Matrix pencil and Prony methods.

Constrained Predictive Control Based on a Large-Signal Model for a Three-Phase Inverter Connected to a Microgrid

Small-signal models are mostly used to model and design inverter-dominated microgrids. Conversely, this article proposes a large-signal model for grid-forming inverters connected to a microgrid based on the active and reactive power dynamic equations. In this work, it is proposed to use this nonlinear model to develop a constrained predictive control for the inverters connected to a microgrid. The main features of this proposed control are follows: first, direct voltage control (in amplitude and frequency) is not necessary; second, stability is guaranteed under a wide range of line impedances (hence, the virtual impedance is not needed); third, the proposed control can operate with unbalanced and nonlinear loads. Moreover, a theoretical stability analysis is presented. Selected experimental results show that the proposed control operates satisfactorily in case of a load step change, a load imbalance, and nonlinear loads.

Design of an Efficient 24–30 GHz GaN MMIC Power Amplifier Using Filter-Based Matching Networks

A broadband GaN MMIC power amplifier (PA) with compact dimensions of 1.94 × 0.83 mm2 is presented for 5G millimeter-wave communication. To guarantee output capability at the operating band edges where serious performance degradation is likely to occur, the appropriate large-signal matching model and optimal impedance domain need to be carefully determined through load-pull analysis. Broadband matching networks (MNs) in the lowpass form are thereafter developed based on the Chebyshev filter synthesis theory. Using high-pass interstage MN in conjunction with parallel RC lossy circuits to compensate for the transistor’s negative gain roll-off slope ensures a flat frequency response. The input MN is designed as a band-pass filter due to the reactance extracted from the input side of the stabilized device exhibiting series LC resonance characteristics. Measured on-wafer pulsed results for the proposed three-stage PA demonstrate up to 30.9 dBm of output power, more than 28.6 dB of small-signal gain, and a peak power-added efficiency (PAE) of 35.6% at 27 GHz. Both uniform gain and saturated output power (Psat) are achieved across 24–30 GHz with fluctuations of less than 0.8 dB.

Design and Applications of Integrated Transducers in Commercial CMOS Technology

Monolithic integration of Microelectromechanical Systems (MEMS) directly within CMOS technology offers enhanced functionality for integrated circuits (IC) and the potential improvement of system-level performance for MEMS devices in close proximity to biasing and sense circuits. While the bulk of CMOS-MEMS solutions involve post-processing of CMOS chips to define freely-suspended MEMS structures, there are key applications and conditions under which a solid, unreleased acoustic structure composed of the CMOS stack is preferred. Unreleased CMOS-MEMS devices benefit from lower barrier-to-entry with no post-processing of the CMOS chip, simplified packaging, robustness under acceleration and shock, stress gradient insensitivity, and opportunities for frequency scaling. This paper provides a review of advances in unreleased CMOS-MEMS devices over the past decade, with focus on dispersion engineering of guided waves in CMOS, acoustic confinement, CMOS-MEMS transducers, and large signal modeling. We discuss performance limits with standard capacitive transduction, with emphasis on performance boost with emerging CMOS materials including ferroelectrics under development for memory.

An Improved Compact Large-Signal GaN HEMT Model for Switch Application

The accurate current model near knee voltage is critical to precisely simulate the power compression characteristics for power high-electron-mobility transistor (HEMT), especially for high-power-switch applications. An improved compact large-signal gallium nitride (GaN) HEMT model for high-power-switch applications is proposed in this article. The proposed model employs an additional slope factor in terms of hyperbolic tangent function to improve the model accuracy and flexibility of the knee current in both positive and negative regions. Besides, the improved GaN HEMT model counting in intrinsic capacitance variation of drain–source capacitance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{\text{ds}}$ </tex-math></inline-formula> and gate–source capacitance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{\text{gs}}$ </tex-math></inline-formula> can characterize the nonlinear voltage-dependent performance of HEMT even when the HEMT is biased below pinchoff voltage. The modeling of intrinsic nonlinear capacitance below the pinchoff voltage achieves improved accuracy of isolation simulation for GaN HEMT switches under large-signal excitation. The proposed model is verified by measurements, including dc <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}{-}{V}$ </tex-math></inline-formula> characteristics, small-signal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -parameters, as well as large-signal power compression and harmonic characteristics. The proposed model will be useful for the design of RF switches.

