Bridge Leg Research Articles

A Hybrid Desaturation Fast Detection Circuit for Bridge Leg Short-Circuit Faults

A Hybrid Desaturation Fast Detection Circuit for Bridge Leg Short-Circuit Faults

Efficient Hybrid Dual Full-Bridge DC–DC Converters for Pulsed Output Current Applications

This paper presents a hybrid full-bridge DC-DC converter for a wide output voltage range in high efficiency, especially for pulsed output current applications. For the conventional phase-shift-full-bridge DC-DC converter, the hard switching and circulating current lower the efficiency in the wide output conversion ratio. To improve the efficiency of the DC-DC power supply for the pulsed output current, a hybrid DC-DC converter is proposed. On the primary side, two full bridges are integrated by sharing a bridge leg. The circuit on the secondary side is a hybrid rectifier stage. For the pulsed output current with a constant load resistor, a single full bridge works in the low output current. For the large output current, the hybrid two full bridges work together. The circulating current in the hybrid working mode is reduced by a blocking capacitor. The converter is controlled by the phase shift and duty cycle control. All the switches work in zero voltage switching. A prototype is built to verify the performance and control strategy of the converter.

Hybrid-Level Modulation Scheme for Dual-Bridge Series-Resonant Converter

This paper proposes a hybrid level modulation (HLM) scheme to achieve full load range zero voltage switching (ZVS) over various voltage gains for dual-bridge series-resonant converter. According to the load conditions, HLM includes two parts. At heavy load, a variable-frequency symmetrical level modulation (VFSLM) scheme is offered to ensure the complete commutation of the bridge legs with soft-switching operation. In addition, the optimal root mean square (rms) of the inductor current can be achieved, which further benefits the transfer efficiency. At light load, the switching frequency demanded by VFSLM is much higher than the resonant frequency. So, a dual asymmetric level modulation (DALM) scheme is proposed to prevent devices from hard-switching operation within a moderate range of changes in frequency. Furthermore, the method of identifying control variables with DALM is analyzed for overall efficiency optimization. The developed approach is validated on a 6.6kW on-board-charger whose output voltage varies from 220V to 470V.

All‐SiC 99.4%‐efficient three‐phase T‐type inverter with DC‐side common‐mode filter

AbstractThis letter presents a hardware demonstrator of an all‐SiC three‐level T‐type (3LTT) inverter with the common‐mode (CM) EMI filter stages placed on the DC input instead of the AC output side, targeting, for example, high‐efficiency PV applications. The extensive experimental characterization shows that state‐of‐the‐art SiC transistors and a DC‐side CM filter enable an unprecedented peak/full‐load efficiency of 99.4% (calorimetric measurement) at 12.5 kW and a power density of 2.4 kW/dm3(39 W/in3). The demonstrator fulfills CISPR 11 Class A EMI regulations as well as upcoming EMI standards for the frequency range of 9–150 kHz. Compared to other high‐efficiency converters, which often employ bridge legs with more output voltage levels, the described 3LTT concept thus offers a very favorable trade‐off between complexity and performance.

Three-Leg Quasi-Z-Source Inverter with Input Ripple Suppression for Renewable Energy Application

Single-phase inverters are widely employed in renewable energy applications. However, their inherent 2ω-ripple power can substantially affect system performance, leading to fluctuations in the maximum power points (MPP) of photovoltaic (PV) systems and shortening the lifespans of fuel cell (FC) systems. To alleviate input ripple, a three-leg quasi-Z-source inverter (QZSI) and its associated control strategy are proposed. The QZSI consists of a quasi-Z-source network, an H-Bridge inverter, and an active power filter (APF). The active filtering structure comprises filtering capacitors and the third bridge leg. The proposed control strategy consists of three loops: open-loop simple boost control, output voltage control, and 2ω-ripple suppression control. Open-loop simple boost control is utilized for shoot-through state modulation, output voltage control is applied to the two bridge-legs of the H-Bridge, and the additional third bridge-leg adopts a quasi-PR control (QPR) method that injects specific frequency harmonic voltage and suppresses newly generated low-frequency components of the input current. This method effectively avoids the drawbacks of utilizing passive filtering strategies, such as high-value impedance networks, low power density, and weak system stability. A simulation platform of 300W 144VDC/110VAC50Hz is constructed. The simulation results indicate that the addition of the third bridge leg under full load conditions reduces the input-side inductor current ripple ΔI from 1.89 A with passive filtering to 0.513 A, representing a reduction of 72.86%. The second harmonic ripple of the input current is reduced from 18.2% to 4.5%, and the fourth harmonic ripple is reduced from 16.5% to 2.1%. The DC bus voltage ripple ΔVPN falls from 70.75 V to 6.54 V, representing a reduction of 90.76%. The Total Harmonic Distortion (THD) of the output voltage and current are both less than 1%. The simulation results validated the feasibility of the proposed approach.

