Resonant DC-DC Converter Research Articles

Design and Control of Series Resonant DC-DC Converter for DC Wind Turbines

High power reliability and high energy density are always in demand, and this is driving the evolution of power conversion technologies. People have begun to examine the potential positions of dc systems in both current and future power equipment due to the rise in the use of renewable energy and the implementation of energy storage in recent decades. Because of its efficiency and power density, dc voltage representation has found use in a wide range of fields, including data centres, the aerospace industry, and dc micro-grids. Resonant DC-DC converters, with their gentle switching and minimal EMI, provide a promising solution to these problems. Finding and examining the various modes of operation of the converter while employing the pulse-removal approach is the primary objective of this study. The new method of operation utilises variable frequency and variable phase displacement in sub-resonant mode, which promises to reduce the transformer size while also facilitating the soft-switching change of the insulated gate bipolar transistors (IGBTs) and line frequency diodes on the rectifier side. The pulse elimination approach, a revolutionary mode of operation for the converter, involves phase and frequency shift modulation at varying rates. Using the results of MATLAB/SIMULINK simulations, the suggested control technique may be utilised to establish the baseline switching function configuration necessary to attain high power efficiency.

Design and Control of Series Resonant DC-DC Converter for DC Wind Turbines

High power reliability and high energy density are always in demand, and this is driving the evolution of power conversion technologies. People have begun to examine the potential positions of dc systems in both current and future power equipment due to the rise in the use of renewable energy and the implementation of energy storage in recent decades. Because of its efficiency and power density, dc voltage representation has found use in a wide range of fields, including data centres, the aerospace industry, and dc micro-grids. Resonant DC-DC converters, with their gentle switching and minimal EMI, provide a promising solution to these problems. Finding and examining the various modes of operation of the converter while employing the pulse-removal approach is the primary objective of this study. The new method of operation utilises variable frequency and variable phase displacement in sub-resonant mode, which promises to reduce the transformer size while also facilitating the soft-switching change of the insulated gate bipolar transistors (IGBTs) and line frequency diodes on the rectifier side. The pulse elimination approach, a revolutionary mode of operation for the converter, involves phase and frequency shift modulation at varying rates. Using the results of MATLAB/SIMULINK simulations, the suggested control technique may be utilised to establish the baseline switching function configuration necessary to attain high power efficiency.

Load-Independent Class E2 Parallel Resonant DC–DC Converter

This brief presents load-independent Class E2 parallel resonant dc-dc converter, which consists of load-independent Class E parallel resonant inverter and load-independent synchronous Class E voltage-driven low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dv/dt$ </tex-math></inline-formula> resonant rectifier. The proposed converter achieves zero-voltage-switching (ZVS) and zero-voltage-derivative-switching (ZVDS) at a rated load resistance, and maintains ZVS and a constant dc output voltage over a wide range of load resistance without additional elements or feedback control. The validity of the operation was confirmed by circuit simulation using LTspice and circuit experiments.

An Expandable High Voltage-Gain Resonant DC-DC Converter With Low Semiconductor Voltage Stress

A high voltage-gain resonant DC-DC converter is proposed in this brief, where a coupled-inductor with multiple windings is adopted. The proposed converter is composed of a boost unit with input-output in series connection and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z(z &gt; 1)$ </tex-math></inline-formula> expandable units. Each expandable unit includes two secondary windings of the coupled-inductor and two leakage-inductor-resonant-capacitor cells. The secondary windings are helpful to get a high voltage-gain, while the resonant cells are helpful to realize zero-current-switching for all diodes. Moreover, all the semiconductors can be thought as in series connection, leading the voltage stresses much lower than the output voltage, especially that of the switches. A laboratory prototype with two expandable units is built to verify the proposed converter.

A Bidirectional DHC-LT Resonant DC-DC Converter with Research on Improved Fundamental Harmonic Analysis Considering Phase Angle of Load Impedance

This paper presents a novel 400 V–50 V bidirectional DHC-LT resonant DC-DC converter. By adding a resonant capacitor and an auxiliary transformer based on LLC, zero-voltage switching (ZVS) and zero-current switching (ZCS) are achieved, while the output voltage gain range is broadened in two directions. Operation principles and robustness are discussed with equations. Then, the error factor of fundamental harmonic analysis (FHA) in resonant converters is analyzed. Considering the phase difference between the output voltage and resonant tank current, an improved method is proposed to describe the behavior of the DHC-LT converter more precisely. A comparison is conducted to prove the effectiveness of the proposed FHA. Furthermore, in order to reduce the output voltage and provide a ripple-free charging current, a fixed-frequency phase-shift strategy is introduced in the DHC-LT converter. ZVS can be realized through the reasonable design of dead time and phase-shift angle. Finally, a 2.5 kW prototype of the DHC-LT resonant DC-DC converter with a digital signal processor (DSP) platform and a battery/PV DC test system is established in the lab to validate the theoretical analysis.

