Showing papers on "Small-signal model published in 2009"

Accurate Small-Signal Model for the Digital Control of an Automotive Bidirectional Dual Active Bridge

Abstract: The derivation of an accurate small-signal model for a galvanically isolated, bidirectional dc-dc converter and the implementation of a corresponding controller on a DSP as well as key methods and functions required for the digital implementation are detailed in this paper. The investigated dc-dc converter, an automotive dual active bridge (DAB) system, enables power transfer between a low-voltage port (ranging from 11 to 16 V) and an HV port (240 to 450 V). The nominal power rating is 2 kW. The developed small-signal model yields highly accurate results for the DAB system, but the proposed modeling procedure could also be applied to arbitrary resonant power converters with unidirectional or bidirectional power transfer.

Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter

Abstract: An accurate small-signal model of three-phase photovoltaic (PV) inverters with a high-order grid filter is derived in this paper. The proposed model takes into account the influence of both the inverter operating point and the PV panel characteristics on the inverter dynamic response. A sensitivity study of the control loops to variations of the DC voltage, PV panel transconductance, supplied power, and grid inductance is performed using the proposed small-signal model. Analytical and experimental results carried out on a 100-kW PV inverter are presented.

Small-Signal Model-Based Control Strategy for Balancing Individual DC Capacitor Voltages in Cascade Multilevel Inverter-Based STATCOM

Abstract: This paper presents a new feedback control strategy for balancing individual DC capacitor voltages in a three-phase cascade multilevel inverter-based static synchronous compensator. The design of the control strategy is based on the detailed small-signal model. The key part of the proposed controller is a compensator to cancel the variation parts in the model. The controller can balance individual DC capacitor voltages when H-bridges run with different switching patterns and have parameter variations. It has two advantages: 1) the controller can work well in all operation modes (the capacitive mode, the inductive mode, and the standby mode) and 2) the impact of the individual DC voltage controller on the voltage quality is small. Simulation results and experimental results verify the performance of the controller.

Analysis and Design of Maximum Power Point Tracking Scheme for Thermoelectric Battery Energy Storage System

Abstract: The analysis and design of an adaptive maximum power point tracking (MPPT) scheme using incremental impedance are presented. A small-signal model is mathematically derived, and the impact of two major design parameters, which are scaling factor and sampling interval, is analyzed in the frequency domain. Four factors which specifically affect the MPPT response are also clearly addressed. Based on this analysis, a design methodology to achieve a desirable transient response, while retaining system stability, is developed. The design methodology is implemented and verified with hardware experiments on a thermoelectric generator battery energy storage system, which indicate agreement between dynamic response and target bandwidth.

Phasor-Domain Modeling of Resonant Inverters for High-Frequency AC Power Distribution Systems

Abstract: The circuit modeling and analysis of resonant inverters is complex because the state variables such as inductor currents and capacitor voltages are AC dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonic of interest. Correspondingly, the circuit is decomposed into two DC subcircuits, the state variables of which are the time-varying Fourier coefficients of the original AC variables. A small-signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A phasor-domain modeling method is used to investigate the resonant inverters in high-frequency AC power distribution systems. A resonant inverter system with five energy storage elements is modeled and simulated, and compared with switch simulation for both steady state and transients. The phasor model simulation matches the switch model simulation in both steady state and transients, but takes much less computing time. In addition, this model closely relates to the power converter topology in time domain, and therefore, keeps the physical meaning of the state variables. It can be used for high accuracy of modeling, simulation, and circuit analysis and control design. It can be extended to a higher order of resonant topologies including parasitic components. A high-frequency AC system with two pulse-phase-modulation-controlled resonant inverters is modeled and simulated, and the current distribution control is investigated with the phasor model. The model simulation is compared with switch-level simulation and experimental results.

Small-signal modeling and analysis of battery-supercapacitor hybrid energy storage systems

Abstract: The battery/supercapacitor hybrid energy storage system actively combines two energy storage devices to achieve better power and energy performances. This paper presents a detailed small-signal mathematical model that can represent the dynamics of the converter-interfaced energy storage system around the steady-state operating point. This model takes into account the effects on the currents of a variety of factors such as the voltage-current characteristics of individual energy storage devices, power converter and filter parameters, and controller parameters. The proposed model considers the variations in the battery current, supercapacitor current and DC bus voltage as state variables, the variations in the power converter duty cycles as the control input, and the variations in the battery voltage, supercapacitor voltage and load current as external disturbances. Frequency-domain model and control strategies for the power sharing between the battery and supercapacitor are developed based on the small-signal model of the hybrid energy system. Frequency-domain characteristics of the open-loop and closed-loop systems are analyzed. Time-domain simulation is used to verify the system operation. The effects of system and controller parameters on the system performance are also studied.

