Switching Power Losses Research Articles

(Invited) Beta-Gallium Oxide-Based Devices Towards Grid-Scale Electronics

Gallium Oxide is an emerging ultra-wide band gap semiconductor with promising material properties relevant for high performance power electronic devices. The availability of large area bulk substrates using melt growth techniquesand the wide range of tunable n-type conductivity makes it a compelling semiconductor material platform for next-generation power devices. Lateral Devices: Homoepitaxial Si-doped channel layers are grown using metal-organic vapor phase epitaxy (MOVPE) on NCT and Synoptics (010) Ga2O3 bulk substrates after chemical cleaning to minimize impurities at the substrate-epitaxial layer interface, necessary for pinching off the lateral field effect transistors. Excellent electron mobilities, contact resistance values, breakdown voltages and power figures of merit are demonstrated in β-Ga2O3 epitaxial films and devices. MOVPE-grown β-Ga2O3 thin films with electron mobility values close to the predicted theoretical maximum (~ 200 cm2/Vs) are achieved at low (600°C) and high (800°C) growth temperatures. A low-temperature MOVPE masked ohmic contact regrowth technique is developed with a low contact resistance value. Multi-kilovolt (up to 4.5 kV) class β-Ga2O3 transistors are demonstrated with state-of-the-art power figures of merit exceeding several times the theoretical maximum of Silicon. A channel-buffer stack engineering is demonstrated that enabled record-high electron mobility values in doped β-Ga2O3 films. High-current (> 100 mA/mm) and VBR (up to ~ 3kV) β-Ga2O3 MOSFETs are realized on an engineered β-Ga2O3 /SiC composite substrate – for enhanced bottom-side device cooling. Tri-Gate β-Ga2O3 MESFETs with record high power figure of merit (~1 GW/cm2) are demonstrated. We report on the demonstration of kV-class β-Ga2O3 MOSFETs fabricated on 1-in. bulk substrates using metalorganic vapor phase epitaxy (MOVPE) with disilane (Si2H6) as the silicon precursor. In this talk, we will highlight some of these critical advances in β-Ga2O3 epitaxy/devices, pushing the boundary of β-Ga2O3device performance. Vertical Devices: Gallium Oxide devices are very attractive for next-generation grid-scale power rectifiers and transistors. We report a vertical β-Ga2O3 Schottky barrier diode (SBD) with BaTiO3 as field plate oxide on a low doped thick epitaxial layer exhibiting 2.1 kV breakdown voltage. A thick drift layer of 11 μm with a low effective doping concentration of 8 × 1015 cm–3 is used to achieve high breakdown voltage. Using the high-k dielectric with a dielectric constant of 248, the breakdown voltage increases from 816 V for the non-field-plated SBD to 2.1 kV (>2× improvement) for the field-plated SBD without compromising the on-state performance.We introduce vertical Schottky barrier diodes (SBDs) based on β-Ga2O3 with trench architecture, featuring a high-permittivity dielectric RESURF structure. These diodes are designed for application demanding high voltage and current capacities while maintaining ultra-low reverse leakage currents. The trench design plays a pivotal role in reducing the electric field at the metal–semiconductor junction, thereby yielding minimal reverse leakage attributed to field emission under high reverse bias conditions. Additionally, the incorporation of a high-k dielectric helps to suppress leakage through the trench bottom corner dielectric layer. The incorporation of a trench geometry, coupled with the high-permittivity dielectric RESURF, effectively reduces the surface electric field at the metal-semiconductor junction. This reduction facilitates the use of a lower work-function anode contact, further diminishing the turn-on voltage. The use of high-k dielectric also significantly reduces the dielectric leakage contribution to the overall reverse leakage of the diode. Large-area SBDs with areas of 1mm2 and 4mm2 exhibit pulsed forward current of 6A/20A and a catastrophic breakdown voltage of 1.74kV/1.4kV, surpassing other β-Ga2O3-based large-area power diodes, while small-area SBDs (200×200 µm2) do not exhibit catastrophic breakdown until 3kV. The large-area SBDs also demonstrate lower capacitance, stored charge, and stored energy compared to commercial SiC SBDs, indicating potential for superior switching performance. The combination of lower stored charge and a low forward voltage drop results in an excellent trade-off between conduction and switching power loss, yielding a QCVF figure of merit comparable to commercial bare die SiC SBDs.We report on the fabrication and characterization of a NiOx/β-Ga2O3 heterojunction diode (HJD) that uses a metallic Nickel (Ni) target to deposit NiOx layers via reactive RF magnetron sputtering and lift-off processing with >3 kV breakdown voltage, record-low reverse current leakage under high reverse bias, and high junction electric fields (4 MV/cm). The breakdown voltage was measured to be greater than 3 kV with a noise floor-level reverse leakage current density (~10-6 A/cm2) until 3 kV. Such rapid advances in Gallium Oxide device engineering will unleash the potential for these devices for next-generation grid-scale power electronics. We acknowledge funding from the Coherent/II–VI Foundation and AFOSR.

