Showing papers on "Small-signal model published in 2013"

Development of an 85-kW Bidirectional Quasi-Z-Source Inverter With DC-Link Feed-Forward Compensation for Electric Vehicle Applications

Abstract: This paper presents a detailed operation analysis, controller design, and realization of a high-power, bidirectional quasi-Z-source inverter (BQ-ZSI) for electric vehicle applications. The circuit analysis shows that with a bidirectional switch in the quasi-Z-source network, the performance of the inverter under small inductance and low power factor can be improved. Based on the circuit analysis, a small signal model of the BQ-ZSI is derived, which indicates that the circuit is prone to oscillate when there is disturbance on the dc input voltage. Therefore, a dedicated voltage controller with feed-forward compensation is designed to reject the disturbance and stabilize the dc-link voltage during a non-shoot-through state. An 85-kW prototype has been built. Both simulation and experimental results are presented to prove the functionality of the circuit and the effectiveness of the proposed control strategy.

Small-Signal Modeling of Open-Loop PWM Z-Source Converter by Circuit-Averaging Technique

Abstract: This paper presents the ac small-signal modeling of the power stage of pulsewidth-modulated Z-source converter in continuous conduction mode by the circuit-averaging technique. The small-signal models used to derive the open-loop power-stage input voltage-to-capacitor voltage, input voltage-to-inductor current, control-to-capacitor voltage, and control-to-inductor current transfer functions are derived. Open-loop power-stage transfer functions corresponding to the capacitor voltage loop and inductor current loop are derived. The transfer functions derived take into account the equivalent series resistances of the inductors and capacitors. Experimental validation of the derived small-signal models is presented for a laboratory prototype. The theoretical predictions are in good agreement with the experimental results.

I 2 average current mode control for switching converters

Abstract: The constant frequency average current mode control is a widely used control scheme for the converters requiring precise current control, but its transient response is relatively slow, while the switching loss and driving loss significantly diminish the light load efficiency. To solve these issues, the I2 control average current mode is proposed. By combining the fast direct current feedback and integral feedback, the I2 control achieves both wide bandwidth and accurate current control. As a particular embodiment of this concept, by adopting constant on-time modulation, constant on-time I2 control needs no artificial ramp, and has fast dynamic response. Moreover, due to the decrease of switching frequency, constant on-time I2 control improves the efficiency in discontinuous-conduction-mode. The concept of I2 control can be extended to other modulations. Small signal model using describing function based equivalent circuit model is proposed. The model is accurate up to 1/2 switching frequency. Based on model, the design guidelines are discussed. The proposed control is verified with simulation and hardware measurement results.

Small signal modeling of the Quasi-Z-Source-Inverter and a novel control strategy to minimize the influence of input voltage disturbances

Abstract: The Quasi-Z-Source-Inverter (QZSI) reveals an asymmetrical L-C-network structure in which unwanted oscillations can be triggered by input voltage disturbances (IVD). This paper presents an AC small signal model of the QZSI, derived from State Space Averaging, with emphasis on the influence of IVD. After the discussion of the small signal model, a novel cascade control strategy is developed to adequately compensate the influence of IVD on the DC-link voltage. The effectiveness of the proposed control strategy is verified by simulation and experimental results on a laboratory test bench with an induction machine as load.

Modeling and control of bidirectional DC-DC converter fed PMDC motor for electric vehicles

Abstract: This paper presents modelling and control design for a bidirectional dc-dc converter fed permanent magnet dc (PMDC) motor traction drive system for EV applications. The incorporation of the half bridge non-isolated bidirectional dc-dc converter improves the efficiency by allowing the provision for energy regeneration during braking (in the case of an EV or an HEV) and during down slope motion (in case of a pedalled electric bicycle). The state space averaging technique has been used to obtain the small signal model of the system. A unified PID controller working in both the modes i.e motoring and regeneration has been implemented for the speed control. The soft switching technique has also been incorporated to minimize the switching losses as well as to address the issue of parasitic ringing. The system model has been simulated in the MATLAB/SIMULINK and the results have been verified with the theoretical calculations.

Modeling and Simulation of Full-bridge Series Resonant Converter Based on Generalized State Space Averaging

Abstract: The small signal modeling technique based on the generalized state space averaging method is applied to single phase full-bridge resonant DC/DC converter .According to the simulation, the frequency characteristic curve is obtained from MATLAB, this paper analyzes the influence of the duty ratio, input voltage to frequency characteristics, then builds a closed loop simulation circuit with PSIM software, the simulation results show that, the small signal model has good controllability and anti disturbance resistance, generalized state space averaging method is more accurate to series resonant converter modeling.

