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ABSTRACT Based on the fractional‐order (FO) characteristics of inductors and capacitors, many basic PWM DC–DC converters are defined and modeled by FO calculus in previous studies, but the research of FO resonant dc converters is still in its early stage. Therefore, this paper adopts FO calculus and Laplace transform to model and analyze a ZCS boost converter with an LC resonant tank, which mainly focuses on the influence of the FO component on the soft switching characteristics, converter efficiency, and output voltage gain of this isolated dc converter. This paper extends the topology to the fractional order domain and conducts FO modeling. The order of the resonant inductor and capacitor will affect the amplitude/phase of the resonant current and then affect the converter ZCS characteristic. The analysis demonstrates that the reduction of FOI and FOC order is not conducive to the ZCS of switching devices and converter efficiency. Based on the voltage and current relationship of the FO LC resonant tank, a parameter design guideline is presented. Numerical tools are used to solve the FO output voltage gain and draw the gain curve. And the order of FOI and FOC provides new flexibility for the converter output gain and soft switching design. Finally, simulations and a 360 W hardware experimental prototype are conducted to verify the accuracy and effectiveness of theoretical analysis. [ABSTRACT FROM AUTHOR]

ABSTRACT To address the issue of significant loss increase in planar transformers at high frequencies in LLC resonant converters, the winding width of the transformer was optimized. This design minimizes losses due to eddy currents and skin effects, thereby optimizing the transmission efficiency of the LLC resonant converter. This paper developed a mathematical model of the transformer windings, analyzed the losses in the windings and the core of the planar transformer, and summarized the design rules for three commonly used winding geometries. By determining the optimal winding width, the transformer losses were optimized. Using the finite element simulation software Maxwell3D, a 3D simulation model of the transformer was constructed. The simulation results were compared, and a 500‐W full‐bridge LLC prototype was built to validate the principles summarized in the paper. [ABSTRACT FROM AUTHOR]

In recent years, wide voltage range DC/DC converters have been widely used in telecom power, solar generation and electric vehicle charger applications. Based on this, a new multi‐resonant converter with wide input voltage is proposed here. Compared with the traditional LLC converter, the proposed converter can maintain the output voltage within a narrow frequency regulation range in both under‐resonance and over‐resonance areas. Thus, a wide voltage range can be realized without additional switch components or complex control strategies. The topology and the corresponding working principle of the proposed converter are introduced. In addition, the equivalent model by considering the fundamental wave is established and the influence of the resonance parameters on the voltage gain characteristic is analysed in detail. With these considerations, the resonance parameters are designed. Finally, a 500 W experiment platform is established to verify the effectiveness and feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

Aiming at the problem caused by the fact that traditional on-board charging systems (OBC) usually use a single form of AC input, this research suggests a suitable isolated OBC for single-phase and three-phase power sources. It adopts a two-stage structure. The front stage can switch between different input modes. Using a single-phase AC input mode, the front stage is a totem pole bridgeless cascade Boost circuit for power factor correction (PFC). It can be switched to a three-phase six-switch PFC circuit in a three-phase AC input mode. A full-bridge LLC resonant converter serves as the rear stage. The system adopts a double closed-loop control strategy and a mixed control mode that consists of pulse width modulation (PWM) and pulse frequency modulation (PFM). In either the single-phase or three-phase AC input mode, the front stage PFC circuit can output a 700 V DC bus voltage, and keep the input current and input voltage in phase. It is possible to achieve soft switching in the rear stage resonant converter, and to output a wide range of voltage to charge the power battery. According to a theoretical analysis, a system simulation model is built and an experimental prototype of the OBC is produced. The accuracies of the simulation and the theoretical analysis are confirmed by experimental findings. [ABSTRACT FROM AUTHOR]

This paper discusses the design and analysis of a three-level LLC (TL-LLC) resonant converter for an electric vehicle (EV) charging application. The proposed two-stage onboard charger comprises an ac-to-dc power factor correction (PFC) stage, followed by the second stage required to provide galvanic isolation and dc-to-dc conversion. The PFC stage uses a bridgeless SEPIC converter with average current control and voltage mode control algorithm for achieving unity power factor (pf) operation with constant DC link voltage. In contrast, the dc/dc stage uses a three-level LLC resonant converter with a frequency control algorithm to control the output voltage. A 1 kW, 360 V output model of the proposed onboard charger is implemented and simulated in PSIM, and the obtained results are investigated and examined in detail. Results obtained from the simulation show a power factor greater than 0.99 with THD less than 5 $$\% $$ % at the input side. For TL-LLC, both zero voltage switching (ZVS) for primary MOSFETs and zero current switching (ZCS) for secondary side rectifier diodes are achieved. [ABSTRACT FROM AUTHOR]

Abstract In recent years, wide voltage range DC/DC converters have been widely used in telecom power, solar generation and electric vehicle charger applications. Based on this, a new multi‐resonant converter with wide input voltage is proposed here. Compared with the traditional LLC converter, the proposed converter can maintain the output voltage within a narrow frequency regulation range in both under‐resonance and over‐resonance areas. Thus, a wide voltage range can be realized without additional switch components or complex control strategies. The topology and the corresponding working principle of the proposed converter are introduced. In addition, the equivalent model by considering the fundamental wave is established and the influence of the resonance parameters on the voltage gain characteristic is analysed in detail. With these considerations, the resonance parameters are designed. Finally, a 500 W experiment platform is established to verify the effectiveness and feasibility of the proposed converter.

