Discontinuous Conduction Mode Operation 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.

Lyapunov stability analysis and FIL implementation for boundary‐based hybrid controller in boost converter

AbstractThis paper presents a comprehensive stability analysis of the boundary‐based hybrid control (BBHC) algorithm designed for boost converter. The stability assessment is carried out utilizing multiple Lyapunov functions, addressing both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) operation. The boost converter is modeled as a hybrid automaton to capture its dynamic behavior accurately. Through rigorous Lyapunov stability analysis, this study demonstrates the effectiveness of the BBHC algorithm in ensuring stable operation of the boost converter across various operating modes. Additionally, the proposed control algorithm's validation is conducted using the FPGA‐in‐the‐loop (FIL) technique, highlighting its efficiency and robustness in real‐world applications. This research contributes valuable insights into the design and implementation of stable control strategies for boost converter, emphasizing the practical utility of the BBHC algorithm with FIL for enhanced performance and reliability in power electronics systems.

Power Loss and Temperature Distribution in Coil of PFC Inductor with Air Gap for Multimode Operation

Power converters inherently display non-linear load characteristics, resulting in a high level of mains harmonics, and hence the necessity of implementing Power Factor Correction (PFC). Active PFC circuitry typically comprises an inductor and a power switch to control and alter the input current so that it matches, in shape and phase, the input voltage. This modelling of the waveforms can be performed by means of distinct conduction modes of the PFC inductor. The digital controller implemented in the constructed and investigated boost-type PFC converter can be programmed to operate in discontinuous conduction mode (DCM), continuous conduction mode (CCM), or a combination of the two. The individual modes of operation, via distinct PFC inductor current waveforms, impact the overall efficiency of power conversion and, by extension, temperature distribution in the magnetic component. This paper investigates how the examined conduction modes bear on distinct power-loss mechanisms present in the PFC inductor, including high-frequency eddy-current-generating phenomena, and the fringing effect in particular. As demonstrated herein, the DCM operation, for the set output power level, exhibits exacerbated power dissipation in the winding of the inductor due to the somewhat increased RSM value of the current and the intensified fringing magnetic flux at an air gap. The latter assertion will undergo further, more quantitatively focused research. Finally, the construction of the coil was optimised to reduce power loss by diminishing eddy-current mechanisms.

Differences between Riemann–Liouville and Caputo calculus definitions in analyzing fractional boost converter with discontinuous‐conduction‐mode operation

SummaryFractional‐order calculus is an extension of the integer‐order calculus in that its order is not limited to integers but can be noninteger as well, thus making the application of fractional‐order calculus more flexible. It has been shown that actual reactive elements such as capacitors and inductors have fractional‐order properties and that the theory of fractional‐order calculus can be utilized to more accurately characterize circuits and systems containing reactive elements. However, there is no uniform definition of fractional order calculus. Different definitions will yield different results in solving the same fractional‐order circuits and systems, and it is worth exploring whether these differences have an impact on the accuracy of solving fractional‐order systems. Taking a fractional‐order boost converter running in discontinuous conduction mode (DCM) as an example, this paper focuses on the differences between the Riemann–Liouville (R–L) and the Caputo fractional calculus definitions. Effects of the two definitions on the division of the converter's CCM (continuous conduction mode) and DCM operating regions are analyzed, as well as their impact on the characterization of a fractional‐order boost converter in DCM operation, including the DC (direct current) operating point, current ripple, and voltage gain. Simulations and experiments show that the analytical results based on the R–L definition can more accurately describe the operation of a real fractional‐order converter than those based on the Caputo definition.