Transient Stability Analysis and Improved Control Strategy for DC-Link Voltage of DFIG-Based WT During LVRT

In this paper, the transient stability for dc-link voltage of doubly-fed induction generator (DFIG)-based wind turbine (WT) is studied in detail during low voltage ride-through (LVRT). Firstly, referring to the rotor swing equation of synchronous generator (SG), the nonlinear large-signal model of dc-link voltage is established. In addition, the damping power, static slip power, and dynamic slip power are derived. Consequently, the transient performance of dc-link voltage under the different operation conditions of DFIG is revealed during LVRT. Furthermore, the instability form of dc-link voltage with the moving process of equivalent power angle is analyzed by the energy function of dc-link voltage. In addition, the impacts of dc voltage control loop's parameter, the active current of the stator, and the slip on the stabilization process of dc-link voltage are studied. Analysis result indicates that the insufficient damping and large unbalanced power would deteriorate the transient behavior and steady-state level of dc-link voltage. Therefore, an additional damping and slip power feedforward control strategy is proposed, which can make the transition process of dc-link voltage smoother and significantly improve the voltage steady-state level. Finally, simulation and experimental results validate the effectiveness of theoretical analysis.

A strategy dedicated to the concise and efficient development of the customized large-signal model for GaAs HEMTs

In this letter, a strategy dedicated to the concise and efficient development of the customized large-signal models for GaAs HEMTs is proposed, which is specialized for MMIC designers. The core concepts of the strategy are a deconstruction of the original thought of model construction and dimension reduction of the objective functions of optimization algorithms. The development of an Angelov-based customized large-signal model following this strategy has been successfully applied to GaAs HEMTs in 70nm process. The results show that it takes less than five minutes to execute such a parameter extraction algorithm with a one-button extraction function and good agreement is achieved between the model simulation and device measurement up to 65GHz.

Double-balanced mixer based on monolayer graphene field-effect transistors

Graphene field-effect transistors (GFET) have attracted much attention in the radio frequency (RF) and microwave fields because of its extremely high carrier mobility. In this paper, a GFET with a gate length of 5 μm is fabricated through the van der Walls (vdW) transfer process, and then the existing large-signal GFET model is described, and the model is implemented in Verilog-A for analysis in RF and microwave circuits. Next a double-balanced mixer based on four GFETs is designed and analyzed in advanced design system (ADS) tools. Finally, the simulation results show that with the input of 300 and 280 MHz, the IIP3 of the mixed signal is 24.5 dBm.

A Two-Stage Simultaneous Control Scheme for the Transient Angle Stability of VSG Considering Current Limitation and Voltage Support

Since the wide application of virtual synchronous generators (VSGs), the power grid faces great challenges in the safe and stable operation due to their limited thermal capacity and weak anti-disturbance ability. During transient period, for example, a fault occurs in the transmission line, the VSG may lose the transient angle stability and provoke the current hard limit. Even if the fault is cleared by tripping of line, it still faces the problem of instability and voltage dips. To address this problem, in this paper, the post-fault large-signal model of VSG is derived first via the travelling waves based fault information acquisition. Subsequently, with the effect of both active and reactive power loops taken into account, a two-stage simultaneous control scheme is proposed for improving the transient stability of VSG, while considering the current limitation during fault state and voltage support after fault clearance. This method is fulfilled by mode switching and an additional feedback control based on the fault signal. Finally, the effectiveness of the proposed method under both symmetrical and asymmetrical faults is verified. Moreover, the application of the proposed method in a multiple VSGs system is also verified. Besides, the robustness to parameter mismatch and the feasible operating region for the method are discussed.

A Compact Macromodeling Method for Characterizing Large-signal DC and AC Performance of InP and GaAs HBTs

In this paper, a compact macromodeling method for characterizing the large-signal characteristics of heterojunction bipolar transistors (HBTs) is proposed and successfully applied to describe the DC and AC performance of InP and GaAs HBT devices. Using the Symbolically-defined Device (SDD) technology, an empirical macro circuit preserving the Spice Gummel-Poon (SGP) intrinsic network and a simplified thermal network is established. The empirical current and charge functions are embedded in the SDD macro circuit network module. Compared with other large-signal models, the proposed model description and the relevant parameter extraction are relatively simpler, and at the same time, this method can maintain high fitting accuracy. To assess the validity and the accuracy of the proposed model, the compact large-signal model is constructed for 1 ㎛ InP HBT and 1 ㎛ GaAs HBT. Based on the complete extraction of the model parameters, excellent consistency is obtained between the measured and modeled results.