Modeling and Analysis of Hysteretic Current Mode Control Inverter

Abstract: In this paper, a small signal model of hysteretic current mode control with variable frequency and fixed hysteretic band is presented, based on three terminal averaged switch cell of buck converter in continuous current mode. This model reveals that the averaged current is the control target of hysteretic control. And phase lag of current loop with high switching frequency is quite small that makes current loop equivalent power stage be a proportional component. The conclusion is also valid in large signal analysis. Then an averaged linear model of single phase inverter is derived. The order of the system closed loop characteristic equation is reduced due to hysteretic current control introduced. And compensation principles of a single phase inverter are investigated with Routh criterion, which is easy to implement in practice and a good comprise between stability and stable/dynamic performance could be achieved.

Small signal characterization of fluorescent lamps in dimmed operation

Abstract: In recent bibliography, several small signal models for fluorescent lamps have been presented. These models are focused in the characterization of the lamp small signal dynamic impedance at nominal power level. This impedance can only be used to analyze the lampballast interaction at nominal power. However, in dimming ballasts, the interaction between lamp and ballast can lead to system instability at reduced power operation. In present paper, the small signal model of a compact fluorescent lamp is obtained at different power levels. At each power level, the parameters of the single-pole, single-zero model are obtained. The static gain, pole and zero frequencies of the model are calculated and fitted to a power dependent polynomial expression. Using the generalized multi-frequency averaging technique the stability of a voltage controlled resonant inverter is analyzed. The stability margin of the system is calculated using the proposed model and verified using an experimental prototype.

Small signal model for Boost Phase-shifted Full Bridge converter in high voltage application

Abstract: Boost Phase-shifted (PS) Full-Bridge (FB) converter is a typical converter in high voltage application. Due to the requirement of high voltage insulator, its transformer is often designed with more leakage inductor and inter-layer capacitor. Considering leakage inductor and inter-layer capacitor's effect, accurate model of Boost PS FB converter is established. The difference between this model and the conventional model is analyzed. Based on this model, the closed-loop small signal model with average current-mode control is also given. The experimental results on a 530V/15kV, 5kW prototype proved the theoretical analysis.

Analysis and Design of a Single-Phase PWM Rectifier Based on the Small Signal Model

Abstract: The single-phase voltage source PWM rectifier VSR is widely used in improving the quality of the power energy. Recently, lots of researches have been investigated for the Single-Phase PWM rectifier. The PWM rectifier based on the small signal model is proposed in this paper. The new single-phase PWM rectifier with compensate circuit improves the dynamic performance of the system . Also, the output voltage fluctuation is reduced obviously. Simulation results are presented to verify the feasibility and effectiveness of the proposed method. Keywordssingle-phase; PWM rectifier; small signal model

Design of Multiple-Input DC-DC Converter Control System for Fuel Cell Electrical Vehicle

Abstract: A multiple-input Triple-Half-Bridge (THB) bidirectional dc-dc converter is presented when this THB converter is applied to the fuel cell electrical vehicle drive system. A dual close-loop control system is designed through bode diagram. Decoupling network is designed to obtain better control performance. Finally, the analysis and design validation are verified through the experiment.

A Unified Compensator Design Based on Instantaneous Energy Equilibrium Model for the DC Link Voltage Control of UPQC

Abstract: Suitable model for the analysis and control of the Unified Power Quality Controller (UPQC) was quite difficult to obtain, which prohibited not only the analysis and comparison between existing control strategies, but also the industrial applications, as no generalized method to design the control loop for different disturbances. In this paper, a unified DC voltage compensator design is proposed for UPQC based on the system instantaneous energy equilibrium model. The main circuit model of UPQC is derived firstly, including both the steady state model and the small signal model. Subsequently, four existing control strategies for the shunt converter control are found and modeled in detail, which are combined with UPQC main circuit model, and the whole control system are obtained accordingly. The UPQC whole system model are compared and evaluated in different disturbances. And then the unified compensator design method for the DC link voltage control is proposed, the worst control strategy is then chosen as an example for the detailed compensator design, based on the newly proposed model. Finally, the computer simulation and prototype experiment are done to verify the validity all the analysis and control.