Performance analysis of a bridgeless power factor correction (PFC) buck–boost LED driver with ripple diversion scheme for extended lifespan

SummaryIn the state of the art of AC‐fed light‐emitting diode (LED) drivers, power factor correction (PFC), second harmonic LED current ripple elimination, low current total harmonic distortion (iTHD), removal of electrolytic capacitors (EC) and flicker‐free operation are the major challenging issues. This paper proposes a bridgeless universal voltagerange AC‐fed LED driver that overcome the major issues of LED driver. The bridgeless buck–boost PFC configuration minimizes the losses relative to the front‐end bridge rectifier‐based configurations. Operating in discontinuous conduction mode (DCM), the source current tracks the input voltage shape for a wide operating range, achieves inherent PFC and maintains low input current THD. Also, this provides significant reduction in the output current ripple with the ripple diversion circuit (RDC) connected in shunt across the LED load, which relatively reduces and utilizes low value of output capacitance. Hence, a flicker‐free operation is achieved without the use of electrolytic capacitors. In addition, the elimination of ECs improves the operating lifespan of the proposed LED driver. A detailed theoretical analysis and results of the proposed LED driver are validated on DSP and analog controller platforms with a 62 W/62 V experimental laboratory prototype. The experimental results confirm that the proposed LED driver achieves a power factor of 0.94–0.997, input current THD of maximum 6.8%, output current ripple of 5%, and a peak efficiency of 91.25% for the wide range of input voltage variation. These indices also satisfy IEC‐61000‐3‐2 and IEEE 1789‐2015 standard limits.

Single-Phase Voltage-Doubler High-Power-Factor Ćuk Rectifier Operating in Discontinuous Conduction Mode

Single-Phase Voltage-Doubler High-Power-Factor Ćuk Rectifier Operating in Discontinuous Conduction Mode

Unified small‐signal model for DC‐DC converters based on the three‐state switching cell operating in discontinuous conduction mode

SummaryUnified small‐signal modeling approaches are of paramount importance for the design of controllers and closed‐loop control systems in power electronic converters. In this sense, this work proposes the small‐signal analysis of non‐isolated dc‐dc converters employing the three‐state switching cell (3SSC) in discontinuous conduction mode (DCM). The modeling technique relies on the very same principles of the pulse width modulation (PWM) switch while not involving matrix operations, but only basic concepts related to electric circuits. Considering that the waveforms associated with the terminals of the 3SSC in DCM have a common behavior in all basic dc‐dc converters, it is possible to derive the small‐signal models for both operating regions of the 3SSC, that is, non‐overlapping mode (NOM) and overlapping mode (OM). Thus, one can effectively demonstrate that the same circuit can represent both modes, even though the coefficients that describe the models are calculated from distinct equations. The theoretical claims are validated in the frequency and time domains while comparing the model with the converter. The obtained results evidence that the unified model can accurately represent converters based on the 3SSC in DCM.

Preliminary design of an OWC wave energy converter battery charger

This paper introduces a low-power off-grid oscillating water column wave energy converter with an internal battery bank. The research aims at the preliminary design and devising of the control strategy of a power electronics interface between the turbo generator and the battery bank. The converter comprises a spar buoy, a biradial turbine, a permanent magnet generator, a full-wave bridge rectifier, a braking chopper, a DC-to-DC step-down converter, and a lead-acid battery bank. The power-take-off system was modelled in Simulink/MATLAB, and its performance was assessed with steady-state simulations, considering a wave climate characteristic of Leixões, Portugal. The chamber pressure, the turbine, generator and rectifier performance were taken from experimental data sets. A simple battery model was derived from the manufacturer's datasheet. An ideal step-down DC-to-DC converter operating in discontinuous conduction mode regulates the battery charging current. This converter, in parallel with the braking chopper, adjusts the generator counter torque by regulating the current through the rectifier. Twelve system variables were recorded for selected pairs of input pressure and step-down converter design coefficient. The power at the rectifier's output terminals was mapped for the rotational speed and input pressure. The results show a system rating of 1.4 kW with 400 W of electrical power at 200 rad/s for the most frequent sea states. The range of the duty cycle, the inductance and the braking resistance were derived. Two closed-loop controllers were proposed for managing the step-down converter and the braking chopper. Their set points and saturation limits were derived from the simulation results.

