Additional Induction Research Articles

Double-Sandwich Magnetic Coupling Structure Design for Dual-LCL Wireless Charging System in EV Applications

In the wireless charging system of EVs, the traditional single-stage LC resonance network has the issues of narrower of parameter design and small equivalent input impedance. While the composite resonant network will introduce additional resonant capacitors and inductors, which increases the system volume, cost, and reduces the efficiency. This paper proposes a design scheme of double-sandwich magnetic coupling structure with a low cross-coupling coefficient, which integrates the resonant inductors into the power transmitter and receiver, and it is designed taking the magnetic leakage and loss as constraints. A 500W prototype is built, and the comparison of experimental efficiencies between the double-sandwich and the separate magnetic coupling structures is performed. Finally, the effectiveness of the integrated design scheme is validated.

Time-domain Dynamic-performance-improvement Method for Pulse-width-modulated DC-DC Converters Based on Eigenvalue and Eigenvector Sensitivity

For pulse-width modulated (PWM) DC-DC converters, the input voltage fluctuation and load variation in practical applications make it necessary for them to have better dynamic performance to meet the regulation requirements of the system. The dynamic-performance-improvement method for PWM DC-DC converters is mainly based on indirect dynamic performance indices, such as the gain margin and phase margin. However, both settling time and overshoot in the time domain are important in practical engineering. This makes it difficult for designers to obtain a clear understanding of the time-domain dynamic performance that can be achieved with improved control. In this study, a direct analysis of the time-domain dynamic characteristic of PWM DC-DC converters is performed. A dynamic-performance-improvement method based on eigenvalues and eigenvector sensitivity (E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> S-based DPIM) is proposed to directly improve the time-domain dynamic performance index of PWM DC-DC converters. By considering a boost converter with proportional-integral control as an example, an additional virtual inductor current feedback control was designed using the proposed dynamic-performance-improvement method. Simulation and experimental results verify the validity and accuracy of the proposed dynamic-performance-improvement method.

High-Order Compensation Topology Integration for High-Tolerant Wireless Power Transfer

Wireless power transfer (WPT) has been a promising way to transfer power wirelessly over certain distances through the mutual inductance (MI) of the magnetically coupled transmitter and receiver coils, providing significant benefits of convenience, safety, and feasibility to special occasions. The stable output and efficiency cannot be maintained due to the load variation and the inevitable misalignment between the magnetic couplers. High-order compensation topologies that are highly flexible in design due to more compensation elements are essential for the WPT to suppress the load variation and misalignment effects. However, due to core loss and thermal management, high-power-level and high-frequency inductor design have always been challenging for WPT systems. Space occupation and cost are other aspects to be considered for inductor design. Thus integrating these additional bulky inductors into the main coils has been a critical trial. As a result, the compensation topologies’ original input and output profiles will change or even disappear. This paper reviews the existing high-order compensation topologies and their integration principles and implementation for the WPT to obtain high misalignment tolerance. The design objectives and challenges of the integrated compensation topology in terms of misalignment tolerance capability are discussed. The relevant control systems to cope with coil misalignment and load variations are investigated. Challenges and future development of the high-tolerant WPT are discussed.

Multilevel Switched Capacitor LLC-DCX Converter With Embedded Filter

A multilevel switched capacitor LLC-DC transformer (LLC-DCX) converter with an embedded filter is presented for a power module of solid-state transformers. The proposed converter is a hybrid converter composed of resonant switched capacitor converters (RSCCs) and a previously reported ripple-cancel converter. In contrast to the conventional SCC, which faces the issue of an inrush hard-charging current during switching transition, the proposed converter can be implemented using a soft-charging operation without additional inductors. Further, it inherits the advantages of the two converters, including load-independent soft switching, automatic voltage sharing, automatic current sharing, reduction of the current ripple, an embedded filter function, constant voltage gain, and flexible extensibility. This paper comprehensively analyzes these characteristics and the conditions for soft-charging operation. The design theory based on the analysis is also presented. We fabricated a prototype of the proposed converter with input and output voltages of 900 V and 150 V, respectively and the rated output power of 2 kW to demonstrate the validity of the analysis and design.

