Asymmetrical Duty Research Articles

Dual-Side Asymmetric Duty Modulation Based on Accurate Soft-Switching Characteristics Modeling for DAB-Based DC Microgrid

Dual-Side Asymmetric Duty Modulation Based on Accurate Soft-Switching Characteristics Modeling for DAB-Based DC Microgrid

Multioutput Wireless Charger for Drone Swarms With Reduced Switch Requirements and Independent Regulation Capability

This paper develops a cost-effective and efficient wireless charger with multiple outputs based on newly proposed H3 bridge inverter, which has the benefits of reduced switch requirements and independent regulation capability. The output power of each channel is regulated by asymmetric duty cycle control. With the help of auxiliary LC branch, soft switching is ensured in spite of load variations. The sequential logic of driver signals is analyzed in detail to explore the independent regulation characteristic. For arbitrary 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> (or 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> +1) outputs, the total number of required switches is only 3 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> (or 3 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> +2) and the voltage stress of switches is the input voltage, which can reduce switch requirements. Simulation and experimental results are in good agreement with each other, proving the proposed wireless charger as a feasible solution for drone swarms.

A Two-Phase Interleaved Bidirectional DC-DC Converter With Asymmetrical Duty Limit Control for Wide-Range DC-Bus Voltage Applications

A Two-Phase Interleaved Bidirectional DC-DC Converter With Asymmetrical Duty Limit Control for Wide-Range DC-Bus Voltage Applications

Primary side control strategies for battery charging regulation in wireless power transfer systems for EV applications

AbstractResonant inductive‐based wireless power transfer (WPT) for battery charging has potential applications in electric vehicles (EVs). The EV battery charging process requires the regulation of both charging voltage and current. Duty ratio or frequency control is generally preferred to manage the power flow between the transmitter and receiver coils in the WPT system. In the case of WPT charging, misalignment between the coils and parameter variations are unavoidable issues that result in changes to the output power. Therefore, it is essential to control the power flow to maintain constant current (CC) and constant voltage (CV) modes during battery charging. To address these challenges, various primary‐side control techniques, such as asymmetric clamped mode (ACM), asymmetric duty cycle (ADC), and phase‐shift (PS) fixed frequency control strategies, have been proposed for WPT systems. This paper conducts a comparative analysis of these control methods, considering their output voltage ranges and their ability to maintain zero‐voltage switching (ZVS) for the entire control range. Furthermore, the paper presents a generalized design for reduced‐order small signal modelling, utilizing an extended describing function. The designed controller, based on small signal modelling, will undergo real‐time testing to evaluate its dynamic performance in the series‐series resonant converter.

Fault Current Control of Three-Phase Dual Active Bridge DC–DC Converter Employing Modified Asymmetrical Duty Cycle Control Modulation

Fault Current Control of Three-Phase Dual Active Bridge DC–DC Converter Employing Modified Asymmetrical Duty Cycle Control Modulation

Optimal Asymmetric Duty Modulation for Dual Active Bridge Converters with DC Blocking Capacitors

Aiming at the optimization of current stress with low voltage ratio and full ZVS, a control method combining variable duty cycle and phase shift was proposed based on dual active bridge (DAB) converters with DC blocking capacitors. By adding DC bias to the DC blocking capacitors, asymmetric duty modulation (ADM) can adjust the bias as needed. Based on the theoretical analysis of steady-state operation, the operating modes can be divided into eight modes. According to the features of each mode, equivalent circuits are established. The transmission power and the boundary of zero-voltage-switching (ZVS) are deduced through a detailed analysis of each mode. Based on the theoretical deduction, ADM is more suitable for a low voltage ratio. Verified by experiment, optimized asymmetric duty modulation (OADM) can increase efficiency by 3.58%, 6.57%, 8.81%, and 10.33% compared with DPS when P is equal to 0.36 and m is equal to 0.4, 0.3, 0.2, and 0.1, respectively. Using this method, the current stress of the converter is lighter than that under regular modulation when the voltage ratio m ≤ 0.5 with full ZVS.