A Three-Phase Phase-Modular Single-Ended Primary-Inductance Converter Rectifier Operating in Discontinuous Conduction Mode for Small-Scale Wind Turbine Applications

Small-scale wind turbines play an important role in distributed generation since customers can use their houses, farms, and business to produce electric energy. The development of the power electronics system that processes the electric energy from small-scale wind turbines is a concern due to cost, simplicity, efficiency, and performance trade-offs. This paper presents the results of applying a three-phase phase-modular single-ended primary-inductance converter rectifier to processing the energy of a small-scale wind turbine system. The rectifier was designed according to the specifications of a commercial small-scale wind turbine system and tested in an emulator workbench, providing experimental data on the operation of the rectifier in this application. The rectifier can process the energy of a non-sinusoidal three-phase system since the permanent magnet synchronous generator has trapezoidal waveforms. The results show that the rectifier has the advantages of (i) using the inductance of the generator as the input filter inductor of the rectifier, (ii) providing input currents with the same shape as the voltages and in phase without the use of a current control system, (iii) simplicity of control of the DC output voltage and PWM modulation, and (iv) phase-modular characteristics that allow operating with phase fault without any additional control techniques. Due to the operation in discontinuous conduction mode, low efficiency in high power and/or low input voltage specifications are disadvantages.

GaN-Based Isolated Resonant Converter as a Backup Power Supply in Automotive Subnets

This paper presents the analysis, design and implementation of a 2 MHz, 12 V, 600 mA, GaN-based Active-Clamped Isolated SEPIC Converter (ACISC) supporting full Zero-Voltage Switching (ZVS) throughout the 9 V-18 V automotive range, and intended to provide isolation and power interface between the 12 V battery and the low-power subnet. Designed for resonant Discontinuous Conduction Mode (DCM) operation and leveraging the high switching frequency enabled by Gallium Nitride (GaN) devices, the selected topology leads to a reduction in total magnetic size and footprint, while maintaining a high efficiency profile. Both the theoretical model specifically developed for full ZVS resonant DCM operation, as well as the design and implementation of the transformer, are discussed. The analysis was verified through simulations and experimental measurements taken on a 7.2 W GaN-based prototype employing a planar transformer. Performance comparison with both a 7.2 W GaN-based Active-Clamped Isolated Flyback Converter (ACIFC) and a commercial Flyback converter is also included.

Discontinuous conduction mode approach of ultra-lift DC-DC converter based on three windings coupled inductor

These days, DC-DC boost converters play an essential role in a variety of applications. Therefore, a variety of techniques were proposed in the literature to achieve the highest voltage gain. A large number of passive elements are typically used in high-voltage DC-DC converters. Increasing the order of the system would make modeling and controlling the output voltage of the converter more complex. This paper examines an ultra-lift DC–DC converter using a three-winding inductor and a super-lift construction in discontinuous conduction mode (DCM). This converter provides substantial voltage gain by utilizing the three-winding coupling inductor topology without increasing the duty cycle or passive circuit parts. Because the DCM operation mode occurs in the converter, it is necessary to investigate and analyze it. The DCM operation mode of an Ultra-Lift converter is examined in this study, and then simulation results are shown to validate the equations.

Time-Domain Analysis and Optimal Design of LLC-DC Transformers (LLC-DCXs) Considering Discontinuous Conduction Modes

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DC transformers ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCXs) operate under fixed-frequency and open-loop conditions to achieve high efficiency and are promising converters that can be used in the auxiliary power units (APUs) of electric locomotives. An optimal design method of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCXs is proposed in this paper. First, the time-domain expressions of the symmetric half-bridge <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with split resonant capacitors are derived. A current increment method is proposed to determine the expressions. Second, the discontinuous conduction mode (DCM) and voltage gain limiting conditions are used to obtain the magnetizing inductance ranges. The converter losses and zero-voltage-switching (ZVS) ranges are considered to determine the final magnetizing inductance. A 10 kW prototype is used as an example, and a detailed parameter design process is implemented. Compared with conventional design methods for the magnetizing inductance, the proposed method can effectively determine the maximum magnetizing inductance for the DCM operation of the converter. The effectiveness of the proposed method is proven by the simulations and experimental results obtained for the 10 kW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCX prototype. The maximum efficiency of the designed converter is 98.12% under the full load.