Design of LLC resonant converter with silicon carbide MOSFET switches and nonlinear adaptive sliding controller for brushless DC motor system

Introduction. The high voltage gain DC-DC converters are increasingly used in many power electronics application systems, due to their benefits of increased voltage output, reduced noise contents, uninterrupted power supply, and ensured system reliability. Most of the existing works are highly concentrated on developing the high voltage DC-DC converter and controller topologies for goal improving the steady state response of brushless DC motor driving system and also obtain the regulated voltage with increased power density and reduced harmonics, the LLC resonant DC-DC converter is implemented with the silicon carbide MOSFET switching devices Problem. Yet, it facing the major problems of increased switching loss, conduction loss, error outputs, time consumption, and reduced efficiency. Also the existing works are mainly concentrating on improving the voltage gain, regulation, and operating performance of the power system with reduced loss of factors by using the different types of converters and controlling techniques. The goal of this work is to obtain the improved voltage gain output with reduced loss factors and harmonic distortions. Method. Because, this type of converter has the ability to generate the high gain DC output voltage fed to the brushless DC motor with reduced harmonics and loss factors. Also, the nonlinear adaptive sliding controller is implemented to generate the controlling pulses for triggering the switching components properly. For this operation, the best gain parameters are selected based on the duty cycle, feedback DC voltage and current, and gain of silicon carbide MOSFET. By using this, the controlling signals are generated and given to the converter, which helps to control the brushless DC motor with steady state error. Practical value. The simulation results of the proposed LLC silicon carbide MOSFET incorporated with nonlinear adaptive sliding controller controlling scheme are validated and compared by using various evaluation indicators.

A comparison of P5, Cuk and class E 2 converters for WPT in EV battery charging

This paper presents three DC-DC converter topologies, P5, Cuk and a class E2 converter to compare their performance in the context of wireless power transfer for electric vehicle battery charging. The comparisons use MATLAB simulation to explore the abilities of the system to produce the desired outputs, efficiency, and ability to operate under changing load and coupling factor conditions. The paper highlights current issues with resonant DC-DC converters for wireless electric vehicle battery charging. It also serves to draw parallels between the new application of Cuk and P5 converters for WPT, and that of the Class E2 topology which is better understood within the context of wireless power transfer. The promising feature of Buck-Boost DC-DC converters for wireless power transfer is the ability to control output voltage from the duty cycle. This controllability opens new avenues for creating robust systems under varying coupling factors and loads. The Buck-Boost converter-based systems also benefit from a reduction in overall converters needed and a lower operating frequency than that of Class E2 converters.

TAB Series-Resonant DC-DC Converter and Multi-Phase-Shift Based Global Optimization Modulation

In this paper, a triple-active-bridge resonant dc-dc converter with the ability of topology-level power decoupling is proposed. The power coupling between the two dc ports is eliminated by adding a resonant capacitor to the common port. The operation principle and the steady-state power characteristics are analyzed. On this basis, a multi-phase-shift-based global optimization modulation is proposed to minimize the RMS values of the transformer currents in the entire power and voltage range, thus increasing the global efficiency. An experimental prototype is built to verify the correctness and availability of the proposed power decoupling topology and optimized modulation.

A Comprehensive Review: Topology, Modeling and Control Techniques of Resonant Converter for Electric Vehicle Applications

This paper proposes the comprehensive review on the different resonant converter topologies, different modelling techniques, and different control techniques are being used in electric vehicle application. This paper also discusses the merits and demerits of different modulation/control techniques. The performance of variable frequency control technique can be improvised using SSPM is discussed in this paper. Optimal projectory control method has a quick transient response than SSPSM followed by SSOC, then PSM, and finally by VF controller are reviewed in detail in this study. Cyclic averaging is an accurate alternative method for state variable, this approach is used for time domain analysis of resonant dc-dc converter has been emphasized in this paper. Reverberation would be beneficial when series and parallel resonance converters combined are explained in this paper. LLC topology would be best suitable for electric vehicle applications are discussed and structure of the resonant converters, power efficiency, compatibility and its suitable applications are presented in this paper. A detailed study of modelling techniques to address the increasing demand for electric vehicles are presented.