Averaged modeling and control of a single-phase grid-connected two-stage inverter for battery application

Abstract: This paper proposes a small-signal averaged model and control design of a single-phase grid-connected two-stage inverter to comprehend its dynamic characteristics for battery application. However, when the circuit analysis of two-stage inverter is attempted at the same time, mathematical procedure for deriving its dynamic equation is very complex and difficult. The main idea of modeling for two-stage inverter is that bi-directional DC-DC converter or single-phase full-bridge DC-AC inverter is replaced with an equivalent current source, and then the dynamic equations for the separated converter and inverter are derived by using state-space averaging technique. The procedures for building the small-signal model of two-stage inverter is described in detail. Based on the derived small-signal model, the individual controllers are designed in a frequency-domain analysis. The input current and DC-link voltage controllers are used for converter, while the grid current controller is used for inverter. The simulation results illustrate that the validity of the proposed modeling approach and the controller design is well verified.

Single-Inductor Bipolar-Outputs Converter for the Supply of Audio Amplifiers in Mobile Platforms

Abstract: Listening music with a headset is now a classical feature of mobile phones A linear amplifier is still employed to drive the headset as the audio quality must challenge dedicated audio players with somewhat 100 dB of signal-to-noise ratio This feature must also have the lowest impact on the platform autonomy, size, and cost A symmetrical power supply is required by such audio amplifiers due to the standard jack connector of headsets Using an inductive switch mode power supply (SMPS) is the most energy efficient solution to supply audio amplifiers from a battery Classically, two dc/dc converters are employed to generate the required two symmetrical supply rails from a standard Lithium-Ion battery It is at the cost of numerous bulky and expensive external components A solution to reduce the number of external passive components is to consider a single-inductor, bipolar-outputs, (SIBO) dc/dc converter An early prototype of such a converter has been realized on a 130-nm silicon process and offers primary results, nonoptimal but promising The feedback control structure is studied based on a small signal model that serves to define the pairing of the loops for designing a decentralized controller A set of controllers is designed by a pole placement technique and transient performances are demonstrated on audio patterns thanks to a piecewise linear model of the converter Eighty percent peak efficiency is measured with the primary demonstrator but latter simulation results yield an expected improvement to 90% The audio specifications appear very constraintful and the proposed SMPS does not meet entirely the latter figures Limitations are detailed However, many other applications can benefit from the proposed SIBO dc/dc converter

Seamless dynamic model for bi-directional DC-DC converter

Abstract: In this paper, bi-directional DC-DC converter is analyzed using a seamless dynamic model with an independent voltage source and an independent current source, which polarity depends on the direction of the power flow. In the seamless dynamic model, the independent voltage source represents a battery and an independent current source represents the load or energy source. A small signal model is derived using a state space averaging method, and simulated results about the transient response characteristics are presented.

A new SEPIC inverter: Small signal modeling

Abstract: This paper presents a new inverter technology that is designed based on SEPIC converter. Small signal model and transfer functions of the inverter are obtained. The system demonstrates the existence of a non-minimum phase zero in positive peak and shift of that zero to left half plane to make the negative peak transfer function a minimum phase behavior. Simulations demonstrate that at various circuit parameter values, as the duty cycle increased in boost mode of operation, the transfer function zeros migrated towards the origin. Increasing the inductance values resulted in similar behavior. However, increasing the capacitance values resulted in a reduction in real part of the complex poles and zeros.

Small signal modeling of diode in a parallel module subjected to partial shading

Abstract: Parallel connection of solar cells results in a very small difference in the internal p-n junction voltages when operated under partial shaded conditions. A small signal model is proposed in this paper to analyze the changes in the module parameters of parallel cells operating under this conditions. From the analysis it is observed that the maximum power for a parallel configured solar module is obtained at a fixed output resistance under varied shaded conditions. Circuit simulations validated the model implemented in Matlab.