Performance Evaluation of the Two-Input Buck Converter as a Visible Light Communication High-Brightness LED Driver Based on Split Power.

This work proposes a high-efficiency High-Brightness LED (HB-LED) driver for Visible Light Communication (VLC) based on a Two-Input Buck (TIBuck) DC/DC converter. This solution not only outperforms previous approaches based on Buck DC/DC converters, but also simplifies previous proposals for VLC drivers that use the split power technique with two DC/DC converters: one is in charge of the communication tasks and the other controls the biasing of the HB-LED (i.e., lighting tasks). The real implementation of this scheme requires either two input voltage sources, one of which is isolated, or one DC/DC converter with galvanic isolation. The proposed implementation of splitting the power is based on a TIBuck DC/DC converter that avoids the isolation requirement, overcoming the major drawback of this technique, keeping high-efficiency and high communication capability thanks to the lower voltage stress both across the switches and at the switching node. This fact allows for the operation at very high frequency for communication purposes, minimizing switching power losses, achieving high efficiency and providing lower filtering effort. Moreover, the duty ratio range can also be adapted to the useful voltage range of the HB-LED load to maximize the resolution on the tracking of the output volage. The power is split by means of an auxiliary Buck DC/DC converter operating at low switching frequency, which generates the secondary voltage source needed by the TIBuck DC/DC converter. This defines a natural split of power by only processing the power delivered for communications purposes at high frequency. A 7 W output-power experimental prototype of the proposed VLC driver was built and tested. Based on the experimental results, the prototype achieved 94% efficiency, reproducing a 64-QAM digital modulation scheme and achieving a bit rate of 1.5 Mbps with error in communication of 12%.

A Flyback Converter with a Simple Passive Circuit for Improving Power Efficiency

This paper proposes an effective method to improve the power efficiency of the flyback converter in the continuous conduction mode (CCM). The proposed converter uses a simple passive circuit to reduce the switching power losses. The current through the output diode can be shifted to a new branch where one diode, one inductor, and one auxiliary winding of the transformer are included. The output diode current can be reduced to zero for the zero-current switching of the output diode. The additional inductor is used to control the changing rate of the additional diode current to reduce the reverse-recovery current. Keeping the simplicity of the passive method, the proposed converter improves the power efficiency compared to the conventional converter. The circuit configuration and the operation principle are described. The design considerations are presented, including the simulation verification. The experimental results for a 45 W prototype are discussed to evaluate the performance of the proposed converter. The proposed converter has achieved a power efficiency of 93.5% for the rated load condition, improving the power efficiency. The applications of the proposed converter are also discussed for the future research directions.