Fault-Tolerant Operation of a Multimode Stacked Switch Rectifier Leg Through Built-In Circuit Redundancy

In this paper, the open-circuit fault-tolerant operation of a multi-mode stacked switch rectifier leg is presented and investigated. A fault-tolerant control technique is proposed through the built-in circuit redundancy operation of the presented multi-mode stacked switch rectifier leg. A bidirectional CLLC resonant DC-DC converter that employs the presented leg is used to demonstrate the features of the presented control scheme. The proposed control is able to allow post fault operation of the converter to continue to deliver the demanded load power with soft-switching operation in case any switch experiences an open-circuit fault. In addition, the built-in circuit redundancy of the leg allows the resonant converter to operate in different operating modes, resulting in an enhanced control in regulating the output voltage while avoiding the switching frequency to diverge far from the resonant frequency, leading to better performance and improved efficiency with the complete soft-switching operation before and after the fault. To highlight the merits of the proposed fault-tolerant control in the multi-mode stacked switch rectifier leg, experimental results are provided on a 300W resonant converter prototype with an input of 250V and an output voltage of 400V.

Characteristics Analysis and Design of a Resonant dc–dc Converter With ZCS and Short-Circuit Fault Current Limiting Capability

The series resonant dc-dc converter (SRC) which features zero current switching (ZCS) and open-loop control is widely used for providing galvanic isolation and voltage scaling. However, output short-circuit (OSC) fault is a challenge for SRC because it will cause dramatically high current in the low-impedance resonant tank. To address this issue, a resonant full-bridge dc-dc converter only using small dc-side capacitors to resonate with the resonant inductor Lr is proposed. Under normal condition, ZCS can be achieved. When OSC fault occurs, the output dc-side capacitor can be bypassed by the anti-paralleled diodes of the full bridge and the resonant current can be limited automatically by the resonant inductor Lr without additional control. The operation principle of the converter under normal and faulty condition is analyzed. Based on these analyses, the switching frequency to achieve ZCS is designed. The resonant inductor Lr and dc-side resonant capacitors Cr design considerations are provided. The ZCS characteristics and the current limiting capability of the converter are verified on an experimental prototype.

Transient Modulation for the Step-Load-Change Process in a Dual-Bridge Series Resonant Converter

A phase-shifted dual-bridge series resonant DC-DC converter (DBSRC) is a competitive candidate for applications of an energy storage system. At the request of a step-load-change command such as the start-up and power-level change, the converter may suffer from large-amplitude transient oscillations due to improper transient modulation. Furthermore, the DC bias current and overshoot current/voltage in the resonant tank and transformer caused by oscillations may result in transformer saturation and poor dynamic performance. To solve these problems, two fast transient modulation (FTM) methods are proposed in this paper. First, based on the steady-state analysis of the converter with phase-shift control, the current and voltage trajectory of the resonant capacitor can be obtained. Then, the detailed principles of two FTM methods are explained for achieving a smooth transition. Through the adjustment of the durations of the adjacent switching intervals temporarily, the transient trajectory can be predicted and is expected to match the destination trajectory within one switching period. Consequently, the proposed FTM methods enable the converter to move from one steady state to another instantly and the step-load-change transition can be an overshoot-free procedure. Finally, both simulation and experimental tests prove that the two modulation methods can effectively eliminate DC bias current and overshoot current/voltage in the DBSRC transient process and obtain a fast transient response.

Designing of Higher-Order Series-Parallel resonant converter with improved ZVS under variable source condition for constant DC-bus System

Every Renewable based energy source requires an additional buffer unit to deliver power to either a standalone system or a grid system. Most of the time unit buffer either provides constant voltage DC-power or AC-power. Higher efficiency in the conversion process can only be achieved if ongoing losses of the buffer system are low. Square sine control approach for Higher-Order Series-Parallel resonant DC-DC Converter is presented in the paper which provides excellent results in both highly and lightly loaded conditions. This control also provides stable bandwidth for input voltage source acceptance which is mostly to be considered as a PV-based source. The strategy also enhances the reliability of the converter by providing a stable and most delightful way of soft switching triggering so as to maintain the output voltage by un-affecting the switching cycle of the Solid-State Semi-conducting Device (SSSD). Selection for the components used in converter design was also studied with a susceptive case study. Further to this control for the entire converter unit is maintained to single variable control so as to reduce the complexity of the system and enhance efficiency. The simulated results of the programmable single variable square sine-wave control is presented for the higher-order resonant converter operating under variable input condition.

