Multi-resonant Converter Research Articles

Dual LC parallel multi‐resonant DC‐DC converter with wide output‐voltage range

SummaryAlthough LLC converters have widespread applications due to their advantages of high efficiency, high power density, and soft switching, in wide voltage gain range applications, a large switching frequency range is inevitably required, which may bring difficulties in converter design and efficiency improvement. In this paper, a dual LC parallel multi‐resonant converter (MRC) is introduced. The converter contains two parallel LC resonant branches in the resonant tank, which exhibit the notch filter characteristic on the gain curve. It enables the converter to provide wide voltage gain regulation, soft startup, and overcurrent protection over a limited frequency range. Compared to other five‐element MRCs, since the converter provides different current loops for the fundamental wave and the third harmonic to transmit active power, the circulating reactive energy and stress on the resonant components are reduced. Finally, a detailed design procedure for a 3.3 kW converter prototype with an output voltage range of 250–450 V is provided.

Geometrical State-Plane Analysis of Resonant Switched-Capacitor Converters: Demonstration on the Cascaded Multiresonant Converter

To realize high efficiency and high power density for resonant switched capacitor (ReSC) converters, it is critical to have a thorough understanding of the soft-switching mechanism and design the converter appropriately. However, this can be challenging as the soft-switching operation depends on multiple variables and its design difficulty increases quickly with respect to the topology complexity. This paper demonstrates a framework of using geometrical state-plane analysis to facilitate ReSC converter design. The methodology is first applied to a basic 2-to-1 ReSC converter, and then extended to a new 4-to-1 ReSC converter topology we proposed, herein named cascaded multi-resonant converter. This topology has reduced component count thanks to a new “switching bus” architecture. However, it comes at a cost as the converter has multiple resonances within each switching cycle, complicating the soft-switching design. Despite the high circuit complexity, the state-plane analysis neatly provides analytical equations of all state parameters, which are verified by simulations and experiments. Our hardware prototype achieves 6000 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density at 48-to-12 V conversion and 80 A continuous output. Its peak efficiency reaches 99.02%, and full-load efficiency reaches 97.67%, including gate drive loss. Both the power density and efficiency are superior to the state-of-the-art 48-to-12 V solutions.

Modeling of Buck ZVS Multiresonant DC-DC Converter Using Bond Graphs

Pulse width modulated (PWM) converters are suffering from poor efficiency due to high switching losses. quasiresonant converters with the help of resonance phenomenon can come to the rescue of PWM converters. There are certain problems even with the quasiresonant converters. Problems with quasiresonant converters such as parasitic oscillations and high voltage stress can be resolved with the help of multiresonant converters. Appropriate modeling technique is needed to accurately represent the physical system. The multiresonant converters along with electrical systems are involved in magnetic and thermal systems. For this kind of systems, the appropriate modeling is bond graph. In this piece of work, buck ZVS multiresonant converter is taken to model using bond graphs. The large signal bond graph model is created. In MATLAB/SIMULINK for state variables the created bond graph model is simulated. The findings obtained are checked with PSIM simulated results and experimental results. The comparison of model and experimental results prove the model’s accuracy.

Analyzing the Effect of Parasitic Capacitance in a Full-Bridge Class-D Current Source Rectifier on a High Step-Up Push–Pull Multiresonant Converter

This paper presents an analysis on the effect of a parasitic capacitance full-bridge class-D current source rectifier (FB-CDCSR) on a high step-up push–pull multiresonant converter (HSPPMRC). The proposed converter can provide high voltage for a 12 VDC battery using an isolated transformer and an FB-CDCSR. The main switches of the push–pull and diode full-bridge rectifier can be operated under a zero-current switching condition (ZCS). The advantages of this technique are that it uses a leakage inductance to achieve the ZCS for the power switch, and the leakage inductance and parasitic junction capacitance are used to design the secondary side of the resonant circuit. A prototype HSPPMRC was built and operated at 200 kHz fixed switching frequency, 340 VDC output voltage, and 250 W output power. In addition, the efficiency is equal to 96% at maximum load. Analysis of the effect of the parasitic junction capacitance on the full-bridge rectifier indicates that it has a significant impact on the operating point of the resonant tank and voltage. The proposed circuit design was verified via experimental results, which were found to be in agreement with the theoretical analysis.