High-k Dielectrics-Based Electric Field Engineering in β-Ga2O3 Power Diodes

We present β-Ga2O3 high-voltage Schottky barrier diodes (SBD) incorporating advanced electric field engineering approaches through the use of high-permittivity dielectrics. We present two approaches: 1) the lateral dielectric superjunction SBD, where the electric field within the drift layer is modified from triangular to rectangular profile, enhancing the breakdown voltage and enabling the use of higher drift layer doping to reduce on-resistance, and 2) the vertical high-k RESURF trench SBD, which leverages the reduced surface electric field effect (RESURF) to reduce the electric field at the metal-semiconductor junction and reverse leakage currents.A superjunction-like structure uses charge balance to push the VBR-Ron-sp trade-off beyond the material’s unipolar figure of merit. The lack of p-type doping in β-Ga2O3 makes the realization of such structures very difficult. However, field flattening can be achieved in β-Ga2O3 drift layers using a high permittivity material with appropriate choice of dielectric constant, device aspect ratio and semiconductor/dielectric width. An analytical model is discussed to highlight the device design strategy and experimental demonstration is reported in the lateral geometry. 500 nm of Si-doped Ga2O3 epitaxial layer with a sheet charge of 1.6×1013 cm-2 is grown using metal organic vapor phase epitaxy (MOVPE). Trenches with three different fin widths (WFin = 2, 5, 10 µm) were made and high-k dielectric BaTiO3 (BTO) with dielectric constant of 220 is deposited on the sample. A low specific on resistance of 1.65 mΩ-cm2 is observed for LAC = 5µm due to the high charge density epitaxial lateral Fins. For the SBD with LAC = 5µm and WFin = 5µm, a high average electric field of ~3 MV/cm (VBR/ LAC) is estimated across the entire length of the device. A very high Baliga's figure of merit (BFOM) of 1.35 GW/cm2 is observed for the RESURF SBD with LAC=5µm and WFin=2µm (VBR=1.49 kV and Ron-sp=1.65 mΩ-cm2), surpassing SiC unipolar FOM when considering just the conducting area.While superjunction-like structures effectively flatten the electric field inside the drift layer, high electric fields at the metal/semiconductor junction results in increased leakage current at large reverse bias, particularly in the case of vertical Schottky Barrier Diodes (SBDs). To circumvent this challenge, we present the approach of β-Ga2O3 Vertical Trench Schottky Barrier Diode (SBD) with a high-permittivity dielectric RESURF. The incorporation of a trench geometry, coupled with the high-permittivity dielectric RESURF, effectively reduces the surface electric field at the metal-semiconductor junction. This reduction facilitates the use of a lower work-function anode contact, further diminishing the turn-on voltage. The use of high-k dielectric also significantly reduces the dielectric leakage contribution to the overall reverse leakage of the diode. Large-area SBDs with areas of 1mm2 and 4mm2 exhibit pulsed forward current of 6A/20A and a catastrophic breakdown voltage of 1.74kV/1.4kV, surpassing other β-Ga2O3-based large-area power diodes, while small-area SBDs (200×200 µm2) do not exhibit catastrophic breakdown until 3kV. The large-area SBDs also demonstrate lower capacitance, stored charge, and stored energy compared to commercial SiC SBDs, indicating potential for superior switching performance. The combination of lower stored charge and a low forward voltage drop results in an excellent trade-off between conduction and switching power loss, yielding a QCVF figure of merit comparable to commercial bare die SiC SBDs. We demonstrate the potential of high permittivity dielectrics-based extreme field engineering to push the performance limits of β-Ga2O3 diodes for next-generation power electronics.We acknowledge funding from AFOSR MURI program (Dr. Ali Sayir) and Coherent/II-VI foundation.

An improved voltage gain bidirectional DC/DC converter based on voltage multiplier cell for electric vehicle application

ABSTRACT The global energy crisis has raised environmental concerns, leading governments to invest in renewable energy and address electric vehicle (EV) and hybrid EV (HEV) difficulties. One of the main challenges is the interface between the energy storage system and the DC-link of the three-phase inverter. For this aim, an improved voltage gain bidirectional DC/DC converter based on a voltage multiplier cell (VMC) is proposed in this paper, which acts like a high boost converter when the energy storage system is powering the EV and a buck converter when regenerative braking is required. The proposed bidirectional converter has advantages like low device account, simple structure, reduced switching power losses, high voltage gain, common ground, and increased efficiency. An output voltage of 10 times the input voltage in boost mode is provided by the proposed converter. Also, the proposed converter can generate a voltage 0.26 times lower than the input voltage in buck mode. The operating principle and comparative analysis with other existing converters are presented. Moreover, the efficiency calculation is discussed by assuming the non-ideal parameters. The proposed converter has a maximum efficiency of 97.78%. Finally, a 500 W simulation prototype is implemented in PSIM software to confirm the theoretical analysis.

Optimal design of PV-SMES systems for power quality enhancement using pelicon optimized multi-level inverter model

In this article, a superconducting magnetic energy storage (SMES) system is integrated with a photovoltaic (PV) renewable energy source. The integrated system can achieve power balancing with voltage stability, high power quality, and reliability. Here, a Bonobo Optimization Algorithm (BOA)-based MPPT control has been developed to get the most electrical energy out of the solar PV cells under fluctuating weather conditions, including temperature and irradiance. The output voltage is greatly increased with minimal switching complexity by using the Zeta DC-DC converter, which helps to meet the energy requirements of load applications. Then, the Total Harmonics Distortions (THD) has been decreased with lower switching stress, power loss, and voltage ripples at the load using the sophisticated and simple five-level MLI circuit model. In addition, the performance of MLI has been greatly improved by tuning the controlling gain parameters with the use of Pelicon Optimization (PO) technique. Moreover, the Shunt Active Power Filter (SAPF) is used in order to achieve the best power quality results with the reduced overall harmonic distortions. The performance and results of the suggested circuit model are validated in this study through a complete simulation analysis using a variety of assessment indicators.