Review of Modeling, Modulation, and Control Strategies for the Dual-Active-Bridge DC/DC Converter

This paper provides a comprehensive review of the existing research on the Dual Active Bridge (DAB) DC-DC converter, focusing on modeling methods, modulation strategies, optimization algorithms, and control methods. A comparative analysis of selected methods along with guidelines to assist engineers and researchers in their study of DAB is also presented. Firstly, a comprehensive review of modulation strategies for DAB is provided, ranging from classical phase-shift modulation to the popular asymmetric duty modulation. The intrinsic relationships among different modulation methods are summarized, and a comparison is made based on the difficulty of control and DAB operating characteristics. Secondly, the various modeling methods for DAB are described, including reduced-order modeling, generalized state-space averaging modeling, and discrete-time modeling methods. A comparison is made based on the suitability for different application scenarios, providing recommendations for the adoption of different modeling methods. Furthermore, a survey of optimization algorithms for modulation methods is presented, including classical algorithms, swarm intelligence optimization, and reinforcement learning algorithms. A number of criteria are proposed for different algorithms, and an analysis of the unresolved challenges and future prospects is provided. Finally, the advanced control methods for DAB are summarized based on control effectiveness and applicability. The article concludes with a summary and an outlook on future research directions is also provided.

An Independently Controlled Two Output Half Bridge Resonant LED Driver

In this research work, an independently controlled two output half-bridge resonant LED driver is proposed. Half bridge series converters will be providing power to two LED lamps. The devices in half-bridge converter are switched at zero voltage using LC resonant circuit. Therefore, switching transition power losses are minimized which increases the LED driver efficiency. Each LED lamp’s ripple current is decreased by adding an inductor in series with it, eliminating the need for an electrolytic capacitor and extending the life of the resonant LED driver. Both regulating and dimming operations use asymmetrical duty cycle (ADC) control. Numerical simulations are conducted to examine the suggested resonant converter topology’s steady state performance as it sources LED applications. Using the OrCAD/PSPICE tool for universal AC mains, 25 W and 29 W LED driver analysis, design, modeling, and simulation are carried out. The proposed driver needs to provide high efficiency even at reduced illumination.

Compensation of the Current Imbalance of an Interleaved DC–DC Buck Converter, Sensorless Online Solution Based on Offline Fuzzy Identification and Post-Linearization

This paper presents a new approach to compensate for the current imbalance of an interleaved DC–DC buck converter (IBC), in which the current sensors are not involved in the operation of the converter when it is connected to an invariable load. The current sensors are only used during the offline identification process that builds the universal fuzzy model of the converter’s steady states. Model building involves an upstream identification phase, followed by further dimensionality reduction of the model and error minimization. The method presented here discusses the mathematical complexity of the analytical modelling of hybrid systems and opposes it with a complexity-reduced identification by learning from data. An offline rendered model of the stable and steady states of the IBC is used as a mapping of the required inverter output current to n-fold asymmetric duty cycles, which are distributed among the IBC phases to allow arbitrarily accurate load sharing. The mapping is carried out in the mathematically normalized space of variables or in the physical sense RMS values, achieving the desired robustness in a noisy environment and stability. The final and canonical feedback control is built from the standard and optimized PI controller, which is compensated by the identified IBC model correction. The only measured feedback of the whole controller is the output voltage. Even when applied to the simulation model (physical MATLAB platform) of a two-phase IBC with the built-in system asymmetry, the presented methodology is also applicable to the n-phase IBC without loss of generality.

Proposed asymmetric phase shift modulation strategy to improve zero-voltage-switch range and transmission power range for dual active bridge converter

The dual active bridge (DAB) DC–DC converter is typical in DC transformers to realize the voltage transformation and power transmission, which is determined by modulation. However, in traditional phase shift modulation strategies, the zero-voltage-switch (ZVS) range and the transmission power range of DAB are limited, and the current bias exists in light load. Therefore, a proposed asymmetric phase shift modulation strategy (PAPSM) to realize full ZVS range, larger transmission power, and non-DC bias in high frequency link (HFL) for DAB is introduced in this paper. In PAPSM, the modulation signals in adjacent periods are symmetric and in the opposite direction, and the current characteristics in the adjacent periods are still consistent. Thus, the equivalent period of DAB in PAPSM is expended, and the current bias accumulation in light load is eliminated in the equivalent period, without any extra operation. Then, the operating principles of DAB in PAPSM are introduced, to analyze the ZVS range, power delivery range, and maximum transmission power in detail. Compared with traditional phase shift modulation strategies, PAPSM can realize full ZVS range, wider power delivery range, and larger maximum transmission power by adjusting an outer phase shift ratio and an asymmetric duty ratio, and the DC bias in HFL can be eliminated. Finally, a DAB experimental setup is established based on RT-LAB, proving the theoretical analysis.