PCB Winding Coupled Inductor Design and Common-Mode EMI Noise Reduction for SiC-Based Soft-Switching Three-Phase AC–DC Converter

This article presents a PCB winding coupled inductor design for both high efficiency and effective common-mode (CM) noise reduction in a silicon carbide (SiC)-based soft-switching three-phase ac–dc converter. A balance technique is applied to reduce the CM noise, creating a return path with additional inductors. The inductors in the main circuit and return path are coupled in one core and implemented with PCB windings. A winding interleaving structure with strong coupling between the main inductors is selected to minimize the winding loss and to improve the converter efficiency; however, the interwinding capacitance brought on by the winding interleaving worsens the CM noise. An inductor model including the capacitance is introduced, and its impact on the CM noise is analyzed. A novel inductor structure is proposed to scale back the interwinding capacitance and to enhance the CM noise reduction capability. Experiments with a SiC-based 25-kW soft-switching three-phase ac–dc converter prototype validates the performances of the proposed PCB winding coupled inductors.

High Precision Primary Side Regulation Constant Voltage Control Method for Primary and Secondary Resonant Active Clamp Flyback Converter

Active clamp flyback (ACF) converter has been demonstrated that which is better than traditional flyback in high-frequency power-adaptor applications. According to the circuit structure, ACF has two modes, primary resonant ACF (PR-ACF) and secondary resonant ACF (SR-ACF). In order to improve the power density, a high-precision primary side regulation (PSR) constant voltage control method for ACF converter is proposed in this article. The proposed method not only can be effectively adopted in PR-ACF but SR-ACF converter. The high-precision output voltage is predicted by highly accurate sampling points on primary auxiliary voltage. The applied microcontroller environment improves the practicability and increases the power density of the ACF system. To verify the proposed PSR method, a prototype that can be changed into PR-ACF and SR-ACF is designed. The output voltage offset, operation efficiency, and dynamic performance are analyzed. The tested results show that high-precision output is obtained in ACF converter by using the proposed method and the maximum output voltage deviation which are 4% and 3.5% in PR-ACF and SR-ACF converter, respectively. Moreover, SR-ACF has a higher efficiency compared with PR-ACF converter, and a smaller voltage shoot during dynamic process, which needs a larger regulation time since the additional output inductor.

A multi-functional converter based switched reluctance motor drive for electric vehicle

&lt;span&gt;Owing to the resilience and ease of control, switched reluctance motors are commonly utilized in electric vehicle drives. This paper provides a topology for a multi-functional power converter for switched reluctance motor based electric vehicle drive with driving, braking and charging potentialities. With efficient control algorithms, a single power electronic converter is used for motoring, regenerative braking, and charging of the battery bank, resulting in a cost-effective power electronic interface. The front-end voltage control and current control of the switched reluctance motor (SRM) are used to achieve open loop and closed loop speed control during driving mode. Re-generation is made possible through restricted switching of phases in negative torque region. A bridgeless rectifier converter is built in battery charging mode by combining the SRM's two-phase windings with the prevailing power devices of an integrated power converter, eliminating the need for additional inductors and charging units. Simulations are run in MATLAB/Simulink, and simulation results are used to validate the control schemes for all modes.&lt;/span&gt;

Phase‐shifted full‐bridge converter based on an adjustable current auxiliary circuit with full load range ZVS and small duty cycle loss

AbstractIn this paper, a phase‐shifted full‐bridge converter based on an adjustable current auxiliary circuit is proposed. The converter's switches achieve ZVS with the help of the parallel current provided by the auxiliary circuit. The conduction loss of the parallel current is reduced since the magnitude of the current can be adjusted by the variable inductor. Since there is no additional series inductor, the duty cycle loss of the proposed converter is minimal. Moreover, the oscillating voltage on the secondary side decays quickly, indicating that the energy involved in the oscillation is small, which is beneficial to reduce the loss of the RCD. The experimental platform is built. On this basis, theoretical analysis and experimental verification are carried out in this paper.

More Enhanced Swing Colpitts Oscillators: A Circuit Analysis

In this paper, we show that an additional inductor–capacitor–inductor filter can increase the oscillation amplitude of the enhanced swing Colpitts oscillator (ESCO), and call this topology the more enhanced swing Colpitts oscillator (mESCO). When it is connected with a rectifier, the DC–DC boost conversion ratio can be increased, especially for low-voltage sensor ICs or energy harvesting. This paper focuses on the electrical characteristics of mESCO. The oscillation frequency was modeled as a function of the circuit parameters of mESCO. The common gate voltage gain (ACG), defined by the ratio of the drain voltage amplitude to the source voltage amplitude of the switching MOSFET of mESCO, was also modeled under the assumption that all the circuit elements are ideal. The model was validated with a SPICE simulation. For ACG &lt; 1.5, the model was in good agreement with the SPICE results within 10%. In addition, the drain voltage amplitude vda was modeled by assuming that the average transconductance of the MOSFET in a half cycle is null when the long-channel Shockley model is used. vda needs to be sufficiently high to have a large DC–DC boost conversion ratio. The model can predict the tendency that vda increases as ACG approaches unity. We found that the voltage difference of the drain voltage amplitude to the source voltage amplitude is a constant even when the circuit parameters, and thereby ACG are varied.