Evaluation of DCX converters for off-grid photovoltaic-based green hydrogen production

Photovoltaic (PV) to electrolyzer power systems are an attractive research topic since the PV produced power can be optimized by skipping power conversion into AC and producing a direct DC-DC interface. Existing DC-DC power conversion systems to directly interface the PV generation and Hydrogen (H2) electrolyzer are mainly based in interleaved structures or multi-resonant converters. Soft-switching characteristics are also suitable for these conversion topologies and DCX converters are then serious candidates to be used. DCX provides an isolated high efficiency solution but the DCX-based two-stage converter topology must be optimized in order to obtain better efficiency and energy yield. In this work a detailed comparison of DCX topologies is given for a PV to H2 application. The proposed optimized system is validated through simulation in a multi-string electrolysis system, showing the relevance of the solution for this application. The proposed approach reaches a global maximum efficiency of 98.2%.

A Novel Multiresonant DC–DC Converter With Wide Output-Voltage Range

A novel multiresonant dc–dc converter with notch filter function is proposed in this article. The converter can regulate the output voltage over a wide range and has significant advantages in terms of gain. Due to its gain characteristics, the multiresonant converter has better inherent soft startup capability and over-current protection function. In addition, the switches of the converter can realize zero-voltage switching over the entire output-voltage range, and the output rectifier diode can realize zero-current switching. Compared with the traditional LLC converter, the multiresonant converter can use third harmonic to transmit the active power, and the loss caused by the reactive power cycle of the converter is reduced, which improve the efficiency. The converter parameters are optimized from the perspective of gain and efficiency in this article. Finally, a 2.5-kW experimental prototype is designed and the peak efficiency is 97.27%. The correctness of the theoretical analysis and the rationality of the parameter design are proved by the experimental results.

Design considerations of the multi-resonant converter as a constant current source for electrolyser utilisation

An electrolyser is a current driven device, and the volume of produced hydrogen is proportional to the applied current density. To achieve optimal and efficient hydrogen production, it is necessary to calculate current to feed electrolyser and keep it constant despite the input voltage change, number of stacks, temperature, pressure or resistance change of each stack. A systematic design procedure of high frequency DC-DC multi -resonant converter as a constant current source optimized for interfacing electrolyser stack to DC voltage source is presented. The multi resonant converter can operate in four different modes of operation. Each mode of operation represents a specific four-stage sequence characterized by resonating specific part of multi element resonant network. The advantage of this type of converter is that all major parasitic reactances are included in resonant processes. The converter performs Zero Voltage Switching and Zero Current Switching on all switching components depending on the operation mode. The favourable switching conditions are not achievable throughout the whole operating range. The optimal switching region in DC conversion ratio characteristics is calculated and emphasized. The design presented in this paper is based on the mapping of the desired converter operating area in DC conversion ratio characteristic and the calculation of component values using parameters that derive from the selected operating area. The realized converter prototype operates in Mode I with high full load efficiency. The high partial load efficiency is maintained down to 50% of the full load. The realized converter maintains a constant output current with low switching frequency change. The zero voltage switching is achieved both for the power switches and rectifier diodes throughout the load range.

A Novel D-CLT Multi-Resonant DC-DC Converter with Reduced Voltage Stresses for Wide Frequency Variation Applications

In this paper, a dual-capacitor-inductor-transformer (CLT) (D-CLT) soft-switching dc–dc converter has been proposed. Combining the multiresonant technology, the converter employs two high-frequency transformers in the resonant tank and exhibits desirable characteristics. The fundamental and the third-order harmonics can be utilized to transfer active power simultaneously. The share of third harmonic is larger than first component. Thus, the converter can use the 100-kHz controlling signals to mainly transfer the 300-kHz active power, which makes it easier to realize high power density. Moreover, the available range for the third power delivery is expanded as well. A resonant zero point is introduced into the voltage gain curves. It ensures broadened voltage gain range (from zero to the maximum) and good protection for overcurrent issue. Then, improved soft-switching performances have been achieved: All the switches achieve the zero-voltage-switching (ZVS) turn- on , whereas all the diodes obtain the zero-current-switching (ZCS) turn- on and quasi-ZCS turn- off . Switching losses are constrained to the minimum. To verify the feasibility of the proposed converter, a 330-W prototype is established and tested. The results demonstrate the experiments match well with the theoretical analyses. The peak efficiency has reached 95.2%, although a high-loss diode bridge is adopted.