Abstract Soft switching reduces voltage and current stress during transitions, smoothing and quieting operations and reducing electromagnetic interference while also increasing efficiency and equipment lifespan. Circuit design, component selection, and switching frequency optimization affect power electronics soft switching. This paper proposes boost integrated half-bridge dual-output series resonant (BIHBDOSR) converter, a novel converter design and control method to increase series resonant converter performance by reducing storage element size, switch count, and switching losses. This methodology relies on soft-switching technologies like zero-voltage switching (ZVS) and zero-current switching (ZCS). These methods use class-D, class-E, series, parallel, and series–parallel resonant converter circuits to increase efficiency and minimize component stress. The proposed converter is ideal for constant voltage, constant power, and current-controlled loads with the output voltage being regulated by a closed-loop PI controller. The output voltages for two loads in the simulation depart from reference values. V01 changes from 14 to 20 V and V02 from 18 to 15 V at 300 ms owing to switching variances. The proposed converter utilizes gate driver circuits, resonant tank circuit, current sensor, FPGA board for closed-loop control, and current sensor for stability, ensuring converter stability. The proposed converter closed-loop control method modifies PWM signals to regulate both loads independently and ensure steady output voltage. Additionally, to validate the effectiveness of proposed converter, a 50-W driver circuit is designed, delivering two independent outputs of 20 W and 30 W. Frequency modulation (FM) and duty cycle control methods are employed to obtain the desired outputs.

In this paper, a three-phase single-stage AC-DC converter for an IPT-based small wind power generation system (WPGS) with an S-S compensation circuit is proposed. It applies a three-phase single-stage AC-DC converter to improve the input power factor (PF), efficiency, and reliability in small WPGSs. Also, inductive power transfer (IPT) was applied to compensate for brush wear in the nacelle of small and medium-sized wind turbines while ensuring electrical safety. In conditions of the three-phase Permanent Magnet Synchronous Generator (PMSG) voltage (80~260 Vrms) for the wind turbine and the load (150~1000 W), it was verified that the desired output voltage below 3% can be controlled through the fixed link voltage (VLink) control without wireless communication. A 1 kW prototype was built and tested to demonstrate its applicability to the rotation of small and medium-sized wind turbine nacelles instead of brushes and slip rings. [ABSTRACT FROM AUTHOR]

Soft switching reduces voltage and current stress during transitions, smoothing and quieting operations and reducing electromagnetic interference while also increasing efficiency and equipment lifespan. Circuit design, component selection, and switching frequency optimization affect power electronics soft switching. This paper proposes boost integrated half-bridge dual-output series resonant (BIHBDOSR) converter, a novel converter design and control method to increase series resonant converter performance by reducing storage element size, switch count, and switching losses. This methodology relies on soft-switching technologies like zero-voltage switching (ZVS) and zero-current switching (ZCS). These methods use class-D, class-E, series, parallel, and series–parallel resonant converter circuits to increase efficiency and minimize component stress. The proposed converter is ideal for constant voltage, constant power, and current-controlled loads with the output voltage being regulated by a closed-loop PI controller. The output voltages for two loads in the simulation depart from reference values. V01 changes from 14 to 20 V and V02 from 18 to 15 V at 300 ms owing to switching variances. The proposed converter utilizes gate driver circuits, resonant tank circuit, current sensor, FPGA board for closed-loop control, and current sensor for stability, ensuring converter stability. The proposed converter closed-loop control method modifies PWM signals to regulate both loads independently and ensure steady output voltage. Additionally, to validate the effectiveness of proposed converter, a 50-W driver circuit is designed, delivering two independent outputs of 20 W and 30 W. Frequency modulation (FM) and duty cycle control methods are employed to obtain the desired outputs. [ABSTRACT FROM AUTHOR]