Scheduled Power Control and Autonomous Energy Control of Grid-Connected Energy Storage System (ESS) With Virtual Synchronous Generator and Primary Frequency Regulation Capabilities

This paper presents a combined control scheme for the grid-connected energy storage system (ESS). There are two control modes: the power control mode for the charging or discharging condition and the energy control mode for the stand-by condition. In the power control, a derivative element is added in the inertial power-frequency droop as a simple power system stabilizer to enhance the system damping. The energy control is developed from the power control by considering the energy storage dynamics. During system disturbances, both control modes are able to provide autonomous grid support. The small-signal model and the large-signal transient model of the ESS with the proposed control scheme are derived. As a result, the output power and&#x002F;or the stored energy of ESS is in proportional to the frequency deviation and will be restored to the pre-disturbance condition. By selecting appropriate control parameters, the stored energy is controlled within a safe range constrained by the frequency limits without manual interventions. The primary frequency regulation with both power-frequency and energy-frequency proportional relationships is realized by the energy control, which coordinates with the grid secondary frequency regulation. The control performance and the derived energy model are validated by detailed time-domain simulation studies.

An Evolutionary Multilayer Perceptron-Based Large-Signal Model of GaN HEMTs Including Self-Heating and Trapping Effects

Neural networks are widely used to build large-signal models; an appropriate network architecture is important for high model accuracy and good generalization ability. In this article, an evolutionary multilayer perceptron (EMLP)-based modeling approach is proposed to construct an accurate model with a proper architecture for GaN high electron mobility transistors (HEMTs). The multiobjective gray wolf optimizer (MOGWO) is used to optimize architectures, including the number of hidden layers and neurons. The two objective functions consist of the training error, generalization error, number of test cases, and number of parameters. An accurate EMLP-based model with a proper architecture is selected from the Pareto optimal solutions. The proposed method can be directly used to develop a large-signal model considering self-heating and trapping effects. Alternatively, to improve model accuracy and generalization ability, this approach is used to accurately model the effective trap potential and the bias- and temperature-dependent factor. The capacitance models are built with the EMLP and approximation. The large-signal model is implemented in Keysight Advanced Design System (ADS), and a good agreement is achieved between the measured and simulated results.

A Class-F Based Power Amplifier with Optimized Efficiency in Triple-Band

A Class-F mode-based power amplifier (PA) with optimized efficiency in triple-band was designed using a simple and systematic approach. By considering the second and third harmonic terminations of the PA, the relationship between the output impedance design space and the drain efficiency (DE) is extracted by large-signal model simulation. Then, a low-pass matching topology is utilized for the triple-band efficiency optimization. The method is justified by both simulation and measurement of a triple-band PA to integrate three functions into one hardware, i.e., 1518–1525 MHz for mobile communication, 2.1 GHz for telemetry and control, and 2.492 GHz for navigation signal transport. The proposed PA achieves a measured result of high DE (63% at 1.52 GHz, 71% at 2.1 GHz, 59% at 2.492 GHz) in the three bands with an output power of at least 40 dBm.

Hybrid particle swarm optimization‐grey wolf optimization basedsmall‐signalmodeling applied toGaNdevices

In this research, four different equivalent circuit models that characterize the substrate/buffer loading effect for GaN high electron mobility transistor (HEMT) on Si substrate have been investigated. Y-parameter measurements of an open de-embedded structure have been used to characterize this effect in GaN HEMT on Si. An optimization technique based on hybridization between two meta-heuristic techniques, which are particle swarm optimization (PSO) and grey wolf optimization (GWO) has been developed to extract physical relevant model elements. The proposed optimization technique is applied on GaN HEMTs of different sizes and validated by means of S-parameters fitting. In addition, the extracted elements are evaluated in terms of their reliability and scalability. The proposed PSO-GWO technique shows a very good agreement with previous research results. It has been found that the circuit topology of both resistive and capacitive shunt branches is more accurate in characterizing conductive and displacement substrate/buffer leakage current, respectively. The results of this research validate the applicability of the proposed technique and the model topology for small and large-signal modeling of GaN transistors on Silicon substrate.

(La,Ba)SnO3 -based Thin-Film Transistors: Large-Signal Model and Scaling Projections

Perovskite oxides are extremely interesting for their possible use in high-mobility thin-film transistors (TFTs) suitable for high-performance large-area circuits. Here we present a semianalytical model of a recently fabricated TFT based on ${\mathrm{La}\text{\ensuremath{-}}\mathrm{Ba}\mathrm{Sn}\mathrm{O}}_{3}$, and explore the possibilities for technology optimization and the intrinsic potential of the device concept for applications in transparent and flexible electronics. We show that ${\mathrm{La}\text{\ensuremath{-}}\mathrm{Ba}\mathrm{Sn}\mathrm{O}}_{3}$ TFTs can outperform existing TFT device technologies through a detailed benchmarking exercise, and that these devices can be promising for display electronics and for a broader range of applications.