MHz zero‐voltage‐switched isolated resonant converter for wide‐output‐voltage application

This study proposes a MHz isolated resonant converter, which achieves buck–boost DC/DC conversion, zero-voltage switching and the resonant components absorb the parasitic parameters. The DC analysis method and MATLAB computational algorithm are proposed for acquiring the specific circuit characteristics, including the voltage conversion ratio, the rms value of switch current and peak voltage of the semiconductors. The active power and apparent power are also analysed to provide design basis of optimising efficiency. The proposed converter shows greater advantages on voltage stress, current stress and efficiency over traditional isolated Sepic multi-resonant converter. A wide-output-voltage prototype based on the proposed converter was built in the lab and the experimental results verify the theoretical analysis well.

Comparative Analysis and Optimization of Power Loss Based on the Isolated Series/Multi Resonant Three-Port Bidirectional DC-DC Converter

Based on the loss distribution and efficiency analysis, a comparative study between a series resonant three-port bidirectional DC-DC converter (SR-TBC) and a multi-resonant three-port bi-directional DC-DC converter (MR-TBC) is reported here. By using the Fourier equivalent analysis method in hand, the resonant current, switching current expressions, zero voltage soft switching (ZVS) conditions of MR-TBC and SR-TBC are deduced. Besides, in consideration of efficiency and soft switching aspects, the loss models of main power components and resonant elements are integrated and optimized for both topologies. Their loss distributions are established, and the different effects derived from the adoption of SiC MOSFET and Si MOSFET on the converter efficiency are discussed. Finally, to verify the theoretical analyses, comparative experiments under diverse load states are conducted based on the prototypes of the MR-TBC and SR-TBC. The obtained results demonstrate that the MR-TBC successfully broadens the ZVS range and thus achieves higher efficiency along the entire load range.

Performance Analysis of Photovoltaic Induction Motor Drive for Agriculture Purpose

&lt;p&gt;This paper presents water pumping system using renewable source (solar) without the use of chemical storage batteries. In this converter-inverter circuit is used to drive Induction motor. The Converter used here is Two Inductor boost converter (TIBC), which consists of a resonant tank, voltage doubler rectifier and a snubber circuit. TIBC is designed to drive the three phase induction motor from PV energy. TIBC converter is also known as current fed multi resonant converter having high voltage gain and low input current ripple. Converter switches are controlled through hysteresis controller and ZCS resonant topologies. Solar PV power fluctuates according to irradiation level of sunlight and hence tracking of maximum power at all time is mandatory. SPWM control with third harmonic injection is used to trigger the IGBT’s in the inverter. The development is oriented to achieve a more efficient, reliable, maintenance free and cheaper solution than the standard ones, that uses DC motors or low voltage synchronous motors. The proposed method is verified with MATLAB/SIMULINK and the system simulation confirms the performance of the proposed system.&lt;/p&gt;

A New Application of the Multi-Resonant Zero-Current Switching Buck Converter: Analysis and Simulation in a PMSG Based WECS

A new application of the three-phase buck-resonant converter is presented in this paper. It is shown that the analyzed converter is suitable to operate as the rectifier stage in low power wind energy conversion systems (WECS) based on permanent magnet synchronous generators (PMSG) with variable wind speed. As main features, it presents a single controlled switch, simple implementation and control, and operates with a high power factor and low harmonic distortion over all wind speed ranges. The converter topology, its design equations and its operation are presented, as well as the simulation results of the PMSG based conversion system. From the analysis carried out in the paper it is concluded that the converter is indicated to be employed in distributed generation and hybrid systems where wind generation is associated with other sources.