The work presents the calculations of the control characteristics of the full-bridge resonant converter with a series resonant LLC circuit and frequency control by two methods - the first harmonic method and the superposition method. The theoretical results were verified by the analytical-structural modeling method. The power circuit of the resonant converter for the analysis of electromagnetic processes is replaced by a linear T-shaped circuit with two series resonant RLC-circuits and equivalent generators of rectangular voltages, which simulate a transistor inverter and a diode rectifier in the quasi-continuous current mode. Analytical-structural modeling method consists in partly analytical and partly structural ways of building a numerical model of the resonant converter in the form of the simulation model in the MATLAB-Simulink environment. Linear structural links of the model are created on the basis of integral equations of circles. Non-linear links are created based on the non-linear functions and causal relationships. The structural model based on these links takes into account the nonlinearity of the elements of the power circuit of the resonant converter and is based on simpler mathematical expressions compared to the equivalent mathematical model of the resonant converter. The structural model corresponds to the idea of the resonant converter in the form of the resonant circuit with independent equivalent voltage generators and allows to adjust the magnetic coupling coefficient between the transformer windings and simulate processes with arbitrary control functions of equivalent generators. The peculiarity of the use of the superposition method for calculating the static characteristics of the resonant converter is the need to match the voltage phases of the equivalent generators of the equivalent circuit during the changes of the operating frequency or relative load voltage. The dependence of the input voltage of the rectifier, which is simulated by the second equivalent generator, on the processes of the power circuit of the real resonant converter, determines the conditions for matching (adjusting) the phases of the equivalent generators. References 30, figures 5. [ABSTRACT FROM AUTHOR]

Superjunction MOSFETs have been one of the promising switching components for realizing resonant converters. In spite of the numerous studies about the resonant converters in power electronics, the detailed current flow in the device has been still unclear, especially for the inner-current circulation between the body diode and the MOSFET. By employing five-terminals on the superjunction MOSFET, mixed-mode half-bridge resonant converter is simulated. During the turn-on of the MOSFET, the gate charging current flows into the drain-to-source capacitance to form a built-in depletion of the pillars. In the case of the turn-off, the source current reversely flows across the channel with a slightly negative drain-to-source bias and diverts to the gate discharging current.

This paper proposes a single-stage direct AC to high-frequency (HF) AC resonant converter based on LLC configuration for induction heating (IH) systems or HF applications. Unlike conventional converters for IH systems, the proposed topology converts the utility frequency to HF AC in a single stage without using a DC link inductor and capacitors and takes the advantages of LLC configuration. Additionally, it improves the power factor to 0.9–1, lowers the THD (3.2% experimentally), and protects against the high-frequency components. An embedded control scheme was designed to keep the HF current oscillating at a resonant frequency, ensuring zero-voltage switching. The operating principle of the proposed topology was investigated using mathematical equations and equivalent circuits. Finally, it was verified using computer simulation, and an experimental prototype of 1.1 kW was developed to demonstrate the proposed topology’s uniqueness.

This paper proposes a single-stage direct AC to high-frequency (HF) AC resonant converter based on LLC configuration for induction heating (IH) systems or HF applications. Unlike conventional converters for IH systems, the proposed topology converts the utility frequency to HF AC in a single stage without using a DC link inductor and capacitors and takes the advantages of LLC configuration. Additionally, it improves the power factor to 0.9–1, lowers the THD (3.2% experimentally), and protects against the high-frequency components. An embedded control scheme was designed to keep the HF current oscillating at a resonant frequency, ensuring zero-voltage switching. The operating principle of the proposed topology was investigated using mathematical equations and equivalent circuits. Finally, it was verified using computer simulation, and an experimental prototype of 1.1 kW was developed to demonstrate the proposed topology's uniqueness. [ABSTRACT FROM AUTHOR]

When the resonant converters are connected in parallel, the output current is unbalanced without additional current‐sharing measures due to differences in resonant component. In the input‐parallel output‐parallel resonant converter system, the output voltage accuracy of the converter under the traditional droop control is analyzed when the load changes. In this paper, an adaptive droop control is proposed, in which the droop coefficient is adaptively adjusted as the load changes. The control method proposed in this paper realizes the current sharing between the converters and solves the shortcomings of the output voltage changing under different loads in the conventional droop control. Taking two parallel LLC converters as an example, the control block diagram of the parallel control method for adaptive adjustment of the droop coefficient proposed in this paper is given, and the stability of the control loop is analyzed. Finally, two parallel prototypes of LLC converters with input 200 V/output 24 V input are built by digital control, and the experiment shows that the proposed control method improves the shortcomings of excessive output voltage droop caused by traditional droop control during dynamic load switching, which verifies the effectiveness of the method. [ABSTRACT FROM AUTHOR]