A Unified Analysis of DC–DC Converters’ Current Stress

There is always a need to analyze current signals generated by various DC–DC converters. For example, to determine the current stress experienced by semiconductor devices and to evaluate active and reactive power consumption in converters. The study demonstrates that the shape of a current signal dictates the analytical expressions required to determine the average and RMS values of a signal as well as the RMS value of the ripple of that signal. The study also shows that current signals can be treated as composite waveforms comprising various combinations of trapezoidal, rectangular, and triangular pulses. The current literature lacks a unified approach to analyze current stresses in DC–DC converters. This study will propose a unified and generalized analytical technique that is applicable to any type of DC waveform that can be treated as a composite waveform made up of a combination of triangular, rectangular, or trapezoidal sections or sub-intervals. Furthermore, the rectangular and triangular pulses are shown to be a special kind of trapezoidal pulse. This provides the basis for a very broad generalization of current signals’ analysis based on the analysis of a trapezoidal pulse. Additionally, a method for the direct evaluation of signals’ ripple RMS content is developed. This is unlike in the current literature where it is necessary to evaluate the signal’s average and RMS values before ripple content can be evaluated. The technique developed is applicable to continuous and discontinuous conduction modes of operation.

Boundary-Based Hybrid Control Algorithm for Switched Boost Converter Operating in CCM and DCM

It is essential to have enhanced efficiency for the DC-DC converters operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). This requires a hybrid controller designed using pulse width modulation (PWM) and pulse frequency modulation (PFM) schemes. This paper fixates on a boundary-based hybrid control algorithm for the second-order DC-DC converter - the switched boost converter. The proposed algorithm works in PWM control scheme for CCM operation, whereas DCM operation uses PFM control scheme. The boundary conditions are defined by the load current, output voltage, and switching frequency. Here, an attempt is carried out to have the advantages of both the control schemes. The boost converter is represented by the switched system operating in three modes. Violating transition guards condition orchestrates the switching among these modes. A supervisor detects the CCM and DCM operations, and subsequently switches between PWM and PFM control scheme. Extensive circuit-level simulations are carried out in MATLAB to show the efficacy of the suggested algorithm under the fluctuating line, load, and set-point.

In-Depth Analysis of Smooth and Nonsmooth Bifurcations for an Open-Loop Boost Converter Feeding Constant Power Loads in Discontinuous Conduction Mode

This paper presents a study of the existence conditions of limit cycles and mechanisms when losing their stability in an open-loop DC–DC boost converter loaded with a constant power load and operating in discontinuous conduction mode. First, the existence conditions are determined. Then, boundaries associated with different kinds of instabilities such as the classical smooth fold and period-doubling bifurcations and nonsmooth border-collision bifurcations such as fold border-collision bifurcations are elucidated. To perform the stability analysis, an implicit 1D map for the system is derived. From this model, it is obtained that smooth period-doubling and fold bifurcations may occur at certain values of the circuit parameters. Some results from numerical simulations performed on the circuit-based switched model are provided showing consistency with the theoretical analysis from the derived model.

A Dual-Input Single-Output DC-DC Converter Topology for Renewable Energy Applications

Multi-port power converters are widely used in managing multiple energy sources and loads. To that end, a dual-input single-output dc-dc converter is proposed in this article. The converter integrates two low-voltage dc sources into a dc bus. Pulse width modulation is used to control the transfer energy from the input ports to the output port. The soft-switching operation in the primary side switches is achieved with the help of the secondary side modulation and the discontinuous conduction mode (DCM) operation of the primary inductors. Moreover, the DCM operation helps avoid the high-frequency transformer saturation even when the two input voltages have different magnitudes. Detailed analysis of the proposed dc-dc converter is presented in this article. The steady-state operation, the dynamic performance at the output load variation and input voltage disturbances, and maximum power point operation of the converter are validated through the simulation and experimental results obtained from a 200 W hardware prototype.

Fuzzy Control of a High-Performance Boost Converter in Discontinuous Conduction Mode and its Application to a Photovoltaic Pumping System

In this work, a fuzzy voltage controller design of a 1 kW high-gain, high-efficiency direct current converter operating in discontinuous conduction mode is developed. In this condition, the design of a conventional controller is more challenging. This converter is part of an autonomous photovoltaic pumping system without batteries consisting of four photovoltaic modules, a variable frequency inverter and an induction motor coupled to a pump. The boost converter is responsible for the voltage elevation of photovoltaic modules to a 311V direct current bus, which must not have oscillations for a good operation of an algorithm to track the maximum power point of the modules. The fuzzy controller was implemented in a digital signal processor device to control the boost converter, producing a response with an overshoot of 5.78%, settling time of 3.8s and zero error in steady state.