Research on controlling dual buck inverter in sliding mode based on buffered inductor

Abstract To overcome the problems of power transistor passthrough and switching loss in traditional bridge inverters, it is suggested to replace the conventional double Buck inverter with a double Buck inverter that has a buffer inductor placed in the center of the bridge arm with one that has a very modest inductance value. Firstly, a dual inductor single structure of the Buck inverter was examined, and based on this, a dual Buck inverter topology structure based on a buffer inductor was proposed. Then, the application of the sliding mode control strategy in dual Buck inverters based on buffer inductance was elaborated. Ultimately, tests were conducted to confirm the accuracy of the theoretical theory. The proposed dual Buck inverter based on buffer inductance solves the problem of low inductance utilization while retaining high reliability. Compared with single inductance DBI, it has smaller losses and lower control complexity, which has practical application value.

Extended high gain DC‐DC converter with switched‐inductors, switched‐capacitors and soft‐switching: Analysis and implementation

AbstractThis paper proposes an extended DC‐DC converter with high voltage conversion ratio and soft‐switching ability. The proposed converter has active switched‐inductors, switched‐capacitors included in the conventional high gain converter and operates in continuous conduction mode (CCM). Simple auxiliary resonant elements are added on the primary leg of the converter to provide design freedom for soft‐switching operation. The significant merits of the proposed converter are lesser voltage and current stresses, high voltage gain with reduced component count and better efficiency. Additional feature of this converter is soft‐switching operation under different load conditions and duty ratios without considerably increasing stresses. The zero voltage switching (ZVS) turn‐on operation is obtained for all switching devices. Therefore, switching power losses are minimized greatly. This paper presents the description, principles of operation and steady state analysis in comparison with the existing high gain converters. The theoretical analysis is verified with a 350 W prototype operated at input is 20 V and output is 220 V. The overall efficiency achieved is 96.7%. The obtained results confirm ZVZCS operation at full load.

A high step‐up high step‐down coupled inductor based bidirectional DC–DC converter with low voltage stress on switches

AbstractThis paper proposes, a novel soft‐switching bidirectional direct current to direct current (DC–DC) converter based on switched‐capacitor and coupled‐inductor. The proposed converter has a simple structure and utilizes four switches and a three‐winding coupled inductor and can achieve a high voltage conversion ratio in both step‐up/step‐down operations. By employing the switched‐capacitor technique, voltage stress across the power switches is low and therefore low voltage rating switches can be adopted to reduce the losses of their conduction. Soft‐switching characteristic of the proposed converter reduces the switching loss of active power switches and raises the conversion efficiency. This paper presents theoretical analysis for all operating modes of the converter, voltage conversion ratio, voltage and current stresses of all power switches. Finally, to test the validity of theoretical results and demonstrate the performance of the converter, experimental results are provided.

An inimitable Elman network based fire hawk controller and skill optimized power tracker with ultra gain converter for improving the performance of PV tied EV systems

The need for Electric Vehicles (EVs) has grown as a result of the issues brought on by fossil fuels. To keep up with the rising demand for electricity, the power source is equipped with additional renewable energy sources (RES). In order to meet the demand for energy, the solar photovoltaic (PV) system is deployed in this work. The novel contribution of this paper is the design and development of unique converter and regulating models to improve the overall power tracking performance, voltage gain, power quality, motor performance and efficiency of the PV-EV system. Here, a cutting-edge MPPT controlling model known as, Skill Optimized Power Tracker (SOPT) is developed in this work to maximize the quantity of electrical energy generated by solar panels in the context of changing temperature and irradiance. This work effectively increases PV output by adopting an innovative Ultra high gain converter, which increases voltage gain efficiency with less switching stress and power loss. In particular, this endeavor develops a unique Inimitable Elman Network based Fire Hawk Controller (IEFC) to improve the power quality and motor performance of EVs. Moreover, the simulation results of the proposed SOPT-IEFC controlling model and Ultra-high gain converter are validated through an array of performance measures including overall efficiency (99%), THD (1.05%), and motor speed (1200 rpm).