To improve the total efficiency of a dual-bridge series resonance converter, a pulse width modulation plus phase-shifted modulation with voltage balance condition is proposed for a hybrid dual-bridge series resonance converter. The control scheme is unified for the whole operating condition and with simple calculation. By employing the proposed voltage balance control, the equivalent unity voltage gain operation can always be achieved, while a simplified two degrees of freedom control can be easily formed. Wide soft-switching range and reduced tank current can be ensured by the pulse width modulation in active hybrid bridge, and power level is adjusted by the phase-shifted modulation. In addition, a magnetizing current compensation method is also employed to improve the soft-switching performance of low voltage side four MOSFETs. The effectiveness of the proposed control is verified by the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents an electric vehicle (EV) switched reluctance motor (SRM) drive with incorporated operation capabilities integrated into the utility grid, the microgrid, and another EV. The motor drive DC-link voltage is established from the battery through an interleaved boost/buck converter with fault tolerance. The varied DC-link voltage can improve driving performance and reduce battery energy consumption over a wide speed range. Through a well-designed current control scheme, speed control scheme, and dynamic commutation tuning scheme, the established SRM drive possesses good performance in the motor driving mode. During deceleration, the regenerative braking energy can be effectively recovered to the battery. When the EV is in idle mode, the grid-to-vehicle (G2V) charging operation can be conducted through the bidirectional switch mode rectifier (SMR) and CLLC resonant converter. Satisfactory charging performance with good line drawn power quality and galvanic isolation is preserved. Conversely, the vehicle-to-grid (V2G) discharging operation can be performed. The EV can make movable energy storage device applications. Finally, the interconnected operations of the developed EV SRM drive to vehicle and microgrid are presented. Through vehicle-to-vehicle (V2V) operation, it can supply energy to the nearby EV when the battery is exhausted and needs roadside assistance. In addition, microgrid-to-vehicle (M2V) and vehicle-to-microgrid (V2M) operations can also be conductible. The EV battery can be charged from the microgrid. Conversely, it can also provide energy support to the microgrid. [ABSTRACT FROM AUTHOR]

A novel single-stage LED driver for street lighting application is proposed in this article which combines a totem-pole boost PFC and a non-isolated LCCL resonant network. The converter offers several benefits, including: appropriate total harmonic distortion (THD) level and high power factor (PF) of the input current; reduced conduction losses and suppressed electromagnetic interference (EMI) thanks to its bridgeless structure; zero-voltage switching (ZVS) for the main switches and zero-current switching (ZCS) for rectifier diodes across the entire input voltage range and load conditions; a constant output current to an LED string load due to the LCCL network characteristic at the resonant frequency; and fixed-frequency operation via the main switches duty cycle for regulating the output current. The paper provides a detailed explanation of the proposed driver operating modes and theoretical analysis, as well as a comprehensive analysis of the impact of parameters on DC-link voltage level and main switches voltage stress. A design procedure is also presented. Experimental verification is demonstrated through a 100W prototype circuit operating at 200 kHz.

LLC converters benefit from soft switching and sinusoidal currents over dual active bridge (DAB) converters. The design process of an LLC converter involves the selection of resonant tank inductor, capacitor, magnetizing inductance, resonant frequency, and transformer turns ratio for proper operation within the desired range of voltages and power. However, the design and control of frequency-modulated LLC converters in wide voltage range applications is challenging due to the wide range of switching frequencies. Topology morphing control is an established technique utilized for countering the challenges of wide voltage range LLC operation. This work provides a design framework for an LLC converter with topology morphing for wide voltage range applications. The proposed design framework uses time domain analysis and a power loss model to evaluate the optimal converter parameters for efficiency maximization over the entire voltage range. Methodology of implementing online topology morphing with closed-loop control in a digital signal processor (DSP) considering an on-board battery charger (OBC) application is also provided. The design optimization process and control methodology are validated through a 300–700 V input, 250–450 V output, 3.3 kW hardware demonstrator. An experimental peak efficiency of 97.72% is achieved compared to a calculated 97.63% efficiency, proving the accuracy of the analytical model. Time weighted averaged efficiency above 96.7% is observed over the entire voltage range.

A novel resonant dc-dc converter with high efficiency and low input current ripple is presented. Without adding any components, the proposed converter significantly improves the efficiency of the conventional half-bridge converter that has input current ripple reduction. By using two input capacitors and two leakage inductances of the conventional converter as resonant elements, a new high-efficiency resonant converter with a double LLC resonant tank is achieved. Consequently, the proposed converter reduces switching losses by the soft-switching operation of all primary switches and secondary diodes in a wide input voltage range. Moreover, it can improve conduction losses by reducing the voltage stress on the secondary diodes. In addition, the output filter inductor is removed, and the ripple and undesired harmonic components caused by the pulsating input current can be significantly reduced without using a large input filter. The operating principle is analyzed, and the experimental results of a prototype verify the feasibility of the proposed converter.

Converters that produce an isolated dc output from a three-phase mains supply are often required. Moreover, input power factor correction (PFC) functionality is essential. A standard two-stage conception with ac/dc and dc/dc converters may be used. However, a single-stage or quasi-single-stage solution can simplify the circuitry and increase efficiency; therefore, many variants of single-stage converters have been researched and published. This paper introduces a novel quasi-single-stage resonant topology with an integrated transformer. Additionally, an original control structure is proposed. This converter enables full control over the output dc voltage and current. Another benefit of the proposed converter is a relatively low complexity of its power circuit and control compared to other single-stage converters. The operation principle of the power circuit is explained and the control strategy is also analyzed in detail. A description of the integrated transformer together with aspects of the resonant circuit design are presented. A simulation of the entire converter was performed and evaluated. Furthermore, a test-bench prototype was designed and constructed and is outlined in this paper. The test-bench measurement results are provided and compared to the simulation results. Power factor and efficiency measurements in terms of their dependence on the output voltage and current are included.