The Research of Modeling and Simulation for Phase-shifted Full-bridge ZVS DC / DC Converter

Abstract: On the basis of the analysis of phase-shifted full-bridge ZVS PWM converter, Corresponding small-signal model is build using of state-space averaging method and the traditional Buck circuit model, Thereof, control block diagram of the system and transfer function are derived, Voltage single-loop control system is designed on the basis of small-signal model of phase-shifted full-bridge ZVS converter, Thus, the system is analyzed and PI compensation network is correctly designed. Finally, it is simulated using of matlab and simulation map is given, The results shows that the mathematical model is rational and design scheme is feasible.

Small signal analysis and closed loop control design of L-L type active-clamped ZVS current-fed isolated DC-DC converter

Abstract: This paper presents the small signal model and closed loop control design using average current control for an L-L type active-clamped zero-voltage switching (ZVS) current-fed isolated DC-DC converter. State-space averaging technique is used to derive the small signal model. The controller is designed for fixed-frequency duty cycle modulation and works for wide input voltage and load variation. A complete design procedure is presented. Frequency response curves are obtained at different input voltage and load conditions to verify the stability and design, and to evaluate the performance of the controller. Simulation results for step changes in input voltage and load are given to check the transient response of the converter.

An Introduced Neural Network-Differential Evolution Model for Small Signal Modeling of PHEMTs

Abstract: Since neural network algorithms are able to model nonlinear relations between different data sets, an introduced neural network model (INN) based on a generalized differential evolution training algorithm (INN-DE) is presented for pseudomorphic high electron mobility transistor (PHEMT). This global optimization algorithm is applied to avoid the local minima problem in the gradient descent-training algorithm and to achieve acceptable solution. The main advantage of this technique is its validation in wide range of frequencies and high accuracy for the small signal characteristics. The proposed (INN-DE) model is used to predict the scattering parameter values for various bias values different from the ones in the data set used for training. This model has been verified by comparing predicted and measured values of a PHEMT for a certain data set of S-parameters at different frequencies and bias points

Averaged large signal model of boost power factor corrector in boundary conduction mode

Abstract: A modeling approach of a power factor correction circuit operating in boundary conduction mode is presented. The PFC is controlled by a constant on-time of the switch. The effect of valley switching is simplified and taken into account as dead-time to generate a large signal model. On the basis a small signal model for the constant on-time controlled PFC voltage loop is derived. The large and small signal models are compared to measurements of the transfer function. For performing this low frequency transfer functions measurement a set-up using an oscilloscope and functional generator is described.

Small-signal model parameter extraction for microwave SiGe HBTs based on Y- and Z-parameter characterization

Abstract: High frequency intrinsic small-signal model parameter extraction for microwave SiGe heterojunction bipolar transistors is studied, with a focus on the main feedback elements including the emitter series resistor, internal and external base-collector capacitors as well as the base series resistor, all of which are important in determining the behavior of the device equivalent circuit. In accordance with the respective features of definition of the Y- and Z-parameters, a novel combined use of them succeeds in reasonably simplifying the device equivalent circuit and thus decoupling the extraction of base-collector capacitances from other model parameters. As a result, a very simple direct extraction method is proposed. The proposed method is applied for determining the SiGe HBT small-signal model parameters by taking numerically simulated Y- and Z-parameters as nominal "measurement data" with the help of a Taurus-device simulator. The validity of the method is preliminarily confirmed by the observation of certain linear relations of device frequency behavior as predicted by the corresponding theoretical analysis. Furthermore, the extraction results can be used to reasonably account for the dependence of the extracted model parameters on device geometry and process parameters, reflecting the explicit physical meanings of parameters, and especially revealing the distributed nature of the base series resistor and its complex interactions with base-collector capacitors. Finally, the accuracy of our model parameter extraction method is further validated by comparing the modeled and simulated S-parameters as a function of frequency.

Small-signal model of bumbleBee output voltage controller for DC/DC converter

Abstract: During two previous MIXDES conferences author presented new method of controlling DC/DC converters, which uses law of conservation of energy. Developed theory was confirmed by both simulation results and measurements conducted on the constructed prototype. Now in the following paper, the small-signal model of the proposed controller is presented along with proof of stability for presented method of stabilization of converter's output voltage. In the paper the results of measurements that allow determination of the accuracy of the model are also presented.