Primary-Side Linear Control for Constant Current/Voltage Charging of the Wireless Power Transfer System Based on the LCC-N Compensation Topology

This article proposes a primary-side linear control strategy to realize the constant current (CC)/voltage (CV) charging for the wireless power transfer system, based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-N</i> magnetic integration and non-compensation circuit. Different from the conventional compensation topology used in control strategies, this article combines magnetic integration structure on the primary side and noncompensation topology on the secondary side, which reduces the size of the additional compensation inductor and makes the secondary side more compact. Moreover, the primary-side linear control strategy is studied by using the improved load parameters identification method, based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-N</i> topology. First, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-N</i> magnetic integration and noncompensation topology is introduced. An improved load parameters identification method considering the non-pure resistive input impedance characteristics of the rectifier is proposed to identify the current, voltage and equivalent resistance of the load, based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-N</i> topology. In the process of identification, the complicated relationship between the input impedance of the rectifier and the load is needless. Then, according to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC-N</i> output characteristics and identified load parameters, the relationship between the input voltage and load current and voltage is simplified to linear through the linear superposition of fundamental wave and third harmonic. And a linear control strategy on the primary side is proposed to achieve CC/CV output. Finally, a 1 kW WPT prototype is built to verify the effectiveness of the proposed control strategy. The experimental results show that the maximum error of the output current is 1.8% during the CC charging, and the maximum error of the output voltage is 1.2% during the CV charging.

Design of a Modified Single-Stage and Multistage EMI Filter to Attenuate Common-Mode and Differential-Mode Noises in SiC Inverter

The SiC inverter switching at high frequencies introduces increased common-mode (CM) and differential-mode (DM) electromagnetic interference (EMI) issues, such as shaft voltage, bearing currents, insulation degradation, and poor current quality in the motor. These EMI issues are commonly addressed with EMI filters employing CM and DM inductors. The increased volume and poor performance of a CM inductor designed for SiC inverter switching at high frequency require a modified EMI filter design procedure for enhanced performance and volume minimization. In this work, three EMI filters are presented with modified design procedures. A single-stage EMI filter is designed by incorporating a DM filter offering an equal attenuation to DM and CM noise at switching frequency. Here, the additional CM attenuation demand is fulfilled by a marginal value of the CM inductor, while, in multistage EMI filters, the required CM attenuation is split between the two stages. The multistage EMI filter 1 is designed using an additional CM inductor and existing load capacitance as the second stage, whereas the multistage EMI filter 2 is designed with a lesser value of CM inductance to provide CM attenuation over the entire conducted EMI frequency range. The modified EMI filters are tested on an SiC inverter operating at 200 kHz.

Dual-Active-Half-Bridge Converter With Output Voltage Balancing Scheme for Bipolar DC Distribution System

Conventional dual-active-bridge dc–dc converters require a dedicated voltage balancer or feedback control when they are used for a bipolar LVdc distribution system. This article proposes a dual-active-half-bridge (DAHB) converter with voltage balancing. The proposed converter is composed of a conventional DAHB converter with an additional inductor and capacitor voltage balancer (LCVB). The LCVB is added between the transformer and the output of the DAHB converter. Although the LCVB increases the switch current, it can balance the two output voltages without additional active switching device and feedback control under unbalanced load conditions. In addition, compared with the conventional DAHB converter, the LCVB can increase the zero-voltage-switching range of the DAHB converter and has no detrimental effect on the operation modes and performances. A 2.8-kW prototype was built and tested to verify the performances of the proposed converter.