Unfolding-based single-stage ac-dc converters offer benefits in terms of efficiency and power density due to the low-frequency operation of the Unfolder, resulting in negligible switching losses. However, the operation of the Unfolder results in time-varying dc voltages at the input of the subsequent dc-dc converter, complicating its soft-switching analysis. The complication is further enhanced due to the nonlinear nature of the output capacitance ($C_\text{oss}$) of MOSFETs employed in the dc-dc converter. Furthermore, unlike two-stage topologies with a constant dc-link voltage, as seen in high-frequency grid-tied converters, grid voltage fluctuations also impact the dc input voltages of the dc-dc converter in unfolding-based systems. This work comprehensively analyzes the soft-switching phenomenon in the T-type primary bridge-based dc-dc converter used in unfolding-based topologies, considering all the aforementioned challenges. An energy-based methodology is proposed to determine the minimum zero-voltage switching (ZVS) current and ZVS time during various switching transitions of the T-type bridge. It is shown that the existing literature on the ZVS analysis of the T-type bridge-based resonant dc-dc converter, relying solely on capacitive energy considerations, substantially underestimates the required ZVS current values, with errors reaching up to 50%. The proposed analysis is verified through both simulation and hardware testing. The hardware testing is conducted on a 20-kW 3-$\phi$ unfolding-based ac-dc converter designed for high-power electric vehicle battery charging applications. The ZVS analysis is verified at various grid angles with the proposed analysis ensuring a complete ZVS operation of the ac-dc system throughout the grid cycle.

This research presents a multi-channel phase shift inductor-inductor-capacitor (LLC) resonant converter with a wide input and output voltage range that has been specially optimized for fuel cell applications. The worst-case minimum stack voltage and the battery voltage range were used to determine the optimal parameters of the LLC converter. The voltage gain of the converter operating at a constant power was considered, and an algorithm for such a calculation is proposed. Current balancing is implemented using channel temperature measurements, circumventing the need for expensive current sensors. A natural self-balancing mechanism is investigated for converters operating at high frequencies exceeding the series resonance frequency of a resonant converter. Efficiency optimization recommendations for the transformer turn ratio of the converter are illustrated. Multi-object optimization is implemented to achieve an optimized design so that both the minimum and maximum voltage gains can be realized; simultaneously, the transformer turn ratio is kept at a minimum to maintain high efficiency. An experimental prototype of a four-channel converter is implemented and verified at a 5-kW power level. Active content and the C language code files for converter calculations are also provided in this paper.

Usage of ozone is an effective way of treating wastewater, and the silent discharge technique is one of the most efficient and reliable methods for ozone production. Ozone is generated in a Dielectric Barrier Discharge (DBD) chamber through the silent discharge technique and is powered by a high voltage (in the range of -2.5 kV to -5 kV) pulse generator. The pulse generator has two conversion stages, i.e., a high-frequency pre-processing stage and a pulse-frequency post-processing stage. In a high voltage pulse generator, a significant amount of energy from the input is utilised by the converter’s parasitic capacitance and leakage inductance, which reduces the energy delivered to the load for each pulse cycle. This paper proposes an energy-based analysis exploring the potential usage of the flyback converter-based high voltage pulse generator for an application with power requirements under 150W, and water treatment is such an application. An energy-based approach is appropriate to describe the behaviour of the pulse generator in terms of circulating energy and energy exchanges in each stage and energy exchanges between the two stages (i.e. pre and post-processing stages). The proposed analysis is used to derive the essential parameters of the pulse generator and thereby arrive at an appropriate control scheme for the pre and post-processing stages. The proposed energy-based analysis and the derived analytical expressions of the high voltage pulse generator are verified experimentally for a pulsed output voltage of -5 kV having a Pulse Repetitive Rate (PRR) of 1000 Hz and pulse width of $\mathrm {15 ~\mu \text { s} }$ fed from a 12 V battery source.

In this paper, a modified bidirectional CLLC DC/DC converter is proposed to improve the efficiency in wide voltage range applications. The proposed converter adopts a LC series resonant branch parallel with the transformer, so that the equivalent inductance of the parallel branch and the equivalent transformer magnetizing inductor varies with the switching frequency. When the required gain is small and the operating frequency is high, the switch’s turn-off current and the circulating power can be reduced through the large impedance of the LC resonant circuit; When the required gain is large, the switching frequency decreases and the auxiliary branch impedance decreases to obtain a higher voltage conversion ratio. The steady state operation and characteristics of the presented converter are analyzed, a design flowchart and a design example of the modified CLLC are also presented. Furthermore, the model of modified CLLC is established and is reduced for simple analysis. A 48V/400V/800W prototype was built and the experimental results verified the correctness of the proposed converter and the feasibility of the modeling results. Compared with the traditional CLLC resonant converter, the efficiency under wide voltage range application is significantly improved.