Microwave noise modeling for PHEMT using artificial neural network technique

Abstract: An improved noise model for pseudomorphic high electron mobility transistors (PHEMT) based on the combination of the artificial neural network (ANN) and conventional equivalent circuit modeling technique is presented. The frequency dispersion of the gate noise model parameter P, drain noise model parameter R, and the correlation coefficient C have been taken into account by using an ANN model. The influence of the gate leakage current can be accommodated by using the proposed noise model. The noise model parameters are determined directly from on wafer noise parameters measurement based on the noise correlation matrix technique. Good prediction for noise parameters and significant improvements of the accuracy of noise parameters are obtained up to 26 GHz for 2 × 40 μm gate width (number of gate fingers × unit gate width) 0.25 μm Double Heterojunction δ-doped PHEMTs over a wide range of bias points. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.

Small signal modeling of a novel single-phase photovoltaic inverter

Abstract: The dual mode time-sharing photovoltaic (PV) inverter is generally of higher efficiency compared to other types because only one power stage operates in the high switching frequency state at any time. In this paper, small-signal-model comparison was made between the conventional dual mode time-sharing inverter and the proposed dual mode time-sharing cascaded inverter. It has been revealed with modeling that the control-to-output voltage transfer function of the conventional inverter has right half plane zero, and the system is difficult to be controlled well, additionally, a simple compensator could hardly meet the requirement on system's phase margin and amplitude margin when the input voltage is lower than a half peak value of the output voltage. However, it becomes much easier to design a desired compensator for the proposed buck-type inverter. The experiments in a 1kW prototype of proposed inverter verified the theoretical analysis.

Dead-band controller for balancing individual dc capacitor voltages in cascade multilevel inverter based STATCOM

Abstract: This paper presents a dead-band controller for balancing individual dc capacitor voltages in a three-phase cascade multilevel inverter based static synchronous compensator (STATCOM). The design of the feed-back control is based on the detailed small-signal model. The proposed dead-band controller can stabilizes the phase shift of H-bridge voltages, and then reduces the risk of unnecessary switching of power semiconductors. The controller can balance individual dc capacitor voltages when H-bridges run with different switching patterns and have parameter variations. Moreover, it is shown that the controller can work well in all operation regions. Experimental results verify the performance of the controller.

Research on design method of control system for three-phase voltage source PWM rectifier

Abstract: The mathematical model in dq axis of three-phase PWM rectifier’s main circuit is set up in this paper.Current control with feed-forward and decoupling strategy is selected.The double loop control system is designed and the stable DC voltage and the high power factor of the PWM rectifier are regulated by three PI controllers.By building the small signal model of transfer function from the voltage loop’s output to the DC bus voltage,the control block diagrams of the voltage loop and the current loops are set up,then their PI controllers are designed.At the end of the paper,simulation and experimental results are given to verify the proposed analysis and design.

Small-Signal Modeling of Power Electronic Converters with Resonant Controllers

Abstract: While time domain electromagnetic transient simulation is an incredibly powerful tool for the analysis of large signal events in power systems, many small-signal phenomena may alternatively be studied using eigenvalue analysis and/or transfer functions. Eigenvalue or transfer function based analysis requires system linearization to be carried out about a static operating point. In the case of power systems, where voltage and current signals are AC, linearization is made possible through use of the synchronous or dq reference frame transformation. Since machine models and models of most FACTS devices and their controllers are readily available in the dq-frame, the process of linearizing such equipment is relatively straight-forward. Recently, resonant controllers have emerged as an alternative to dq-frame controllers for regulation of grid connected converters, both in FACTS devices and in interface converters for distributed resources. Although these control systems behave somewhat similar to dq-frame controllers under balanced operating conditions, their behaviour under unbalanced operation is unique. This paper develops a small signal model of a VSC system, where resonant current controllers are used for regulation of the grid currents. Dynamics of a DC voltage control loop are included. Small signal dynamics are validated against time domain simulation.