DC-DC SEPIC CONVERTER TOPOLOGIES

This paper presents different kind of SEPIC converter Topologies. Those are conventional SEPIC converter, multi resonant SEPIC converter and new resonant SEPIC converter. It is a type of dc-dc converters. It can deliver the output voltage that is less than or larger than the input voltage. It is a fourth order dc-dc converter. Basic operating principle of SEPIC converter is ZVS. MOSFET is used as the switch because of low voltage drop. Conventional SEPIC has two bulk inductors. Multi resonant SEPIC converter needs a resonant capacitor and resonant inductor. The bulk inductor reduces the response speed. The new resonant SEPIC converter has small size, excellent transient performance and higher efficiency. Efficient power conversion can be achieved by switched mode RF inverters like class E inverter. The new resonant SEPIC converter is a dc-dc converter with high frequency and efficiency. New resonant SEPIC converter operating at fixed frequency and duty ratio. It reduces the component count and eliminates the need of bulk inductor. The new resonant SEPIC converter is operating at switching frequency of 20 KHz and converter is simulated by using MAT LAB/SIMULINK for 3.6V input supply.

English

The project proposes a new converter for photovoltaic system which is substantially high performance oriented. Furthermore, the lack of batteries replacement water pumping systems without the use of chemicals are responsible for the failure of such systems in isolated areas. The converter is designed to drive a three-phase induction motor directly from photovoltaic system. The majority of commercial systems use low-voltage (PV) energy. The use of three-phase induction motor presents a suitable replacement of dc motor though by the use of dc motor we can directly drive by means of converter dc supply, but due to its lack of performance and reliability, we have opted for three phase induction motor. In the developed technique, there is no specialized personnel for operating and the system is based on a current-fed multi-resonant converter also maintaining these motors. Here, we make use of the TIBC topology such that they are found to be made of Buck Boost converter which will both stabilize and boost the output supply. Thus, the project will be a low cost high efficiency water supply duo for agricultural industry. Though solar energy based water supply system is being developed for the past 20 years, this project will be a phenomenal change and development of renewable energy that could be used in agricultural industry projects.

Design and Analysis of a Full-Bridge LLC-Based PEV Charger Optimized for Wide Battery Voltage Range

In this paper, a two-stage onboard battery charger is analyzed for plug-in electric vehicles (PEVs). An interleaved boost topology is employed in the first stage for power factor correction (PFC) and to reduce total harmonic distortion (THD). In the second stage, a full-bridge LLC-based multiresonant converter is adopted for galvanic isolation and dc/dc conversion. Design considerations are discussed, focusing on reducing the charger volume and optimizing the conversion efficiency over the wide battery-pack voltage range. A detailed design procedure is provided for a 1-kW prototype, charging the battery with an output voltage range of 320-420 V from 110-V 60-Hz single-phase grid. Experimental results show that the first-stage PFC converter achieves THD of less than 4% and a power factor higher than 0.99, and the second-stage LLC converter operates with 95.4% peak efficiency and good overall efficiency over wide output voltage ranges.

Implementation of a High-Efficiency, High-Lifetime, and Low-Cost Converter for an Autonomous Photovoltaic Water Pumping System

This paper proposes a new converter for photovoltaic (PV) water pumping or treatment systems without the use of chemical storage elements, such as batteries. The converter is designed to drive a three-phase induction motor directly from PV energy. The use of a three-phase induction motor presents a better solution to the commercial dc motor water pumping system. The development is oriented to achieve a more efficient, reliable, maintenance-free, and cheaper solution than the standard ones that use dc motors or low-voltage synchronous motors. The developed system is based on a current-fed multiresonant converter also known as resonant two-inductor boost converter (TIBC) and a full-bridge three-phase voltage source inverter (VSI). The classic topology of the TIBC has features like high voltage gain and low input current ripple. In this paper, it is further improved with the use of a nonisolated recovery snubber along with a hysteresis controller and the use of a constant duty cycle control to improve its efficiency. Experimental results show a peak efficiency of 91% at a rated power of 210 W for the dc/dc converter plus the three-phase VSI and a peak efficiency of 93.64% just for the dc/dc converter. The system is expected to have a high lifetime due to the inexistence of electrolytic capacitors, and the total cost of the converter is below 0.43 U$/Wp. As a result, the system is a promising solution to be used in isolated locations and to deliver water to poor communities.