Maximum efficiency tracking (MET) with multiple concurrently-activated transmitters (TXs) has not yet been investigated thoroughly. This paper proposes a fast real-time estimation of coupling coefficients and load resistance for multiple concurrently-activated TXs and a moving RX. This is the first paper that demonstrates iteration-less, fast, communication-less MET with power regulation when the RX is moving across multiple activated TX array. The controller senses only the voltage magnitude of TX coil-capacitor resonator, and the input DC voltage and DC current of inverter. Once the parameters are estimated, the controller sets the converters to maximum efficiency point immediately. The benefits of proposed method are that it does not require a communication channel, extra circuit components for MET, time-consuming iterations and computations, and periodic interruption of power flow due to load disconnection or initialization, all of which were limitations in typical methods. Experimental results show that the proposed method provides a fast response (3.8ms) for an RX moving at 6.84 km/h across multiple TXs.

Zero voltage switching (ZVS) of power MOSFETs is essential for resonant converters and the ZVS criterion should be formulated appropriately to achieve the ZVS condition. Conventionally, the energy-based criterion has been considered the most accurate ZVS criterion for non-resonant converters and thus has been directly applied to the resonant converters without any doubt. Through a theoretical investigation along with a few examples, this study shows that the energy-based ZVS criterion is not as accurate for resonant converters as it is for non-resonant converters. A more accurate ZVS criterion, considering energy stored in every energy tank element, the power dissipation of the load, non-zero current assumption at the end of dead time period, and the energy absorbed or supplied by the input dc voltage source, is proposed. The energy-equivalent inductance is introduced to represent resonant tank energy and is used in formulating ZVS criterion for various modulation strategies. In addition, the minimum dead time for successful ZVS transition is also investigated in this study. Experiments have been conducted to validate our new finding and the proposed method is shown to be more accurate than the conventional method.

Summary: In this paper, a new light‐emitting diode (LED) driver based on full‐bridge series resonant converter (SRC) is presented. In the proposed converter LED, load is placed in between DC source and the input side of the full‐bridge inverter which reduces the rectifier components of the SRC. The proposed converter reduces the number of diodes used for rectification and ensures zero voltage switching of the power switches which improves the efficiency of the converter. LED lamp current is regulated with phase‐shift pulse width modulation (PWM) of full‐bridge. Lamp illumination is controlled with PWM dimming. The operation and mathematical analysis of LED driver is presented. To validate the proposed concept, a 40‐W laboratory prototype is developed. Experimental results are presented. Peak efficiency of 93% is obtained. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

In the paper, a discrete dynamic model of a full-bridge resonant converter with a symmetrical operating mode has been obtained, which describes the resonant converter as a transfer link with an supply voltage input side and a load current output side. The dynamic model is based on a linear mathematical model of the resonant converter built according to the superposition principle. The structure of the resonant converter with the processes outline function is given and analyzed. The structure of the discrete dynamic model of the resonant converter of the nth order is presented. It is proved that the transfer function of the discrete dynamic model for the outline function can be determined by the transfer function of the continuous system. The resulting dependencies describing the discrete transfer functions of the resonant converter are used to obtain the discrete dynamic model of the double-circuit transformer resonant converter in a synchronous rectifier. For this, the sequence of actions is defined: definition of the transfer function of the continuous dynamic model; obtaining the system of equations in vector-matrix form describing electromagnetic processes in the converter; definition of the system of discrete equations; definition of the transfer function of the circuit. The obtained theoretical results were verified by means of simulation modeling of the considered double-circuit resonant converter. The proposed dynamic model makes it possible to analyze the influence of instability and low frequency fluctuations of the supply voltage of the resonant converter on the output values. The presented results can be used in the development and improvement of single- or multi-circuit bridge high-frequency resonant converters as the secondary power sources and converters used in ship demagnetization systems. References 25, figures 8, tables 2. [ABSTRACT FROM AUTHOR]

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In this paper, a three-phase single-stage AC-DC converter for an IPT-based small wind power generation system (WPGS) with an S-S compensation circuit is proposed. It applies a three-phase single-stage AC-DC converter to improve the input power factor (PF), efficiency, and reliability in small WPGSs. Also, inductive power transfer (IPT) was applied to compensate for brush wear in the nacelle of small and medium-sized wind turbines while ensuring electrical safety. In conditions of the three-phase Permanent Magnet Synchronous Generator (PMSG) voltage (80~260 Vrms) for the wind turbine and the load (150~1000 W), it was verified that the desired output voltage below 3% can be controlled through the fixed link voltage (VLink) control without wireless communication. A 1 kW prototype was built and tested to demonstrate its applicability to the rotation of small and medium-sized wind turbine nacelles instead of brushes and slip rings.