The small signal model for wireless parallel operation of inverters

Abstract: In this paper, a modelling method for the parallel operation of inverters in a micro-grid system is proposed. Conventionally, the droop method has been applied to achieve a simple structure and no-interconnections among power sources. The small signal model of the wireless parallel inverter allows obtaining the behaviour of the system in function of frequency and voltage droop. The model is simple and eases to unstainable, and can give reference to the next step for the dynamic stability analysis and dynamic equivalency in power system. Simulation has been carried out on the system with two inverters in parallel. The results have validated the model developed.

Dynamic modeling and robust control of multi-module parallel soft-switching-mode rectifiers

Abstract: In this paper, small-signal modeling and robust controller design for multi-module parallel soft-switching mode rectifiers (SSMRs) are presented. First, a single-phase boost-type SSMR is formed from the traditional boost-type switching mode rectifier (SMR) with auxiliary resonant branch to achieve zero-voltage-transition (ZVT) soft switching for the main and auxiliary switches. Based on the proposed single-phase SSMR, parallel operation of multi-module single-phase SSMR is made for increasing the total power capacity and the reliability of the SSMRs. The state-space averaging method is employed to derive the small signal model of the SSMR in current control loop for performing its current controller design. As for the voltage control loop, the dynamic model of the multi-module SSMR is derived at nominal case by averaging method for two-time-scale (AM-TTS) and averaged power method. Then, the quantitative and robust voltage regulation controls are proposed for multi-module SSMR to improve the control performance when the parameter variations caused by system configuration change and operating point shift have occurred. The accuracy of the derived SSMR dynamic model and the effectiveness of the proposed controller are demonstrated by some simulation and experimental results.

Improvements to the extraction of an AlGaN/GaN HEMT small-signal model ∗

Abstract: The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in large-signal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract Rg. In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S 11 and S 22 is improved, and fT and fmax can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S -parameters in the range of 0.1 to 26.1 GHz.

Analysis of medium-frequency oscillation in the Boost power factor correction converter with average current mode control

Abstract: On the assumption that the input voltage can be replaced by its RMS value and the frequencies of the inductor current and the output voltage are much lower than the switching frequency of the converter, the small-signal model of Boost PFC converter is constructed and the medium-frequency oscillation in Boost PFC converter is studied. The underlying mechanism of this nonlinear phenomenon is analyzed and the stability conditions are also given. These obtained results indicate that this type of nonlinear phenomenon is different from the fast- and slow-scale instabilities, and the main characteristic of this type of nonlinear phenomena is that its oscillation frequency lies between the line frequency and the switching frequency. Finally, an experimental circuit is designed, and its experimental results agree very well with the simulation results.

Small-signal Model of BumbleBee Output Voltage Controller for DC/DC Converter Stability Analysis of BumbleBee Method

Abstract: During two previous MIXDES conferences author presented new method of controlling DC/DC converters, which uses law of conservation of energy. Developed theory was confirmed by both simulation results and measurements conducted on the constructed prototype. Now in the following paper, the small-signal model of the proposed controller is presented along with proof of stability for presented method of stabilization of converter's output voltage. In the paper the results of measurements that allow determination of the accuracy of the model are also presented.

A physical-model of small-signal InP-based double heterojunction bipolar transistors and its parameter extraction technique

Abstract: The influence on the base-collector junction capacitance Cbc of the energy band structure of the InP heterojunction bipolar transistors is researched. A physical model of small-signal InP double heterojunction bipolar transistor （DHBT） is developed, which takes into account the base-emitter and collector-emitter metalisations by using two additional capacitances Cmb and Cmc. The resistance of the model is divided into the intrinsic resistance, the extrinsic resistance and the parasitic resistance. Meanwhile, a physically meaningful small-signal parameter extraction procedure for the model is presented, in which all the equivalent circuit elements are extracted without reference to numerical optimization. An experimental validation is carried out, and excellent results are obtained over a wide range of bias points, which demonstrates good modeling accuracy.

Averaged small-signal modeling of a non-isolated single-stage single-switch AC/DC converter

Abstract: A transformerless single-stage single-switch AC/DC converter was reported and analyzed recently The converter features high power factor capability, high conversion efficiency, reduced voltage stress on bulk capacitor, low manufacturing cost and small in size In this paper, its averaged small signal model is analyzed and presented for the control purpose By applying small ac signal perturbations and statespace averaging technique, the crucial dynamic transfer functions are derived Bode plots of the transfer functions are also given for designing the controller The experimental results validate the model and show in good agreement