PWM Switch Model Research Articles

A PWM Switch Model of Isolated Battery Charger in Constant-Current Mode

In this paper, the pulsewidth modulation switch method was used to investigate the effect of the transformer leakage inductance on the small-signal model in isolated full-bridge converter. A galvanic isolated hard-switching full-bridge converter that operates in constant-current mode is analyzed, confirming that leakage inductance significantly affects the small-signal model, and the influence of leakage inductance can be equivalent to a resistance in series with the converter's output LC filter just as that in phase-shifted full-bridge converter. However, the same leakage inductance in these both converters will lead to different equivalent resistance due to different operating principles. Results of the modified model, simulations, and the experiments are compared to verify the correctness of the model. Moreover, this paper also shows that the Norton equivalent circuit of the charger operates in constant current mode, which can be used to estimate the dynamic behavior of the system.

DC transformer modeling and control of DC-DC buck converter

Switching Power Converters convert one form of power to another with high ef-ciency and accurate control.One of the most widely used DC-DC Converter is Buck Converter. Control is invariably required to maintain the output voltage/current in spite of variations in source/load. In order to design the controller and gain insight about the system a dynamic model needs to be developed. Modeling techniques widely used are state space averaging and PWM switch model. In this paper DC transformer modeling technique is used to develop the averaged model of the converter. One of the advantages of this model is that it can be implemented in Spice simulator using basic circuit elements. The same model can be used for time domain as well as frequency domain analysis. Analog type-II compensator is designed to compensate the system. Simulation and experimental results for start-up transient and load transient are shown to validate the model.

Analysis of the Response of L and LCL Filters in Controlled Rectifiers used in Wind Generator Systems with Permanent Magnet Synchronous Generators

This paper presents the comparative study of the response of a Controlled Rectifier in a wind power system with a synchronous permanent magnet generator when a L filter and a LCL filter are used between the generator and the rectifier. The Rectifier is modeled considering an L filter and an LCL filter. In addition, the PWM switch model is used to linearize the controlled rectifier and obtain the equivalent circuit at the operating point and the equivalent circuit at small signal. From the equivalent small signal circuit, the transfer functions of the rectifier are obtained. These transfer functions are used to implement rectifier control loops. One of the main advantages of using the switch model in the rectifier is that it allows the rectifier to be simulated without the control loops. This allows a comparison of the variables of the rectifier with different filter types, in this case, a L filter and a LCL filter. The Duty cycles are calculated from the operating point circuit. In addition, the rectifier is simulated in open loop with a sinusoidal modulation. This in order to analyze which filter is better in terms of Total Harmonic Distortion and efficiency. From the results obtained from the simulation, the rectifier with the L filter has a better performance in the total harmonic distortion in current and efficiency (THDi=4.85%, FP=99.8729% y E_ff=99.99%) compared to the rectifier with the LCL filter (THDi=7.91%, FP=97.914% y E_ff=93.06%).

Tepe Akım Kontrol Modunda Çalışan Flyback Dönüştürücünün Küçük Sinyal Ses Duyarlılık Analizi

Small signal audio susceptibility of flyback converter with peak current mode control method is presented by utilizing pwm-switch model in Continuous Conduction Mode (CCM). The analysis provides input voltage to output voltage transfer function together with its zeros and poles in symbolic form. Numerator and denominator of the resultant transfer function are both 3rd order. While symbolic equations of zeros are provided as exact solutions, the symbolic equations of poles are provided as approximate solutions with the assumption that the real pole is well separated from the resonant frequency of the complex pole pair. Symbolically derived transfer function of flyback converter is validated on a numerical example by time domain PSIM simulations on a switching flyback converter model. The mathematical analysis and PSIM simulations of input voltage to output voltage transfer function of the converter agree very well up to frequencies below half the switching frequency.

Tepe akım modu kontrollü Zeta dönüştürücünün küçük işaret analizi

In this study, small signal analysis of peak current-mode controlled, non-isolated Zeta converter is presented. The PWM-switch model in Continuous Conduction Mode (CCM) is utilized in the analysis. The control to output voltage transfer function is derived in symbolic form including the esr of the output capacitor. The exact zeros of the transfer function are given in symbolic form. However, the peak current-mode PWM-switch model yields 5 th order polynomial in its denominator, which necessitates approximate root analysis in finding the symbolic equations of its poles and quality factors. By using this analysis, the approximate poles and quality factors also derived symbolically in the paper. *

Modelling of nonisolated high-voltage gain boost converters using the PWM switch model

This paper presents the small-signal models for nonisolated dc–dc boost converters based on the three-state switching cell (3SSC) and voltage multiplier cells (VMCs) by using the concept of pulse-width modulation switch introduced by Vorpérian. Two possible topologies are analysed in the study using one multiplier cell (VMC = 1) and two multiplier cells (VMC = 2). The models are validated by properly comparing the theoretical curves with those obtained in simulation tests. Besides, conventional average current-mode control is implemented in practice for the topology with VMC = 2. An experimental prototype rated at 1 kW is evaluated so that it can be seen that the control system is stable and the dynamic response of the converter is satisfactory.