Correction: Novel asymmetric duty modulation for DAB converters to improve light load efficiency

Correction: Novel asymmetric duty modulation for DAB converters to improve light load efficiency

Dual Output and Dual-Frequency Resonant Inverter-based Induction Heating Using ADC Control

A dual output dual-frequency (DODF) resonant converter-based AC-AC induction heating (IH) by using asymmetrical duty cycle (ADC) control is presented in this paper. The proposed scheme gives two outputs with independent power control, which improves input power factor and achieves zero voltage switching (ZVS) with a wide range of operations. It includes two pairs of two half-bridge series resonant converters, each pair having one common capacitor along with various resonant frequencies. These converters are modulated with the ADC control scheme to obtain smooth operation. The proposed topology doesn’t use the DC stage; it is directly connected to the power supply to produce high-frequency AC output. With the use of direct connection, the converter components are reduced when compared to conventional converters. There will be a reduction in voltage drop, power losses, cost of the converter and which will result in improved efficiency. Simulation results are obtained from PSIM 11.1.7 software. This scheme controls two different loads with an efficiency of 98.25%.

Backflow Power Optimization of DAB Based on Asymmetric Duty Cycle and Internal Phase Shift Control

Dual active bridge (DAB) converter with single-phase-shifting (SPS) control would produce large backflow power when voltage regulation ratio deviates from 1 or under light load, an asymmetric duty cycle and internal phase shift (ADIPS) control was proposed which controls the transmission power by duty cycle and internal phase-shift ratio and the backflow power can be eliminated under light load therefore improves the efficiency of DAB converter. By establishing mathematical models of inductor current and transmission power, the working principle of the proposed control method was given as well as the cause of backflow power was analyzed. The constraints of zero backflow power and an optimization control method of zero backflow power under ADIPS control was presented. At last, an experimental prototype is used to obtain the validation results, simulation and experimental results verify the excellent performance of the proposed control strategy in eliminating the backflow power of DAB converter under light load.

Novel asymmetric duty modulation for DAB converters to improve light load efficiency

Novel asymmetric duty modulation for DAB converters to improve light load efficiency

A Three Switch Resonant Inverter for Multiple Load Induction Heating Applications

Induction heating (IH) is a trending technology in the domestic applications due to its advantages related to high efficiency, better control, and fast heating. Present research focuses on developing cost-effective and highly efficient solutions. In this article, a three-switch inverter (3SI) for multiple load IH applications is proposed, which meets previous requirements. Reduced component count and high efficiency are the key benefits of the proposed inverter. Asymmetric duty cycle control is used to obtain independent control over two loads simultaneously. The operation of the proposed 3SI has been verified by rigorous simulations in Orcad PSpice software and by experimenting with designed hardware prototype. The simulation and experimental results are in good agreement with each other, proving the proposed 3SI as a feasible solution for multiple load IH applications.

Research on Efficient Single-Sided Asymmetric Modulation Strategy for Dual Active Bridge Converters in Wide Voltage Range

For the problem of narrow soft-switching range and low efficiency of dual active bridge (DAB) converter in wide voltage range, this article proposes a single-sided asymmetric duty modulation (SSADM) strategy, which contains only two control degrees of freedom, and significantly improves the soft-switching performance and efficiency at light load. First, the potential advantages of asymmetric duty modulation (ADM) method are described through waveforms. The principle of determining which full bridge to adopt the ADM is given and the working principle of SSADM is described. Second, a linear pulse logic combination analysis of SSADM in time domain is performed to establish a complete steady-state mathematical model. To solve the analytical expression for the optimal solution of SSADM, the peak-to-peak value of the inductor current with simple expression is chosen as the optimization objective, and the global optimal solution of SSADM is solved based on the Karush–Kuhn–Tucker (KKT) condition, and the voltage closed-loop control strategy of SSADM is presented. In addition, the soft-switching range of SSADM is analyzed. Finally, the experimental platform of DAB converter based on SiC device is built. Compared with other modulation strategies, SSADM shows better soft-switching performance with significant efficiency improvement, which is verified by the experimental results.