High Efficiency Integrated Transformer Design in DAB Converters for Solid-State Transformers

Solid-state transformers (SST) are emerging technologies to replace the conventional low-frequency main transformer (MTR) in railway vehicles. In order to isolate the load side from the AC 25 kV high-voltage (HV) side and to reduce the whole size of the SST, HV insulation and high-frequency transformers should be used in DC/DC converters. Furthermore, due to the severe constraint of installation space and difficulty of heat dissipation management in the bottom of railway vehicles, high-power density and minimum transformer loss should be considered. To satisfy such design requirements of the proposed SST for railway vehicles, high efficiency integrated transformers, which inherently have leakage inductance, are proposed for dual-active-bridge (DAB) converters in this paper. In order to obtain appropriate equivalent leakage inductance for the DAB converters, a calculation methodology for the leakage inductance has been introduced and verified by simulation. Two separated winding structures in the center-core are adopted to improve the core loss, and appropriate winding turns with 60 kV HV insulation capability are selected, according to the proposed design procedure of the integrated transformers. In order to compare the proposed transformers with the conventional transformer having additional inductors and to verify the major characteristics of the transformers, two 125 kW proposed transformers and conventional transformers have been built and evaluated by an 250 kW SST module, operating at 10 kHz switching frequency. Under a 125 kW full-load condition, 99.7% transformer efficiency was obtained by the proposed integrated transformers, which are 4.7% smaller and 7.0% lighter than the conventional transformer. As a result, 26°C maximum temperature improvement has been obtained and 60k V HV insulation capability has been satisfied by the proposed integrated transformers.

A Novel Topology for Solar PV Inverter Based on an LLC Resonant Converter With Optimal Frequency and Phase-Shift Control

In this article, a new topology for a grid-connected solar photovoltaic inverter for the direct connection to the medium-voltage grid is proposed. This topology employs an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with a high-frequency (HF) isolation transformer in the dc–dc stage. The output of the dc–dc stage is a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this dc stage and the grid. A combined phase-shift and frequency control method is used to control the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter. The phase-shift angle and switching frequency values of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter are regulated to track the reference current signal for the whole operation range. The Lagrange multiplier method is applied to find the optimal trajectory to calculate the optimal phase-shift angle and switching frequency pairs for any operation condition by considering power converter and HF transformer losses to achieve the highest efficiency at a varying current. The transformer leakage and magnetization inductances are properly designed to provide a zero-voltage switching (ZVS) for a wide operation area, and additional resonant inductor requirement is removed. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter operates in a ZVS region except in a narrow band around the zero-current crossings of the inverter output. Using an HF transformer in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter, a bulky line frequency transformer requirement is eliminated, and thus, a more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results.

A SERIES RECONFIGURABLE STRUCTURE RESONANT CHOPPER FULLY SOFT-SWITCHED DUAL-ACTIVE-BRIDGE WITH DUAL TANK

Compared to the dual-active-bridge converter, the Double-bridge arrangement thunderous converter (DBSRC) can extend delicate exchanging run. To encourage broaden the soft-switching extend and progress the circuit execution, a modern DBSRC with double tank based on DBSRC is proposed in this paper. This modern converter highlights two thunderous tanks and a tapped transformer, and it can perform superior than the DBSRC by optimized tap coefficient x of the tapped transformer. Its operation guideline, voltage pick up, the soft-switching characteristics, and yield control are analyzed in detail, and compared with the DBSRC. Comes about appear that the pro-posed dual-tank topology has displayed higher voltage pick up, more extensive soft-switching locale, and bigger yield control than the conventional DBSRC when the tap-coefficient x is chosen sensibly. DC-to-DC bidirectional resounding converter to be utilized for bidirectional control exchange applications particularly battery charging discharging applications in electrical vehicles. Its similar to an LLC resonant converter, but on the secondary side of the circuit, an additional inductor and capacitor have been added to make the resonant network symmetric for operation in both forward and backward directions. The switches in the inverting step have zero voltage switching (ZVS). Under ZCS, the rectifier diodes on the secondary side also turn off. ZVS and ZCS reduce losses and enable high-frequency operation, resulting in smaller magnetic elements and filter capacitors, lowering size, weight, and volume while enhancing power density. INDEX TERMS—dual active bridge (DAB), dual-bridge series resonant converter (DBSRC), soft-switching, dual-tank, tapped- transformer, tap-coefficient

Improved Positive Output Voltage Super-lift Boost Converter

Starting from the positive output voltage-lift Boost converter, which has a higher voltage transformation ratio and reduced voltage stress across the semiconductors, the additional losses caused by the periodic recharging of the intermediate capacitor are analyzed. An additional inductor improves the efficiency of this converter. The dimensioning of this improved converter, its dynamic behavior, the inrush-current and a feed-forward control are treated. The considerations are supported by simulations.