연료전지·이차전지 하이브리드 시스템을 위한 인터리빙 양방향 DC-DC 컨버터 설계

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

Modified PWM switch model for continuous conduction mode DC–DC converters with coupled inductors

A modified PWM switch model for DC-DC converters operating in continuous conduction mode (CCM) is proposed in this study. The modified model is based on the conventional PWM switch model. Compared to other modelling methods, the conventional model is versatile and easy to implement. However, it is typically restricted to a few topologies only. Therefore in this study, the proposed modified model expands the application fields, which includes the DC-DC converter with the coupled inductor; it can also be used in basic converters as a conventional topology. A high step-up buck-boost converter was built for this investigation to verify the accuracy of the modified model. The experimental results show that this modified model can accurately predict the characteristics of the system.

A new single-phase ZCS-PWM boost rectifier with high power factor and low conduction losses

This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching (ZVS) in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved because of the following reasons: 1) the circulating current for the soft switching flows only through the auxiliary circuit; 2) a minimum number of switching devices are involved in the circulating current path; and 3) the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Seven transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM-switch model is used to predict the system performance. A prototype rated at 1 kW, operating at 60 kHz, with an input alternating current voltage of 220 V/sub rms/ and an output voltage of 400 V/sub dc/, has been implemented in laboratory. An efficiency of 98.3% and a power factor over 0.99 have been measured. Analysis, design, and the control circuitry are also presented in this paper.

A new averaged switch model including conduction losses for PWM converters operating in discontinuous inductor current mode

In this paper a new PWM switch model including conduction losses, for Discontinuous Inductor Current Mode (DICM) dc-dc converters is developed. Compared to other models for DICM, the proposed model is more accurate, its derivation considering the correct, exponential waveforms for the currents and voltages. The proposed model is verified through PSpice simulation. A possibility of simplifying the model is also presented and verified through PSpice simulation.

Modeling of a single-switch quadratic buck converter

Ready-to-use nonlinear and linear averaged models for a single-switch quadratic buck converter are given. The nonlinear model is obtained from an averaged equivalent circuit model of the converter using the PWM-switch (pulsewidth modulation) model. The linear model is obtained by applying a small-signal perturbation to the corresponding averaged state-space description. The result shows that this quadratic converter exhibits the transfer characteristics of a fourth-order system. The resulting models are only valid in the continuous conduction mode (CCM). The validity of the proposed models was verified by computer simulation using PSPICE and MATLAB/SIMULINK for a specified converter. Experimental results on a prototype converter are also presented.

Improved ZCS-PWM commutation cell for IGBTs application

An improved zero-current-switching pulsewidth-modulated (ZCS-PWM) commutation cell is presented, which is suitable for high-power applications using insulated gate bipolar transistors (IGBTs) as the power switches. It provides ZCS operation for active switches and zero-voltage-switching (ZVS) operation for passive switches. Besides operating at constant frequency and reducing commutation losses, the proposed ZCS-PWM switch cell has no additional current stress and conduction loss in the main switch. To demonstrate the feasibility of the proposed ZCS-PWM commutation cell, it was applied to a boost converter. Operating principle, theoretical analysis, design guidelines, and a design example are described and verified by experiment results obtained from a prototype rated 1 kW and operating at 40 kHz. The PWM switch model and state-space averaging approach is also used to estimate and examine the steady-state and dynamic character of ZCS-PWM boost converter system. Finally, the application of the proposed soft-switching technique in the dc-dc nonisolated converters is presented.

An advanced PWM-switch model including semiconductor device nonlinearities

Contrary to the classical ideal averaged models, the introduced averaged model includes the nonlinear effects of the power semiconductor devices. The proposed nonideal pulse width modulated (PWM)-switch model is a useful method for modeling pulse width modulated converters operating in the continuous conduction mode. The main advantages of the proposed averaged model are that it takes into account the nonlinear effects of power devices and make it possible to estimate the dissipated power in the different circuit devices. The proposed model can be applied to bi-directional converters and allows the electrothermal simulations of the power electronic system. A simple technique to evaluate the different static and dynamic parameters of the devices, from manufacturers data sheets or experimentally, is presented.

Developing an advanced PWM-switch model including semiconductor device non-linearities

The accurate simulation of power electronic systems is possible when including accurate models of the semiconductor devices, but practically not affordable. Classical ideal averaged models of the system are not suitable either. Hence, averaged models including the non-linear effects of the power semiconductor devices appear quite efficient. The proposed non-ideal PWM-switch model is a useful method for modeling pulse width modulated converters operating in the continuous conduction mode. The main advantages of the proposed averaged model are the takes into account of the non-linear effects of power devices and the possibility to estimate the dissipated power in the different circuit devices. The proposed electrical model can be applied to bi-directional converters and allows the coupling with thermal model in the power electronic system. A simple technique to evaluate the different static and dynamic parameters of the devices, from manufacturers data sheets or experimentally, is presented.