Artificial neural network controller based cleaner battery-less fuel cell vehicle with EF2 resonant DC-DC converter

The evolution of an eco-friendly, sustainable and efficient energy conversion system is becoming inevitable for automotive manufactures and consumers worldwide in the current scenario, especially in highly polluted areas. The use of Fuel Cells (FC) in automotive applications is a lucrative option in response to the critical need for cleaner energy technology. The net voltage output for a single FC is 0.6 to 0.8 V and these cells are arranged in series to form an FC stack. To compensate for FC stack voltage reduction during acceleration of vehicle requires additional battery or ultra-capacitor, which increases the overall cost of the vehicle. An 8 KW FC stack along with Elongation Factor 2 (EF2) resonant converter fed 10 hp Polymer Electrolyte Membrane Fuel Cell (PMSM) drive for powering two-wheelers is proposed which improves the dynamic performance and vehicle reliability. The proposed system reduces the overall size and cost of the FC stack compared to the existing system and regulates the voltage fed to the PMSM drive under different working conditions without additional battery. The proposed drive’s closed-loop speed control is modeled with a State Space Averaged (SSA) dynamic EF2 converter model and a PI controller, followed by a Levenberg–Marquardt algorithm-based Artificial Neural Network (LM-ANN) controller. The performance of the drive is evaluated for various conditions such as starting, climbing, normal running, and braking condition. Comparison of simulation results indicates that EF2 resonant converter operating at greater switching frequency provides high voltage gain at lower duty ratios and LM-ANN based controller seems to be better to provide smooth operation with reduced torque ripple.

RPOL2V5: a compact radiation-hard resonant switched-capacitor DC-DC converter for the CMS HGCAL

A radiation-tolerant resonant switched-capacitor DC-DC converter (rPOL2V5) has been developed to supply the front-end analog and digital circuits for the detectors used in the LHC High Luminosity upgrades. It has been of particular interest to the CMS High-Granularity Calorimeter (HGCAL) community due to its lower volume compared to existing radiation-hard buck converters. rPOL2V5 is based on an ASIC developed using 130 nm CMOS technology. It is powered by a 2.5 V input and it can supply a maximum current from 2 A to 5 A, depending on the output voltage value, which can range from 1 V to 1.5 V. This work presents the strategies adopted at the ASIC and PCB level to bring the converter to maturity, and its electrical and radiation characterisation results.

A Detailed Full-Order Discrete-Time Modeling and Stability Prediction of the Single-Phase Dual Active Bridge DC-DC Converter

The standard methodology to obtain the model of a power electronic converter is achieved by averaging the state-space dynamics of the converter’s state variables. But the average of the transformer current is null over a switching cycle in the resonant dc-dc converter. Therefore, the conventional method is not suitable for resonant converters, including the phase-shifted bidirectional dual active bridge (PSBDAB) converter. The two-time scale discrete-type models can resolve the problem associated with the standard state-space averaging methodology. The time-scale segregates the dynamics of the PSBDAB converter into fast and slow state variables, which can be modeled separately and eases the analysis of the PSBDAB converter. The effect of the core-loss of the inductor, dead-time of the semiconductor devices, output filter capacitor’s equivalent series resistance, semiconductor on-resistance, and the transformer copper loss components are included in the model to improve its steady-state and dynamics characteristics. Moreover, the stability analysis using a bifurcation diagram is carried out for the digitally controlled closed-loop of the system. Furthermore, the critical gain for the stable region with variations in the circuit parameters like load resistance, circuit equivalent inductance, and voltage demand is extensively studied. The modeling and stability analysis is validated in the simulation and experimental setup. The results verify that the proposed method accurately predicts the stable region with variations in the system circuit parameters. Thus this study provides a guide to select and tune the controller parameter to ensure the converter operates within the boundaries of the stable region.