実験値とデータシート値と近似式から構築した電力変換器の損失モデルの実機検証

This paper proposes a losses-analysis model of a DC-output converter based on the approximated equations from measurements and a datasheet. Target verification circuit consists of a DC-voltage source, a smooth capacitor, two half bridge legs, and a load inductor connected to the midpoints of the half bridge legs, which controls the continuous average DC current of the load inductor. A use of self-measured data, compared with the use of datasheet values, enables expanding the ranges of the considerable target parameters. Hence, lesser order approximated equations can deal with more target parameters with less calculation period than that in a conventional time domain simulation. In this study, calculation flow of losses from losses of power devices and an inductor to circuit losses was developed. Subsequently, a semiconductor losses model and inductor losses model were developed via the linear least square method. Finally, a 400V experimental system was developed to verify the accuracy of the circuit losses at 16 specified operating conditions by varying three verification parameters, switching frequency, gate resistance, and inductance. The result shows that the losses calculated using the proposed model has good accuracy with an error of 1.9% to 10.6% to the measured result.

Single-Phase Single-Stage Bidirectional DAB AC–DC Converter With Extended ZVS Range and High Efficiency

Conventional analyzations on the dual active bridge-based single-phase single-stage ac–dc converter relies on the line-piecewise model with which power switches are viewed as ideal and the commutation process between the top and bottom switch in each bridge leg are ignored. Although many soft-switching have been proposed, the effects of the commutation process make them inaccurate because of the difference between the line-piecewise model-based theoretical waveforms and the real ones. In this article, the commutation process is described in view of the nonlinearity of the switch junction capacitance, the commutation delay time and the dead time of each bridge leg. Furthermore, the control variables are compensated with the commutation delay time so that the zero voltage switching (ZVS) range can be extended widely. The variable dead time control helps to achieve critical turn-on, reducing the body diode conduction loss. Finally, a 1-kW prototype is built to evaluate the proposed method can achieve extend ZVS and achieve high conversion efficiency.

A Novel Junction Temperature Balance Control Method for Typical Three-Phase Converters Based on a Hybrid Modulation Strategy

Unbalanced junction temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> ) distribution of a bridge leg can accelerate the development of aging defects and reduce the lifetime of the converter. Therefore, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> balance control (TBC) is important for high reliability operation. Conventional TBC methods based on parameter adjustment cannot avoid reducing the efficiency and the power quality of converters. Other TBC methods can only be used in some switching devices in special packages. In this article, a novel TBC method is proposed based on a hybrid modulation strategy. First, temperature distributions in three space vector pulse width modulation (SVM) methods are analyzed theoretically and verified by experiments. This is the basis for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> balancing. Second, a hybrid modulation strategy is proposed based on the bang-bang control. It can switch from these three SVMs adaptively according to the maximum <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference. In this way, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference of a bridge leg can be controlled to a fixed range. Third, the effectiveness of the proposed TBC method is verified by experiments. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_j</i> difference caused by unbalanced aging can be controlled from over 20 °C to 3 °C. Compared with conventional TBC methods, the proposed method has almost no effect on the efficiency and output power quality of the converter.