A Push–Pull Series Connected Modular Multilevel Converter for HVdc Applications

This article introduces a push–pull series connected (PPSC) ac–dc converter intended for high-voltage direct current applications. The proposed topology requires fewer submodules compared to a standard modular multilevel converter (MMC) to withstand the same dc voltage. Each converter phase unit is connected to its corresponding phase on the ac side via a center-tapped single-phase transformer which also provides the galvanic isolation needed in most applications. The required arm inductance can be merged into the transformer leakage inductance avoiding the need for additional inductors. In this article, both the design and operation of the converter are discussed in detail. Furthermore, a comparison of the PPSC and MMC in terms of energy storage requirements and efficiency is presented. The converter concept and the control strategy proposed is validated by computer simulations using the piecewise linear electrical circuit simulation (PLECS) simulation package as well as through experiments on a small-scale, 300-V, 2-kW laboratory prototype.

Balance Techniques and PCB Winding Magnetics for Common-Mode EMI Noise Reduction in Three-Phase AC–DC Converters

In this article, balance technique is applied into two-channel interleaved three-phase ac–dc converters with critical conduction mode based soft switching modulation. By adding additional inductors and coupling them with the original ones, the realization of the balance becomes possible with proper design; thus reducing the common-mode (CM) EMI noise. The balance condition is derived, and the impact of balance technique on the circuit operation especially on the switching frequency variation is quantified in order to provide the design guideline. Based on the application of balance technique, instead of the commonly used litz-wire-based inductors, PCB winding coupled inductors are adopted and designed to effectively achieve the reduction of CM EMI noise. The design methodology and process are presented, and the design tradeoff is made between the inductor loss and the inductor footprint. Finally, the effect of CM EMI noise reduction and the system efficiency with balance techniques and PCB winding magnetics are tested on a 25-kW silicon-carbide-based soft-switching three-phase ac–dc converter prototype.

Analysis and design of a wide range ZVS/ZCS push–pull DC/DC converter with voltage clamped

A new isolated zero-voltage switching (ZVS)/zero-current switching (ZCS) push–pull (PP) DC/DC converter is presented. One auxiliary switch S3 and a clamping capacitor Cc are introduced at the primary of the conventional push–pull converter and a voltage doubler-rectifier is adopted on the secondary side. This proposed converter has the features: (1) Switching losses are reduced significantly owing to zero-voltage switching of primary switches and zero-current switching of secondary diodes over a wide load range variation. (2) The voltage spike across all of the power devices can be clamped that enable the use of low-voltage, low-performance, and lower-cost devices. (3) The energy stored in the transformer leakage inductance is used for the soft-switching action and no additional resonant inductor is required. (4) A voltage doubler-rectifier is employed to remove the problem of the diode reverse-recovery effect and reduce the duty cycle loss that provides a much higher voltage conversion ratio. These merits make this simple converter provide an attractive solution for a distributed power system, uninterruptible power system, or battery charge/discharge system. The detailed operation, analysis, design, comparative study, and experimental results for the proposed converter are presented and a 600 W prototype was developed to verify the discussed theoretical analysis.

A Flyback Converter With Novel Active Dissipative Snubber

The active clamp flyback converters (ACF) can provide features of high power density and high power efficiency. However, ACF is usually applied to in the applications of medium-to-high power range. For a low power application, the ACF may not be a cost-efficient choice. The flyback converter with a lossless snubber can provide high efficiency for low-power application, but it needs an additional inductor and generates more electromagnetic interference (EMI) emissions. The circuit designers also consider the balance between conversion efficiency, size, and cost. Based on the reasons above, the flyback converter with dissipative RCD snubber is still popular in the applications of low-to-medium power range. When the dissipative snubber is adopted to reduce EMI in the power converters, it increases the loss and hence reduces the efficiency. In this paper, a new concept, called active dissipative snubber, is proposed to suppress the resonance in the discontinuous conduction mode (DCM). In the proposed active dissipative snubber, the digital controller activates the dissipative snubber only when the EMI noise is occurring, then disabled after the noise is decayed or disappears. Digital logic makes the passive snubber smart, which can selectively absorb the EMI noise. Since the proposed snubber is not connected to the main circuit all the time, it can provide lower power loss, but still performs better EMI emissions and maintains conversion efficiency.