Bifurcation Phenomena in Open-Loop DCM-Operated DC–DC Switching Converters Feeding Constant Power Loads

Constant power loading is an effect that appears in multiple-stage energy conversion systems with individually regulated switching power converters. In a two-stage system, an upstream or source converter drives one or more downstream or load converters. The downstream converters in a two-stage power conversion system are designed to provide the fastest transient response in stand-alone operation. Consequently, they behave as a constant power load (CPL) to the upstream converter within their control bandwidth. In the past, open-loop power converters feeding CPLs and operating in discontinuous conduction mode (DCM) were considered to be stable. In this paper, it is shown that these systems can undergo instabilities, which have been so far overlooked. First, numerical simulations from the switched model of an open-loop boost converter under DCM operation and loaded with a tightly regulated buck converter and the same converter loaded by an ideal CPL are presented to show that they exhibit similar nonlinear behavior and bifurcation phenomena. Then, the three elementary open-loop DC–DC converters operating in the DCM were considered and their bifurcation phenomena were revealed. It is shown that the period-doubling route to chaos in the DC–DC boost converter is interrupted by a sudden appearance of dangerous destructive dynamics due to the excessively unlimited load current in the CPL. For the buck converter, only the first period-doubling bifurcation is observed before the destructive behavior appears. The open-loop buck–boost converter under DCM and feeding a CPL is always unstable and exhibits no periodic orbit. Based on the observed phenomena, approximate discrete-time models were derived, which despite their simplicity, were seen to display the most-important and -essential features of the corresponding switching converters before destructive dynamics occurs.

A Novel Single Phase Grid Connected Transformer-Less Solar Micro-Inverter Topology With Power Decoupling Capability

A novel transformer-less micro-inverter topology suitable for interfacing a 35 V, 220 W solar PV module to a single phase 220–230 V ac grid is proposed in this paper. It employs only six switches, out of which two switches operate at high frequency, three at line frequency and one switch at high frequency during the negative half cycle of the grid voltage. The micro-inverter is operated in discontinuous conduction mode of operation for all possible operating conditions to achieve high gain as well as negligible turn on losses for the high frequency switches. In this topology the negative terminal of the PV module is shorted with the grid neutral which makes the magnitude of the leakage current flow to be zero. The power decoupling between the dc and ac sides is inherent in this topology, and it is achieved without incorporating any active power decoupling circuit. Thin film capacitors are utilized to improve the reliability of the micro-inverter. The detailed analyses of the proposed micro-inverter are carried out. The effectiveness of the proposed scheme is verified by performing detailed simulation studies. A 220 W laboratory prototype of the proposed micro-inverter is fabricated, and detailed experimental studies are carried out to confirm the viability of the proposed scheme.

Online DC-Link Capacitance Monitoring for Digital-Controlled Boost PFC Converters Without Additional Sampling Devices

Aluminum electrolytic capacitors (Al-Caps) are widely used in the dc link of ac/dc applications; however, they are one of the weakest components in power electronic converters. With the degradation of Al-Cap, its capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> ) decreases, and the equivalent series resistance increases. Based on this, many efforts have been made to realize condition monitoring (CM) of Al-Caps. Unfortunately, additional hardware (including current sensors and sampling circuits) and/or powerful data processing tools are usually required, which increases the cost and would bring new reliability risks. Considering this issue, this article presents a transient-based CM scheme for dc-link capacitors in digital-controlled boost power factor correction (PFC) converters, which does not need additional sampling devices. By analyzing the relationship between large-signal transient voltage profile and dc-link capacitance, a calculation model is established. Based on the sampled voltage and current signals used for digital control, the dc-link capacitance can be online estimated. Its feasibility is validated in simulation with a boost PFC operating in continuous conduction mode (CCM) and discontinuous conduction mode. Furthermore, taking a 1-kW boost PFC operating in CCM as a case study, experimental results illustrate that the estimation errors of the dc-link capacitance are less than 3.5% (error of a single test) and 1.5% (average error of multiple tests).