Comprehensive Analysis of Asymmetric Modulated Dual-Active-Bridge Converter and Its Hybrid Control Strategy

Dual active bridge (DAB) converter has been widely used in distributed power supply, new energy vehicles, energy storage systems, etc. Their modulation strategy is an important research direction. At present, the research on modulation strategy is basically symmetric phase shift, but it is not enough to generalize modulation strategy comprehensively. In this article, an asymmetric phase-shifting (APS) strategy is proposed to control the power flow by simultaneously adjusting the asymmetric duty cycle and the phase-shifting angle. With this modulation scheme, the current stress and cyclic power loss can be reduced by adjusting the modulation ratio of the inductor current waveform. As a result, the light-load efficiency can be improved compared with the conventional symmetric modulation scheme. The power characteristic, current stress, soft switching characteristic, and backflow power of this modulation strategy are analyzed and calculated comprehensively. Then, based on this asymmetric strategy, a hybrid modulation strategy that can achieve ZVS over the entire power range with low current stress, low return power, and minimum rms current at light load is proposed. Finally, a 100–50 V/300 W prototype is built to verify the analysis.

Investigation on Performance of Various Power Control Strategies with Bifilar Coil for Induction Surface Melting Application

In recent years, induction heating applications assisted by electronic power control have been very appealing. For melting applications, induction heating is widely used as it seems to be appropriate and provides higher efficiency, zero pollutants, non-contamination of material, etc. in comparison with conventional heating. The conventional variable frequency control scheme is not sufficient for melting applications because of its high switching loss, low efficiency, and lower heat rate. A superlative control technique is required to control the output power smoothly, for a high heating rate with minimum power loss, and to lower the number of components. In this paper, a capacitorless self-resonating bifilar coil is proposed for induction surface melting applications. The performance of the system in terms of modular losses, heat rate, and efficiency is analyzed for various power methods such as pulse duty cycle control, phase shift control, pulse density modulation control, and asymmetric duty cycle control. An experimental validation is performed for the 1 kW prototype, and the heating rate, efficiency, and modular losses are calculated. The control technique is digitally validated using a PIC16F877A microcontroller with 30 kHz switching frequency. The temperature distribution is analyzed using a FLIR thermal imager. Among the tested methods, pulse density modulation-based control provides smooth and varied power control from 0% to 100% with minimum modular losses. The efficiency of the system is 89% at a rated output power and is greater than 85% for pulse density modulation control with a fast heating rate.

Independently Controllable Dual-Output Half-Bridge Series Resonant Converter for LED Driver Application

This article presents a dual-output series resonant converter (SRC)-based light-emitting diode (LED) driver, which utilizes three switches to form two half-bridge networks. The proposed three-switch two-half-bridge structure provides reduced switch count and independent control. It uses asymmetric duty cycle control to regulate the LED operating currents and utilizes a low-frequency pulsewidth modulation (PWM) dimming scheme for each half-bridge to control the illumination of each LED load independently. All the switches in the proposed converter operate with zero-voltage turn-on to reduce the switching losses. The operating principle and detailed analysis of the proposed converter is presented and verified with experimental studies for a total load of 50 W (i.e., LED load-1 26 W and LED load-2 24 W). Also, a comprehensive comparative study of the proposed LED driver with recent counterparts is presented.

Photovoltaic Cell Energy Transfer System Using Series-Connected Bidirectional Resonant Converters

This paper presents an energy transfer system for a photovoltaic module with solar-powered panels, batteries, and a grid-tie inverter that uses series-connected bidirectional resonant converters. The purpose of this study is to investigate the asymmetrical duty cycle control and frequency control techniques for increasing and controlling the input voltage of the grid-tie inverter. Prior to the experiment, the performance of the bidirectional resonant converters was evaluated using a simulation program. By adjusting the asymmetrical duty cycle by 50%, the input voltage of the grid inverter was found to be 48.2 V. However, by adjusting the asymmetrical duty cycle by 10%, the input voltage of the grid inverter was 150.4 V. Furthermore, when turning on the switch in the zero-voltage switching (ZVS) mode, the converter circuit was controlled and operated within an appropriate frequency range. The results revealed no switching losses when the converters were turned on. As a result, the bidirectional resonant converters were able to properly transfer energy and regulate the input voltage of the grid inverter.