Modeling and Novel Modulation of Enhanced Z-source Inverter

Abstract: In this paper, an Enhanced Z-source inverter is proposed. Compared to the traditional Z-source inverter, it can obtain high voltage conversion factor with a short shoot-through duration, and can decrease Z-source capacitor voltage stress significantly. In order to identify its inherent character, the transient modeling of continuous conduction mode (CCM) in dc side is presented. Through the detailed analysis, a right-half-plane zero is found in its control-to–output function. Moreover, an improved control method for the Z-source inverter is proposed in this paper. In comparison with traditional maximum constant boost control method, this improved control method has noticeable advantages. Not only switching frequency can be reduced significantly but also the volume of the Z source can be lessened as a result of six shoot through states per carrier period while obtaining the same voltage boost gain. Simulation and experimental results have demonstrated the validity of small-signal models and the merits of the proposed control method.

Dead-beat controller with inductor current prediction for boost converter

Abstract: In order to improve the dynamic response of boost type DC/DC converter, a dead-beat controller with inductor current prediction is proposed. Firstly, the inductor current of the next two switching cycles is predicted based on the linear extrapolation method and the pulse-with modulation (PMW) duty ratios of them are adjusted to eliminate the difference between the predicted current and reference current. Then the small signal model of the voltage loop is analyzed for designing the PI controller. Compared with the conventional current controllers such as proportional-integral (PI) controller, the proposed dead-beat controller can not only avoid the oscillation problem when the PWM duty ratio exceeds 50%, but also improve the dynamic response greatly. Finally, the performance of the proposed controller is verified by experimental results.

Effect of Device Layout on the Stability of RF MOSFETs

Abstract: In this paper, the stability of RF MOSFETs is investigated in terms of the stability-factor ( $k$ -factor) for various layout schemes and device dimensions based on two different RFCMOS technologies. To systematically analyze the effect of small-signal device model parameters on RF MOSFET stability, the expression for $k$ -factor is derived as a function of the small-signal model parameters of RF MOSFETs. Based on the expression, the effect of small-signal model parameters on the stability of RF MOSFETs is explored along with its bias dependence. In addition, the effect of wiring schemes, number of gate fingers, gate finger pitch, and gate length is examined based on various device structures. It is shown that the transconductance and capacitances are the dominant device parameters to determine the stability of RF MOSFETs. The result also indicates that the stability of RF MOSFETs is strongly affected by the details of layout scheme and lateral dimension. Additionally, it was found that there is a tradeoff between device stability and speed. This study is expected to serve a guideline for the device design and optimization for stable operation of RF MOSFETs and circuits based on them.

Small signal transfer functions modeling and analysis for open loop KY converter

Abstract: The KY converter, which possesses fast load transient response and nonpulsating output current, is a good topology to overcome the drawback of the traditional nonisolated Boost converter and it will be gaining popularity in engineering applications in the future. In this paper, based on the averaging method, the small signal model of the open loop KY converter, which especially covers the energy-transferring capacitor and the switching frequency, is established and analyzed. The bode diagram of the corresponding derived transfer functions show that the energy-transferring capacitor and the switching frequency have an important influence on its dynamical behaviors. Finally, the effectiveness of the established small signal model and the correctness of the theoretical analysis are confirmed by the circuit simulation results from the PSIM.

Modeling, control and voltage unbalance compensation in a four-switch rectifier with input power factor correction

Abstract: In this paper, a small signal model is proposed for four-switch rectifier with input power factor correction. The required transfer functions are determined and calculated for a typical rectifier. This model is used to design an appropriate controller with defined characteristic to improve the rectifier performance. Another controller is used to compensate capacitors dc voltage difference. The system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the effectiveness of the proposed controllers.

Modeling and control of isolated full bridge boost DC-DC converter implemented in FPGA

Abstract: In this paper an isolated full bridge boost converter (IFBC) firstly is modeled. In the modeling part, a small signal equivalent of the converter is developed. From the small signal model, the converter transfer function is derived. Based on the obtained transfer function, challenges of controller design are discussed. In the next step a digital PI controller is designed and implemented in a FPGA to control the output voltage. Using the injection transformer method the open loop transfer function in closed loop is measured and modeling results are verified by experimental results.

Thermoelectric cooling for power electronics circuits: Small signal modeling and controller design

Abstract: This paper discusses the modeling and application of Thermoelectric Cooling (TEC) in power electronics circuits, with the focus on the small signal modeling and controller design. In this paper, the small signal analysis based on a comprehensive thermoelectric model is carried out and the results show that, the whole system is a non-minimum-phase system and lack of damping to the disturbance in the control variable. A closed loop controller is designed to solve the stability issues and realize dynamic temperature control. To verify the effectiveness of derived small signal model and designed controller, an 8 kW prototype has been built and experimental results are presented in this paper.