Ultrasonic transducers (UTs) are the main components for generating sonic waves. These types of transducers are nonlinear loads, and they are adversely affected by changes in mechanical load or temperature. UTs are operated in the region close to the resonant frequency. An ultrasonic transducer needs to be driven by a high-frequency inverter. In this paper, a Class D resonant inverter circuit is implemented for ultrasonic mixer application. The proposed circuit operates at 34306 Hz at 140 V and has low cost and size. The simulation results of Class D inverter verified with the prototype experimental circuit. Al (Aluminum) alloy with ethanol and graphene is mixed in order to show the mixing performance of the resonant inverter fed transducer with probe. The system achieved the fine particles and homogen mixture according to the SEM images and EDX analysis.

The original system, designed as a combination structure of a linear machine and a wireless power transmission transformer, was designed to overcome the limitations of the wired power supply method used for working robots and transportation equipment in existing smart factories, and improvements in magnetic coupling and power transfer efficiency are needed. In this work, we study the efficiency improvement of a system that can supply wireless power to track-type transportation equipment. For this purpose, electromagnetic properties such as magnetic equivalent resistance, inductance, magnetic coupling rate, and core loss are analyzed using the finite element method. In addition, the results of magnetic field finite element analysis are applied in electrical equivalent circuit modeling to analyze the voltage transfer ratio and input/output characteristics of a CLLC resonant converter designed for wireless power transmission. The efficiency improvements of the proposed model are verified through a comparison of experimental and simulation results after fabricating a prototype. From the results of this study, a more optimized wireless power transmission system design based on the analysis results from an electromagnetic perspective can be realized to improve the efficiency of wireless power transmission. [ABSTRACT FROM AUTHOR]

This paper presents a new control method for a bidirectional DC–DC LLC resonant topology converter. The proposed converter can be applied to power the conversion between an energy storage system and a DC bus in a DC microgrid or bidirectional power flow conversion between vehicle-to-grid (V2G) behavior and grid-to-vehicle (G2V) behavior. Furthermore, such a converter can be applied to energy storage systems for decentralized renewable energy generation systems, such as solar and wind power. In addition, this converter can be combined with a bidirectional inverter to allow energy storage in the system to improve the safety, stability, and power quality of the microgrid. In the proposed circuit structure, we use a bidirectional DC–DC LLC, which has the advantages of a higher voltage conversion ratio, lower part count, simpler control than similar converters such as DAB, CLLC, and L–LLC converters, and bidirectional power flow and electrical isolation. Specifically, to extend the battery life, it can be employed as a control strategy for discharging the energy stored in the battery (SOC) and reducing the temperature rise generated by the internal solid electrolyte interphase (SEI) when discharging the battery under the variation in distributed energy resource (DER) generation and load demand. To realize the bidirectional power conversion without using any auxiliary inductor and only changing the control strategy, the forward step-down power conversion was based on pulse frequency modulation (PFM) control, and the reverse step-up power conversion was based on pulse width modulation (PWM) control. In this paper, we introduce the bidirectional converter topology and its control strategy for the DC microgrid battery energy storage system. Finally, a 500 W prototype is built to verify the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

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This paper describes a resonant Dickson-based topology that achieves complete soft-charging with two-phase operation and a convenient 50% duty cycle at all odd conversion ratios. A brief analysis is presented that shows how the resonant switching frequency can be calculated as a function of inductor and capacitor values. One solution sets all capacitors and both inductors equal, and results in switching devices experiencing a constant blocking voltage that is largely independent of load and fly capacitor voltage ripple. The requirement for capacitor matching and subsequent low capacitance density C0G dielectrics is compensated by a weakly bounded voltage swing: no switching devices are present on intermediary nodes connecting L and C elements allowing for very large voltage ripple and highly effective utilization of each fly capacitor's energy density. A discrete 1:5 prototype validates the proposed topology with measured waveforms illustrating 50% two-phase operation and a load-independent maximum blocking voltage across switching devices. An output power of 129 W with a 94% peak efficiency was measured for an input voltage of 20 V. Measuring 11.45 mm × 12.95 mm × 2.8 mm, this prototype achieves a very high power density of 311 kW/liter (5, 096 W/inch3) despite the use of diodes for simplicity and 66% of the converter's volume being comprised of PCB and free space.

This paper presents an electric vehicle (EV) switched reluctance motor (SRM) drive with incorporated operation capabilities integrated into the utility grid, the microgrid, and another EV. The motor drive DC-link voltage is established from the battery through an interleaved boost/buck converter with fault tolerance. The varied DC-link voltage can improve driving performance and reduce battery energy consumption over a wide speed range. Through a well-designed current control scheme, speed control scheme, and dynamic commutation tuning scheme, the established SRM drive possesses good performance in the motor driving mode. During deceleration, the regenerative braking energy can be effectively recovered to the battery. When the EV is in idle mode, the grid-to-vehicle (G2V) charging operation can be conducted through the bidirectional switch mode rectifier (SMR) and CLLC resonant converter. Satisfactory charging performance with good line drawn power quality and galvanic isolation is preserved. Conversely, the vehicle-to-grid (V2G) discharging operation can be performed. The EV can make movable energy storage device applications. Finally, the interconnected operations of the developed EV SRM drive to vehicle and microgrid are presented. Through vehicle-to-vehicle (V2V) operation, it can supply energy to the nearby EV when the battery is exhausted and needs roadside assistance. In addition, microgrid-to-vehicle (M2V) and vehicle-to-microgrid (V2M) operations can also be conductible. The EV battery can be charged from the microgrid. Conversely, it can also provide energy support to the microgrid.