An LLC Resonant DC–DC Converter for Wide Output Voltage Range Battery Charging Applications

In this paper, resonant tank design procedure and practical design considerations are presented for a high performance LLC multiresonant dc-dc converter in a two-stage smart battery charger for neighborhood electric vehicle applications. The multiresonant converter has been analyzed and its performance characteristics are presented. It eliminates both low- and high-frequency current ripple on the battery, thus maximizing battery life without penalizing the volume of the charger. Simulation and experimental results are presented for a prototype unit converting 390 V from the input dc link to an output voltage range of 48-72 V dc at 650 W. The prototype achieves a peak efficiency of 96%.

Analysis and Design of a High Step-up Current-Fed Multiresonant DC–DC Converter With Low Circulating Energy and Zero-Current Switching for All Active Switches

A high-efficiency high step-up current-fed multiresonant converter (CFMRC) is proposed for interfacing the sustainable power sources, such as PV panels and fuel cells, which are characterized by low-voltage high-current output and have strict current ripple requirement. The proposed converter has the features of low input current ripple, low circulating energy, achieving zero-current switching (ZCS) for all active switches, and common ground driving. In order to further improve the efficiency and the power density of the CFMRC, coupled inductor and voltage doubler are applied to the two input inductors and the output rectifier, respectively. The operation principle of the CFMRC is introduced. Its dc voltage gain and the ZCS conditions of both the primary switches and the secondary rectifier are also derived based on the steady-state analysis. Finally, a design guideline is given. The theoretical analysis of the CFMRC was verified on a 150-W prototype. An average efficiency of 95.9% was achieved over the entire maximum power point tracking range (23-38 V), with a 350-V output at full load.

A Current-Fed Multiresonant Converter with Low Circulating Energy and Zero-Current Switching for High Step-Up Power Conversion

A high-efficiency high step-up dc-dc converter is proposed for renewable energy harvesting, where the sustainable power sources, such as PV panels and fuel cells, are characterized by low-voltage high-current output. The proposed converter employs the current-fed half-bridge structure to generate a square-wave current source. Then, a multiresonant tank is used to provide high voltage gain, absorb the parasitic parameters of the transformer, and create zero-current switching (ZCS) condition for all primary switches. By applying a single capacitor instead of LC for the output filter, the maximum voltage of the resonant capacitor is clamped to the output voltage, which reduces the circulating energy within the circuit and offers ZCS to the rectifying diodes. The operation principle is introduced and the steady-state analysis is also carried out for the derivation of the dc voltage gain and the ZCS conditions of the primary switches. The performance of the proposed converter was verified by a 150-W prototype. A peak efficiency of 95.2% was achieved by running the prototype at 255 kHz with 23-V input and 350-V output.

The Multiresonant Converter Steady-State Analysis Based on Dominant Resonant Process

The steady-state analysis of the multiresonant converter is presented. The multiresonant converter utilizes multielement resonant network that consists of resonant inductor and switch capacitances. The resonant process between resonant inductor and capacitances across rectifiers has been found as dominant resonant process. All key circuit parameters are normalized in terms of the characteristic impedance and resonant frequency given by resonant inductor and capacitances across rectifiers. The effects of the transformer magnetizing and leakage inductances have been analyzed. It is shown that dc output values and resonant current rms value strongly depend on load and switching frequency to resonant frequency ratio. It is shown that the resonant process of the resonant inductor and MOSFET output capacitances have no significant influence on overall dc conversion ratio at heavy loads. The simplified analysis is presented and resonant tank order is reduced. The circuit utilizes four different modes of operation. In each mode of operation, the 2-D state-plane diagram is derived. The dc conversion ratio, normalized rms MOSFET, and rectifier capacitance currents have been calculated. A 2.5-kW prototype has been built and tested.