Analysis of DC-Side Snubbers for SiC Devices Application

Due to parasitic parameters existing in Silicon Carbide (SiC) devices application, SiC devices have poor turn-off performances. SiC diode and SiC MOSFET have severe turn-off overvoltage and oscillation. The DC-side snubber is one simple suppressing method. The simplest circuit is the high-frequency decoupling capacitor in parallel with the bridge leg. However, choosing the component value is empirical. Based on the turn-off terminal impedances of the SiC diode and the SiC MOSFET, the suppressing mechanism of this DC-side snubber is analyzed. The guideline selection for the component value is provided. Furthermore, the DC-side snubber with a damping resistor is analyzed based on the terminal impedances. The design principles are provided. Finally, the validity and effectiveness of the DC-side snubbers were proven based on the double-pulse test platform.

LLC Resonant Converter Modulations for Reduced Junction Temperatures in Half-Bridge Mode and Transformer Flux in the On-the-Fly Morphing Thereto

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converters are typically unsuitable to be applied for wide voltage-transfer ratio applications. With a full-bridge inverter, however, they can be operated in a variety of different modulation modes to extend the operating range. Most notably, by permanently turning <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> one switch and turning <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> the other switch of the same bridge leg, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> can be operated in half-bridge mode reducing the gain by a factor of two. In this modulation, however, the switch that is permanently turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> is stressed by the complete resonant current while exhibiting no switching losses. This article proves that the frequency-doubler modulation can better balance the losses among all switches and should be the preferred mode of operation favored over the conventional half-bridge modulation. This article analyzes the beneficial loss distribution and proposes an on-the-fly morphing modulation to the frequency-doubler modulation and reverse. Furthermore, the morphing magnetizing current offset of the morphing is analyzed to show that the offset can be influenced by the design of the magnetizing inductance and through the morphing modulation itself. Finally, an improved morphing modulation is presented showing that the morphing flux offset can be reduced substantially. Experimental measurement results on a 1.8 kW prototype show that by employing the frequency-doubler modulation, the maximum inverter temperature can be reduced by about 20 K and that the maximum transformer flux deviation during morphing can be reduced significantly on average by 78%. Both results enable the use of switches with a lower on-state resistance and the application of transformers with a smaller core cross-section.

Fault-Tolerant Reconfiguration Topology and Control Strategy for Symmetric Open-Winding Multiphase Machines

This paper introduces a fault-tolerant reconfiguration topology and control strategy for symmetric open-winding multiphase machines. Bidirectional switching devices are proposed to connect the inverter bridge legs on different ends when the open-circuit fault occurs, and the reconfigured circuit can regenerate the missing voltage phasors due to the faults. Furthermore, to prevent overcurrent problems on the reconfigured bridge legs and maximize the torque output capability of the reconstructed system, winding currents are optimized with zero-sequence component injection during fault-tolerant operation. The experiments implemented on the five-phase system validate that the proposed fault-tolerant scheme is effective and has higher torque output capability compared with the traditional fault-tolerant solutions.

Improved PWM Methods to Reduce the Common Mode Voltage of the Five-Phase Open-Winding Drive Topology

With the phase angle and shape modifications for carriers, two improved carrier-based pulse width modulation (CPWM) methods with common-mode voltage (CMV) suppression effects for the five-phase open-winding drive topologies are introduced. Theoretical analysis reveals that, by employing reversed triangular carriers for two inverters under the carrier-reversed PWM (CRPWM), CMV contributions of two bridge legs belonging to the same phase can be cancelled, realizing the zero CMV effect. By dynamically employing positive and negative sawtooth carriers for all bridge legs under the carrier-switching PWM (CSPWM), the CMV contribution of each inverter can be reduced, decreasing both the amplitude and step frequency of the CMV. Current qualities and dead-time effects on CMV under the above PWM methods are analyzed. Moreover, performances of two PWM methods are verified by experiments implemented on a five-phase open-winding topology with the induction motor load.

A High-Efficiency and High-Power-Density Interleaved Integrated Buck-Boost-LLC Converter and Its Comprehensive Optimal Design Method

Integrated buck-boost- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> (IBBL) dcconverter is a good solution for high efficiency and high power density applications. However, the bridge leg integration causes asymmetrical zero-voltage-switching process and asymmetrical secondary current. The method of high quality factor or symmetric phase shift modulation proposed in the existing research can improve the asymmetrical current issue under heavy load, but is ineffective for light load conditions. This article proposes a novel Interleaved IBBL converter to improve the asymmetry issue for whole load range. Interleaving makes the secondary current be symmetric naturally. In addition, a comprehensive optimal design method for phase-shift angle and choke inductor is proposed to minimize the total power loss of all primary elements. A 600 W/1 MHz prototype verifies that the proposed IIBBL converter achieves symmetric secondary current in whole load range, and it achieves 95.7% efficiency and 180 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> under the proposed comprehensive optimal design method.