In order to demonstrate the performance of an LLC resonant converter with digital control, in this paper, we analyze the operating principles of the full-bridge LLC resonant converter. According to the operating characteristics of the full-bridge LLC resonant converter at different frequency bands, a simulation model was established using MATLAB Simulink software, and simulations were carried out. The digital control system of full-bridge LLC resonant converter was then designed based on the STM32 microcontroller. The simulation and experimental results demonstrated that the LLC resonant main circuit was always operating within the zero voltage switching (ZVS) state of the primary MOSFET and the zero current switching (ZCS) state of the secondary rectifier diode, while soft-switching was achieved in the full load range. The digital control of the full-bridge LLC resonant converter was ideally realized based on STM32. The input disturbance load test result validated the closed-loop concept of the proposed LLC resonant converter. The step response results in both simulation and load tests show that the power supply system has the desired dynamic response characteristics with low overshoot, short rise time and settling time, while the load step response results in both tests showed that the system has a strong anti-interference ability and robustness. [ABSTRACT FROM AUTHOR]

This work presents the experimental validation of a 40 kW electric vehicle (EV) charger. The proposed system comprises two 20 kW modules connected in parallel at the input and output. Each module has two stages—as a grid converter Vienna Rectifier (VR) was chosen, and as an isolated DC/DC stage, two Series-Resonant Dual-Active-Bridges (SRDABs) in input-series-output-parallel (ISOP) configurations were applied. The AC/DC and DC/DC stages were enclosed in 2U rack standard housing. A bipolar DC-link with ±400 V DC voltage was employed to connect both stages of the charger module while the charger's output is dedicated to serving 800 V batteries. VRs operated at 66 kHz switching frequency and the SRDABs operated at 100 kHz. The converters used in the charger structure were based on silicon carbide (SiC) power devices. The description and parameters of the built hardware prototypes of both—AC/DC and DC/DC—converters are provided. Moreover, the experimental validation of each stage and the whole charging system, including oscilloscope waveforms and power analyzer measurements at nominal power, are included. Such a configuration enables energy conversion with high efficiency without a negative impact on the grid and high-quality grid waveforms. [ABSTRACT FROM AUTHOR]

The main contribution of this paper is the inductive compensation of a wireless inductive power transmission circuit (IPT) with resonant open-loop inductive coupling. The variations in the coupling coefficient k due to the misalignment of the transmitter and receiver are compensated with only one auxiliary inductance in the primary of the inductive coupling. A low-power prototype was implemented with the following specifications: input voltage Vin = 27.5 V, output power Po = 10 W, switching frequency f = 500 kHz, output voltage Vo = 12 V, transmission distance d = 1.5 mm. Experimental results varying the distance "d" with several values of the compensation inductor demonstrate the feasibility of the proposal. An efficiency of 75.10% under nominal conditions was achieved. This proposal is a simple compensation topology for wireless chargers of cellular phones presenting small distances between the transmitter and receiver. [ABSTRACT FROM AUTHOR]

Summary: Very‐high‐frequency (VHF) resonant converters have the advantages of small volume, light weight, and high power density. However, under the operating frequency of tens of megahertz, the nonlinear characteristics of the power semiconductor devices intrinsic capacitances will affect the analysis accuracy of VHF converters and increase the difficulty of parameter design of these converters. Thus, this paper proposes a method to obtain the equivalent capacitances of power semiconductor devices. Taking the VHF resonant boost converter as an example, the process of obtaining the equivalent capacitances of power semiconductor devices is elaborated first. And then a prototype with operating frequency 17.30 MHz, input voltage 3–6 V, and output voltage 9–18 V is built to verify the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

By applying resonant charge redistribution (RCR) to the parasitic capacitances of a switched-capacitor converter, COSS-related dynamic switching losses can be significantly reduced. The proposed technique demonstrates adiabatic mitigation of all primary loss mechanisms in a transformer-less resonant Cockcroft-Walton (CW) converter's forward power path, with only the gate drivers exhibiting conventional hard-charged CV2f losses. Two inductors are used: a large primary inductance directly in the forward power path to mitigate transient inrush currents, and a second small inductance to perform Coss charge redistribution prior to initialization of subsequent phases. The second inductor can be small while still exhibiting high Q-factor as it only interacts with switch parasitics. A discrete 1:5 prototype using GaN-FETs and diodes achieves a power density of 181.8 kW/liter (2.98 kW/inch3) and a peak efficiency of 96.2% with RCR contributing a measured 61% reduction in total losses at light load for a 0.74% increase in solution volume.