Analysis and Design of High-Efficiency Modular Multilevel Resonant DC-DC Converter

This paper demonstrates a high-efficiency modular multilevel resonant DC-DC converter (MMRC) with zero-voltage switching (ZVS) capability. In order to minimize the conduction loss in the converter, optimizing the root-mean-square (RMS) current flowing through switching devices is considered an effective approach. The analysis of circuit configuration and operating principle show that the RMS value of the current flowing through switching devices is closely related to the factors such as the resonant tank parameters, switching frequency, converter output voltage and current, etc. A quantitative analysis that considers all these factors has been performed to evaluate the RMS current of all the components in the circuit. When the circuit parameters are carefully designed, the switch current waveform can be close to the square waveform, which has a low RMS value and results in low conduction loss. And a design example based on the theoretical analysis is presented to show the design procedures of the presented converter. A 600 W 48 V-to-12 V prototype is built with the parameters obtained from the design example section. Simulation and experiments have been performed to verify the high-efficiency feature of the designed converter. The measured converter peak efficiency reaches 99.55% when it operates at 200 kHz. And its power density can be as high as 795 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

High voltage gain resonant DC-DC converter with vm cells for renewable sources applications

Due to the widespread impact of renewable energy resources on high power density grids, transmission at the DC regime has been considered more useful than AC transmission systems. The findings of this study suggest the application of a ripple-free input current resonant DC-DC converter possessing high voltage gain and high efficiency as being more suitable for renewable energy systems. Applying variable switching frequency control systems, the proposed converter discussed here is generally operated at the critical conduction mode for soft switching of the semiconductor switches. Using the resonance mechanism, the proposed converter causes a decrease in the turn-on loss of the power switch without needing additional semiconductor gadgets. It leads to a reduction in the reverse-recovery losses of the rectifying diodes. Also, analysis and design consideration of the proposed converter are presented with excellent performance.

Non‐resonant soft‐switching technique with linear current on switching cycle time‐scale for switched‐capacitor DC‐DC converters

The switched-capacitor DC-DC converters have been widely applied to convert energy from low voltage to DC bus for the power generation systems with fuel cells, photovoltaic array, and so on. However, the large capacitance is generally selected to eliminate the high current spike of switched-capacitors in the hard-switching switched-capacitor (SC) DC-DC converters, which will lead to the large volume and weight of capacitors and of converters. To solve this problem, a non-resonant soft-switching (NRSS) technique with linear current on switching cycle time-scale for switched-capacitor DC-DC converters is first proposed in this paper, which achieves zero-current-switching (ZCS) turn-on of switches and ZCS turn-off of diodes with linear current on switching cycle time-scale. In detail, the NRSS technique is proposed based on the idea that the current of an auxiliary inductor on switching cycle time-scale is considered as the linear parts for the resonant current of the auxiliary inductor on resonant cycle time-scale. The proposed NRSS technique is utilized into SC DC-DC converter and the current spikes of switches can be reduced to two third by using the same capacitance compared with the hard-switching SC DC-DC converters and be reduced to a third compared with the resonant soft-switching SC DC-DC converters. Further, nine new soft-switching SC DC-DC converters, with single switch and double switches, are built based on the proposed non-resonant soft-switching technique. Finally, the non-resonant soft-switching technique is verified theoretically and experimentally by three of the nine proposed SC DC-DC converters. This paper provides a new way to realize soft-switching during the non-resonant interval on switching cycle time-scale and a new method to significantly reduce the required capacitance in SC DC-DC converters.

A Review on State-of-the-Art Power Converters: Bidirectional, Resonant, Multilevel Converters and Their Derivatives

With the rapid development of modern energy applications such as renewable energy, PV systems, electric vehicles, and smart grids, DC-DC converters have become the key component to meet strict industrial demands. More advanced converters are effective in minimizing switching losses and providing an efficient energy conversion; nonetheless, the main challenge is to provide a single converter that has all the required features to deliver efficient energy for different types of modern energy systems and energy storage system integrations. This paper reviews multilevel, bidirectional, and resonant converters with respect to their constructions, classifications, merits, demerits, combined topologies, applications, and challenges; practical recommendations were also made to deliver clear ideas of the recent challenges and limited capabilities of these three converters to guide society on improving and providing a new, efficient, and economic converter that meets the strict demands of modern energy system integrations. The needs of other industrial applications, as well as the number of used elements for size and weight reduction, were also considered to achieve a power circuit that can effectively address the identified limitations. In brief, integrated bidirectional resonant DC-DC converters and multilevel inverters are expected to be well suited and highly demanded in various applications in the near future. Due to their highlighted merits, more studies are necessary for achieving a perfect level of reducing losses and components.