Fault-tolerant control via four-leg inverter of a full-electric propulsion system for lightweight fixed-wing UAVs

The work deals with the development and the performance characterization of a novel control strategy for the detection, isolation and accommodation of coil faults in a three-phase Permanent Magnet Synchronous Motor (PMSM), used to drive the propeller of a modern lightweight fixed-wing UAV. The health-monitoring algorithms on motor currents (used to detect the open-circuit fault and to activate the control reconfiguration) are based on a slope method, associated to the evaluation of the current phasor trajectory in the Clarke plane. Actually, when an open-circuit fault occurs in PMSM driven by a standard three-leg converter, the typical circular trajectory of the current phasor in the Clarke plane collapses into a linear track and relevant torque ripples are generated. On the other hand, if the PMSM is driven by a four-leg converter, a control reconfiguration can be applied: the fourth leg of the power bridge is in stand-by when the system operates without faults, but it is enabled to regulate the current flowing at the central point of the Y connection of the 3-phase PMSM. The performances of the fault-tolerant algorithms are assessed via detailed nonlinear simulation of the propulsion system (including propeller loads, electrical faults, mechanical transmission compliance, digital signal processing and sensors errors). The results demonstrate that the health-monitoring algorithms and the fault-tolerant control strategies permit to obtain extremely small detection and isolation latencies, and negligible performance degradation in terms PMSM torque.

Complete decoupling compensation of three‐phase inverter with LCL filter in synchronous reference frame

A decoupling control strategy of three-phase inverter, which can realize complete decoupling of the active and reactive current in the synchronous reference frame (SRF) is proposed here. There are two coupling factors of current loop in SRF, one is time delay caused by digital control, and the other is AC filter. Dynamic time delay compensation is applied to eliminate coupling caused by the first factor. The phase of the bridge leg voltage can be predicted. The difference between it and the phase of reference voltage which takes part in pulse width modulation (PWM) is the dynamic compensation angle, which can compensate the time delay. High-order feedforward compensation is applied to eliminate coupling caused by the second factor. Complex vector model of the LCL filter is derived and the high-order coupling coefficients can be offset by feedforward compensation. The coupling characteristics and compensation principles are analysed in detail. The system stability is discussed. Finally, the simulation and experimental results are given to verify the theoretical analysis.

Enabling Resonant Commutated Pole in Parallel Power FET Bridge Legs

To meet the requirements of higher current ratings and lower thermal impedances, paralleling power field-effect transistor (FET) discretes or modules is often a cost-effective or even an unavoidable solution. While paralleling FETs allows for a significant reduction in conduction loss, the switching loss is increased in hard-switching applications. This article proposes a generic soft-switching modulation scheme for parallel power FET bridge legs. Part of the paralleled FET legs is chosen as an auxiliary leg that is turned on prior to the remaining main legs. A resonant commutated pole (RCP) mode is then created, which enables the high-side FET of the auxiliary leg to achieve zero-current switching (ZCS) or quasi-ZCS and the remaining FETs to achieve zero-voltage switching. Thus, we can significantly reduce the switching loss that normally dominates the total power loss of high-frequency hard-switching converters particularly at partial and light loads. Experimental results from three parallel GaN high-electron-mobility transistor legs validate the effectiveness of this RCP-enabled solution in reducing switching losses and improving power conversion efficiencies. This article is accompanied by supplementary JIF and PDF files demonstrating the operational details of the RCP mode.