Modeling, control and stability analysis of VSC-HVDC links embedded in a weak multi-machine AC system.

Abstract: Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2013

Design of a digital control system for DC-DC converters to power electromagnets

Abstract: DC-DC converters are used at the Advanced Photon Source (APS) at Argonne National Laboratory to power electromagnets. A highly accurate control system is required for the DC-DC converters. This paper describes the design and evaluation of a digital control system to regulate the output current and reduce noise coupled in the system. A digital controller is first designed based on the small signal model of the converter. Experimental data of the output current is analyzed. Several types of digital filters are then designed to reduce the noise in the output current. The complete control system is then simulated and results are evaluated.

Performance prediction of switched reluctance generator with time average and small signal models

Abstract: This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages. First, a switching model is developed based on quasi-linear inductance profile. Next, based on the switching behaviour, a time average model is obtained to measure the difference between the excitation and generation time in each switching cycle. Finally, to track control voltage and current wave shapes, a small signal model is designed. The effectiveness of the complete multilevel model combining electrical machine, power converter, load and control with programming language is demonstrated through simulations. A PI controller is used for controlling the voltage of the generator. The results presented show that the controller exhibits accurate tracking control of load voltage under different operating conditions. This demonstrates that the proposed model is able to perform an accurate control of the generated output voltage even in transient situations. The simulation is performed to choose the control parameters and study the performance of switched reluctance generator prior to its actual implementation. Initial experimental results are presented using NI-Data acquisition card to control the output power according to load requirements.

Improving performance of a DC-DC cascaded converter system using an extra feedback loop

Abstract: This paper introduces the extra feedback method as a technique to improve the performance of a cascaded converter system and stabilize its operation. In this paper, first, the block diagram representation of the small-signal model of a single converter is presented. The open-loop and closed-loop transfer functions of this converter are provided in this stage as well. Next, the presented model is expanded to the block diagram model of a cascaded converter system comprised of two dc-dc converters. Then, the extra feedback method which is the main contribution of the paper is introduced. Some design guidelines for applying this method to an experimental cascaded converter system are provided in this part as well. Finally, some experimental results are provided to verify the theoretical outcomes.

Analysis and study of high DC/DC boost converters

Abstract: This paper presents the analysis and study of high dc/dc boost converters; boost converters have become important in applications for energy generation and even more if they have high gain. High efficiency, few components, low voltage and current stress on switches are features desired in these kinds of converters, but also its complexity to be controlled. In this paper three boost converters are analyzed: the traditional one, the tapped boost converter and specially a hybrid one: the analysis is made from the control point of view. The steady-state analysis and the small signal model of the topologies are shown. But also experimental results of one converter are presented to illustrate the behavior of the system for an output power of 50W.

Design of Gate-All-Around Tunnel FET for RF Performance

Abstract: This paper presents the design, radio frequency (RF) performance and high frequency stability of Gate-All-Around Tunnel Field Effect Transistor (GAA TFET). The small signal parameters that can be extracted using a non-quasi static small signal model are calculated using extracted parameters from a technology computer-aided design (TCAD) simulation. RF parameters like cut-off frequency (ft), maximum oscillation frequency (fmax) and stability factor (K) are extracted to evaluate the high frequency performance of GAA TFET. The result shows that the GAA TFET has cut-off frequency of 22GHz and unconditionally stable from 1GHz onwards. General Terms VLSI, RF

A new approach to extracting the RF parameters of asymmetric DG MOSFETs with the NQS effect

Abstract: In analog circuit design an important parameter, from the perspective of superior device performance, is linearity. The DG MOSFET in asymmetric mode operation has been found to present a better linearity. In addition to that it provides, at the discretion of analog circuit designer, an additional degree of freedom, by providing independent bias control for the front and the back gates. Here a non-quasi-static (NQS) small signal model for DGMOSFET with asymmetric gate bias is proposed for extracting the parameters of the device using TCAD simulations. The parameters extracted here for analysis are the intrinsic front and back gate to drain capacitance, Cgd1 and Cgd2, the intrinsic front and back distributed channel resistance, Rgd1 and Rgd2 respectively, the transport delay, τm, and the inductance, Lsd. The parameter extraction model for an asymmetric DG MOSFET is validated with pre-established extracted parameter data, for symmetric DG MOSFET devices, from the available literature. The device simulation is performed with respect to frequency up to 100 GHz.

