Pulsewidth-modulated Switch Model Research Articles

Generalized Pulse Width Modulation Switch Model for Converters Based on the Multistate Switching Cell in Discontinuous Conduction Mode.

This work introduces a generalized version of the pulse width modulation (PWM) switch model applied in the small-signal modeling of converters based on the multistate switching cell (MSSC) operating in discontinuous conduction mode (DCM). It consists of extending the concept formerly introduced by Vorperian for the representation of multiphase converters in DCM, yielding a circuit-based approach that does not rely on matrix manipulations unlike state-space averaging (SSA). The derived dc and ac models are valid for any number of switching states and any operating region defined in terms of the duty cycle, thus allowing for determining the voltage gain and distinct transfer functions. A thorough discussion of results is presented to demonstrate the applicability of the derived models to represent distinct configurations of the MSSC.

Development of A Small-Signal Model for The DC-DC Buck Converter Based on The Three-State Switching Cell

This paper presents the small-signal modeling of a dc-dc buck converter based on the three-state switching cell (3SSC) using the PWM (pulse width modulation) switch model, which is a far simple approach if compared with other similar techniques e.g. average state-space modeling. The ac model is properly derived, which allows obtaining relevant transfer functions involving several variables. It is also shown that the Bode diagrams corresponding to the mathematical expressions obtained in the theoretical analysis are properly verified by simulation, being able to represent both operating conditions of the 3SSC i.e. nonoverlapping mode and overlapping mode. Finally, some results regarding the converter operation in voltage mode control are presented and discussed.

Bidirectional Power Flow Control in a DC Microgrid Through a Switched-Capacitor Cell Hybrid DC–DC Converter

This paper focuses on a bidirectional hybrid dc–dc converter suitable as an interface between two dc voltage buses in various applications including microgrids. The switched-capacitor cell, incorporated in the converter topology, gives the advantage of high voltage conversion ratio without using a transformer. This paper analyses the converter operation and the stability in the step-up and step-down operating modes through the state-space averaging method and through the pulse width modulation switch model method applied on an equivalent circuit model. The converter employs a current controller designed in frequency domain based on the Bode plot, using the K factor method. The simulation results obtained by means of an average and a detailed switching model prove, in good correspondence, that the controller is able to track the reference current waveform with good dynamic performance . Experimental results obtained from a 2 kW converter prototype confirm the theoretical considerations and the simulation results.

New family of zero-current-switching PWM converters using a new zero-current-switching PWM auxiliary circuit

A new family of zero-current-switching (ZCS) pulsewidth-modulation (PWM) converters using a new ZCS-PWM auxiliary circuit is presented in this paper. The main switch and auxiliary switch operate at ZCS turn-on and turn-off, and the all-passive semiconductor devices in the ZCS-PWM converters operate at zero-voltage-switching (ZVS) turn-on and turn-off. Besides operating at constant frequency and reducing commutation losses, these new converters have no additional current stress and conduction loss in the main switch in comparison to the hard-switching converter counterpart. The PWM switch model and state-space averaging approach is used to estimate and examine the steady-state and dynamic character of the system. The new family of ZCS-PWM converters is suitable for high-power applications using insulated gate bipolar transistors (IGBTs). The principle of operation, theoretical analysis, and experimental results of the new ZCS-PWM boost converter, rated 1.6 kW and operating at 30 kHz, are provided in this paper to verify the performance of this new family of converters.

Zero-current-transition PWM DC–DC converters using new zero-current-switching PWM switch cell

A new family of zero-current-switching (ZCS) pulsewidth-modulated (PWM) converters, which uses a new ZCS PWM switch cell, is presented. The main switch and auxiliary switch operate at zero-current-switching turn-on and turn-off, and the all passive semiconductor devices in the ZCS-PWM converter operate at zero-voltage-switching turn-on and turn-off. Besides operating at constant frequency and with reduced commutation losses, these new converters have no additional current stress in the main switch in comparison to the hard switching converter counterpart. The PWM switch model and state-space averaging approach is used to estimate and examine the steady-state and dynamic character of system. The new family of ZCS-PWM converters is suitable for high-power application using insulated gate bipolar transistors. The principle of operation, theoretical analysis and experimental results of the new ZCS-PWM boost converter, rated at 1 kW and operating at 30 kHz, are provided to verify the performance of this new family of converters.