An Effective Integration of APM and OBC With Simultaneous Operation and Entire ZVS Range for Electric Vehicle

This article proposes an effective integration of APM and OBC providing simultaneous operation without an extra circuit and entire ZVS range of all switches. The integrated circuit of the proposed charger is configured by combining high voltage-side switch legs of the LLC resonant converter of OBC and the PSFB converter of APM. In the simultaneous mode, by operating the common leg as a lagging leg of the phase-shift full bridge (PSFB) converter, the conduction losses of the common leg switches are decreased due to current cancellation effect, and the lagging leg switches of the PSFB converter achieve entire ZVS operation. Further, in the APM standalone mode, entire ZVS operation of the lagging leg switches is also secured by utilizing the magnetizing current of the LLC resonant converter. As a result, the proposed integrated charger achieves comprehensive improvement in terms of efficiency as well as volume and cost. A laboratory prototype combining a 3.7-kW LLC resonant converter with a 1-kW PSFB converter is built and tested in order to verify the performance and theoretical claims.

Hybrid SVPWM Modulation Strategy for Auxiliary Resonant Commutated Pole Inverter

Although the auxiliary resonant commutated pole inverter (ARCPI) can achieve soft-switching for main switches, the auxiliary commutation circuit (ACC) itself has a loss, especially under high frequency. To reduce the loss of ACC and optimize the efficiency of the ARCPI, this article proposes a hybrid space vector pulsewidth modulation (SVPWM) strategy. It can not only compensate for the influence of dead time but also reduce the operation times of the ACCs. First, the operation principles of an ARCPI are briefly analyzed. The topology can achieve soft-switching reliably for all switches with simplified ACCs. Then, appropriate zero vectors are designed for the hybrid SVPWM modulation strategy, which can guarantee that unnecessary switching actions are eliminated, and the switches in each bridge leg conduct symmetrically. Furthermore, the trigger pulse generation method for ACCs based on only one main switch is designed. Finally, the simulation and experimental results are given to demonstrate the validity of the proposed strategy.

Neutral Point Clamped Transformer-Less Multilevel Converter for Grid-Connected Photovoltaic System

Transformer-less (TL) inverter topologies have elicited further special treatment in photo-voltaic (PV) power system as they provide high efficiency and low cost. Neutral point clamped (NPC) multilevel-inverter (MLI) topologies-based transformer-less are being immensely used in grid-connected medium-voltage high-power claims. Unfortunately, these topologies such as NPC-MLI, full-bridge inverter with DC bypass (FB-DCBP) suffer from the shoot-through problem on the bridge legs, which affect the reliability of the implementation. Based on the previous above credits, a T type neutral point clamped (TNP)—MLI (TNP-MLI) with transformer-less topology called TL-TNP-MLI is presented to be an alternate which can be suitable in the grid-connected PV power generation systems. The suggested TL-TNP-MLI topologies free from inverter bridge legs shoot-through burden, switching frequency common-mode current (CMC), and leakage current. The control system of the grid interface with hysteresis current control (HCC) strategy is proposed. The effectiveness of the proposed PV connected transformer-less TNP-MLI topology with different grid and PV scenario has been verified through the MATLAB/Simulink simulation model and field-programmable gate area (FPGA)-based experimental results for a 1.5 kW system.

Comparative Analysis of the Electromyography Activity of Core Muscles During Balance Pad- and Sling-assisted Exercises

Background: Unstable surface-based core training can significantly enhance core strength, but no studies have compared the effects of balance pad- and sling-assisted exercises. Objects: To study the effects of unstable surface-based balance pad- and sling-assisted core strength exercises on muscle activity. Methods: Twenty male students aged 20-25 years participated in this study. The effects of three types of core strength exercises, performed with a sling or balance pad, on the activities of three muscles, i.e., the right musculus obliquus externus abdominis (EO), right erector spinae (ES), and right gluteus maximus (GM), were examined. Results: 1) In the glute bridge exercise, the percentage of maximum voluntary contraction of the EO, ES, and GM were significantly different between the balance pad- and sling-assisted exercises. The relative contribution of the ES and GM activities to all muscle activity were not significantly different between the two training types, whereas that for EO showed a significant difference. 2) There was no significant difference in the percentage value of maximum voluntary contraction (%MVC) among the EO, ES, and GM during the “leg-lifting with flat support”exercise, and there were no significant difference in the relative contributions between the two training types. 3) In the “side bridge leg separation exercise”, the %MVC of the ES, EO, and GM were significantly different between the two training types. Conclusion: Sling training for core muscles was generally better than balance pad assist training. The majority of physiotherapy patients require core training. Our results could guide physiotherapists in the choice of targeted exercises for these patients.