Research on TZSI Control Method

Abstract: In transformer-Z-source inverters (TZSI), the impedance networks consist of a transformer and one capacitor. While maintaining the main features of traditional Z-source network, the new networks exhibit some unique advantages, such as the increased voltage gain and reduced voltage stress in the voltage-fed TZSI, when the turns ratio of the transformer windings is over 1. This paper contributes to the ac small signal modeling and analysis of TZSI in continuous conduction mode. The ac small signal model considers the dynamics introduced by network uniquely contained in TZSI. And a double loop control method which is impedance source network output dc voltage and current loop has been proposed to realize the control of TZSI. Results of simulations and experiments are used to validate the control method and show that this method is correct and feasible.

Dynamics on a ZCZVT soft-switching DC/DC boost converter

Abstract: The non-floating switches, zero-current–zero-voltage-transition (ZCZVT) soft-switching DC/DC boost power converter is proposed in this article. The AC small-signal mathematical model for the ZCZVT boost converter is then derived. It shows that the ZCZVT boost converter exhibits better dynamical behavior than the conventional PWM boost converter. The accuracy of theoretical results is verified by experiments and simulations. In addition, a classical and a modified integral variable structure controllers are designed to achieve output voltage regulation. They are used to eliminate the effect of the variations of input voltage and load on the output voltage. The performances of the proposed converter with these controllers are also validated by experimental results.

Study of PI Adaptive Non-Linear Control Strategy Based on CCM/DCM Fast Identification for DC/DC Converter

Abstract: An isolated three-level H-bridge high-capacity DC/DC converter is a good solution for transferring energy from middle-voltage network to low-voltage network. The transformer can be smaller and lighter with high working frequency, so phase shift Pulse-Width Modulation (PWM) is used by converter. The small signal model has been built by theoretical derivation and verified by simulation when the converter working on Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). The analyze results indicated that the mathematic models and dynamic properties were different when converter working in disparate mode. Therefore, the PI parameters of the controller can be hardly chosen to reach the excellent dynamic performance when the converter meets the large disturbance of mode change. That is, you can hardly find a group of PI parameters for converter working well in all load range. Aiming at it, A PI adaptive non-linear control strategy based on CCM/DCM fast identification has been proposed. The fast mode identification was based on inductor voltage characters, and the mode information wound send out in less than a switching period. So, the PI parameters can be instantaneous changed by mode signal to achieve the best dynamic property. The operation principle and analyze result of the control strategy is verified by the prototype at last.

All Mode Small Signal Model and Controller of Three-Level DC DC Converter

Abstract: To design a preferable controller for the three-level H-bridge DC/DC converter,the topology of the circuit and principles of the converter with phase-shift PWM control are analyzed,so all the working modes both in CCM and DCM period get visible,the small signal models are thus established in CCM and DCM with average state space method and average switched network method,and their correctness is verified by the simulationsFollowing the small signal models,a double loop PI mode adaptive controller is designedThe comparative experiments for the new controller and the conventional PI one show that the changed mode results in a bad dynamic output,and the new controller adjusts the parameters instantaneously by mode examinationThe output voltage droop of the new controller reduces by 466% compared with the common PI controller case under sudden loading

A new approach to extracting the RF parameters of asymmetric DG MOSFETs with the NQS effect

Abstract: In analog circuit design an important parameter,from the perspective of superior device performance,is linearity.The DG MOSFET in asymmetric mode operation has been found to present a better linearity.In addition to that it provides,at the discretion of analog circuit designer,an additional degree of freedom,by providing independent bias control for the front and the back gates.Here a non-quasi-static(NQS)small signal model for DGMOSFET with asymmetric gate bias is proposed for extracting the parameters of the device using TCAD simulations.The parameters extracted here for analysis are the intrinsic front and back gate to drain capacitance,Cgd1and Cgd2,the intrinsic front and back distributed channel resistance,Rgd1and Rgd2respectively,the transport delay,m,and the inductance,Lsd.The parameter extraction model for an asymmetric DG MOSFET is validated with pre-established extracted parameter data,for symmetric DG MOSFET devices,from the available literature.The device simulation is performed with respect to frequency up to 100 GHz.