A New Family of Zero-Current-Switching (ZCS) PWM Converters

A new family of zero-current-switching (ZCS) pulsewidth-modulated (PWM) converters which uses a new ZCS-PWM switch cell is presented in this paper. The main switch and auxiliary switch operate at ZCS turn-on and turn-off, and all the passive semiconductor devices in the ZCS-PWM converter operate at zero-voltage-switching (ZVS) turn-on and turn-off. Besides operating at constant frequency and with reduced commutation losses, these new converters have no additional current stress in comparison to the hard-switching converter counterpart. The new family of ZCS-PWM converters is suitable for high-power applications using insulated gate bipolar transistors (IGBTs). The PWM switch model and state-space averaging approach is used to estimate and examine the steady-state and dynamic character of the system. The principle of operation, theoretical analysis, and experimental results of the new ZCS-PWM boost converter, rated 1 kW and operating at 30 kHz, are provided in this paper to verify the performance of this new family of converters.

A Novel ZCS-PWM Power-Factor Preregulator With Reduced 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 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, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and 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. Nine 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 50 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.3% and power factor over 0.99 has been measured. Analysis, design, and the control circuitry are also presented in this paper.

ZCS-PWM boost rectifier with highpower factor andlow conduction losses

A new single-phase high power factor rectifier is proposed, 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 switches and zero-voltage-switching (ZVS) in the diodes. 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, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and 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 60 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.2% and power factor near 0.99 has been measured. The analysis and design of the control circuitry are also presented.

Alternate forms of the PWM switch model in discontinuous conduction mode [DC-DC converters

A pulsewidth-modulated (PWM) DC-DC converter enters discontinuous conduction mode (DCM) as its inductor current attempts to reverse direction, but cannot do so because of switch implementation, and remains at zero in the last interval of each switching period. Three equivalent three-terminal nonlinear transformers are described as the models for the PWM switch in a DCM converter, each having one of the three terminals serving as the common terminal. Each model facilitates the analysis of those corresponding converters in which the PWM switch terminal corresponds to the common transformer terminal is DC-grounded. Examples are given to demonstrate how the models are used to derive the DCM criteria, and the ideal and nonideal voltage gains for the buck-boost, buck, and boost DC-DC converters. The results predicted by the models agree with those reported and verified in the literature.

Novel reduced-order small-signal model of a three-phase PWM rectifier and its application in control design and system analysis

A reduced-order (RO) small-signal model of three-phase pulse-width-modulation (PWM) rectifiers is proposed. By combining the PWM switch model and equivalent multimodule model techniques in DC-DC converters, a three-phase rectifier can be modeled as a DC-DC converter with equivalent power capability and small-signal characteristics. This model reduces the system order to two and greatly simplifies the control design and system analysis of three-phase converters. In this paper, the proposed model is also used for control design and for system interaction analysis on the three-phase interface of a boost rectifier. The RO model is verified with the d-q model, switching-model simulation, and experimental results.

Comparison of performance of single-loop and current-injection control for PWM converters that operate in both continuous and discontinuous modes of operation

A comparison of single-loop and current-mode controlled power converters operating in the continuous and discontinuous modes is performed using the PWM (pulse width modulation) switch model and a new, continuous-time model of current injection control (CIC). The theoretical and experimental results show a significant performance improvement that can be realized when CIC is employed in converters which operate over a wide load range. Except for the single-loop, continuous mode transient response time, all the CIC figures are equal to or better than the single-loop figures. The transient response time of CIC can be improved to be equal to or better than single-loop control by placing the compensation zero at a higher frequency. The penalty is that the system loop gain will be conditionally stable. This may not be significant, though, since the system loop gain crossover frequency is governed by the current loop. The current loop is determined by the external ramp slope. >