Analysis and Suppression of the Frequency-Aliasing Phenomenon Related to the Sorting-Algorithm-Based Voltage-Balance Strategy in an MMC System

The frequency-aliasing phenomenon, which can distort high-frequency harmonics in the analog input signal into low-frequency harmonics in the output digital signal, is widespread in the process of analog to digital conversions. The sorting-algorithm-based voltage-balance strategy is also such a conversion process. This strategy converts the analog-continuous-sinusoidal fundamental wave into the digital-discrete inserted-submodule number, deciding how many submodules are required to operate in modular multilevel converters (MMC). Thus, the frequency-aliasing phenomenon can occur in this strategy and deteriorate the performance of MMC as well. This article first proposes the mechanism of the frequency-aliasing phenomenon in the sorting-algorithm-based voltage-balance strategy. A quantitative analysis is then presented to indicate the root cause of the frequency-aliasing phenomenon in the voltage-balance strategy. This analysis also intuitively describes the frequency-aliasing phenomenon's effect, such as harmonic redistributions in the large-signal model, the phase delay in the small-signal model, and the associated deteriorations including the system stability's decrease and the power quality's reduction. Based on the above analysis, an optimal value design method is proposed to suppress the frequency-aliasing phenomenon by determining an appropriate voltage-balance frequency. A code restructuration method is further implemented to adapt the voltage-balance strategy to the optimal frequency and to avoid extra switching actions at the same time. The deteriorations caused by the frequency-aliasing phenomenon and the effectiveness of proposed methods are finally demonstrated via simulations experiments.

Approach for Extreme Learning Machine-Based Microwave Power Device Modeling

The nonlinear representation of active devices plays an important role in microwave circuit design. Whereas, it takes a long time to extract a large amount of large signal data, and the problem of memory resource and CPU occupancy becomes significant. In order to address the problems in traditional large-signal modeling methods, in this paper an X-parameter modeling method for microwave power devices based on extreme learning machine (ELM) is proposed. To demonstrate the effectiveness of this method, a double layer back propagation (BP) neural network model is established. Then, harmonic balance simulations are used to verify the accuracy of these two models. After comparisons, it is proved that the three harmonic errors of double layer BP neural network model are 9.525dBm, 1.309dBm and 14.593dBm, respectively, and the three harmonic errors of ELM model are 0.673 dBm, 0.314 dBm, 3.09 dBm, respectively. Furthermore, the three harmonic modulus errors of double layer BP neural network model are 0.031, 0.002, 7.665e-4, respectively, and the errors of ELM model are 0.005, 0.001, 8.38e-5, respectively. Finally, in order to verify the accuracy of the predicted model in circuit design, the predicted X-parameter is used in the design of power amplifier. Moreover, the errors of the double layer BP neural network prediction model at 2.5 GHz, 5 GHz and 7.5 GHz are 1.142 dBm, 1.436 dBm and 2.294 dBm, respectively. The output power error of the ELM model at 2.5 GHz, 5 GHz and 7.5 GHz are 0.089 dBm, 0.311 dBm and 0.309 dBm, respectively. These experimental results demonstrate that the established ELM model is an efficient and valid approach for modeling GaN high electron mobility transistor types of nonlinear microwave devices.

Multi-segment fuzzy control for start-up optimizing of LCC-based high-voltage power supply

Widely applied in medical, industrial, and military fields, the high-voltage power supply based on LCC resonant converter (LCC) is ought to establish tens kilovolts of output voltage within milliseconds according to many standards. And any overshoot during this start-up process is not allowed because of the issue or even deadly consequence it may lead. Traditional linear control schemes are powerless to fulfill these two conflicting requirements, especially for the LCC with nonlinear gain characteristics. In this paper, a multi-segment fuzzy control is proposed to tackle this problem. Firstly, the nonlinear gain curve of LCC is piecewise linearized based on its large-signal model, and the control requirements for different segments are determined. Then the control parameters for each part are selected by an off-line fuzzy algorithm. The allowed minimum frequency during the start-up is also piecewise linearized so that the gain ability of LCC is utilized. Finally, the proposed control scheme is verified with an 80kW/150kV X-ray power supply. A low-cost controller is used to implement the start-up control scheme since the control parameters can be pre-calculated and stored in the controller. Compared with the commonly used linear PI control, the non-overshoot start-up time with the proposed control scheme is reduced by more than 60%.