A Novel Mixture-Devices-Based Submodule for MMC by Using Low on-State Voltage IGCT and High di/dt Ability IGBT

At present, insulated-gate bipolar transistor (IGBT) is widely used as the converter component in the submodule of modular multilevel converter (MMC) for its excellent performance in driving circuit and switching speed, but the further application is restricted by its high conduction loss and cost rate. Integrated gate-commutated thyristor (IGCT) is another converter device used in MMC with low conduction loss and cost. However, the d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> capability of IGCT is limited so that a snubber circuit is required in the submodule for protection, which generates unwanted power loss for MMC. For better performance and reliability, this paper proposes a mixture-devices-based submodule (MS) for MMC based on the cooperation of parallel IGCT and IGBT devices. Double-pulse switching experiments for the MS are conducted to verify its effectiveness, and to get the data for the follow-up switching power loss calculation. The power loss of MMC based on IGBT, IGCT and mixture devices are calculated based on the model established in this paper. Furthermore, the comprehensive comparison for power loss among IGBT-based, IGCT-based and mixture-device-based MMCs are performed, proving the effectiveness of the mixture topology in terms of power loss reduction. Meanwhile, the proposed MS is cost-competitive.

A partial soft-switching SiC-based ANPC single-phase inverter with loss model-based dead time optimization for grid-tied PV systems

Single-phase string inverter has been widely applied to grid-tied photovoltaic (PV) rooftop applications for its renewable energy. However, the inherent attribute of intermittency in solar energy may induce instability and unqualified power. To meet the grid-interconnection standards, high demands of efficiency and harmonic distortion need to be imposed on DC/AC inverters. Conventional soft-switching inverters used to sacrificing auxiliary resonant circuits to exchange for soft switching. This requires additional costs as well as sufficient dead time to discharge junction capacitances of all switches, which exacerbates total harmonics distortion (THD) induced by dead-time effect. To improve, this paper proposes a partial soft-switching silicon carbide (SiC) -based active neutral-point-clamped (ANPC) inverter, which possesses high efficiency, eligible dead time, and no auxiliaries. 650-V SiC MOSFET is adopted for its smaller output capacitance compared with Si device. Hybrid PWM modulation is utilized to achieve partial soft switching. Whereas, the soft switching realization range and power losses highly depend on the dead time. To achieve less power loss and improved dead time effect, this paper proposes a loss model-based dead time algorithm through a Power Loss VS. Dead Time mathematical loss model. Moreover, the mechanism of the dead time affected by soft switching is explored. The transition modes, dead time configurable boundaries, and design procedure are also analyzed in detail. A 1-kW prototype is demonstrated with the input of 800 V and the rated output of 220 V/ 4.5 A. Its efficiency could reach 99.6% with THD=0.95% at full power level.

Алгоритм трехфазной широтно-импульсной модуляции при ограничении на потери мощности в электронных ключах в системе преобразователь–электродвигатель

The process of pulse width modulation (PWM) in a converter–electric motor system is considered. It is shown that for the synthesis of converter control systems, along with сontinuous PWMs (CPWM), discontinuous PWMs (DPWM) are also used, the advantage of which is a relatively low number of switching of the key elements of the converter. The algorithm of three-phase PWM, optimal by the criterion of current dispersion in the load, is considered, taking into account the limitations on power loss in electronic switches. Expressions for the integral dispersion of the load current are obtained. For a comparative evaluation of the algorithms, a criterion is formulated in the form of efficiency coefficients for сontinuous PWM and discontinuous PWM methods. The tolerance range of the appropriate modulation with a minimum number of commutations in the space of the amplitude coefficient and the relative frequency of the nominal modulation is obtained. The dependences of the efficiency coefficient of the discontinuous PWM algorithm at an increased modulation frequency are obtained depending on the amplitude coefficient and the relative modulation have been established.

Full-Si-Based Two-Stage VSI and Its Specialized Modulation Strategy to Reduce Switching Power Loss and Increase PWM Harmonic Frequency

Full-Si-Based Two-Stage VSI and Its Specialized Modulation Strategy to Reduce Switching Power Loss and Increase PWM Harmonic Frequency

A Novel Hybrid PWM Technique for Asymmetric Inverter

Multi-Level Inverters (MLIs) are achieving broad popularity owing to the rapid development of power semiconductor devices. The capability of MLIs became recognized as a significant aspect of a system heavily reliant on Pulse Width Modulation(PWM) strategy. The conventional high frequency PWM techniques suffer from significant Total Harmonic Distortion (THD) along with power loss difficulties. This work recommends a hybrid PWM technique for lowering the THD and power loss of VSI adding the benefits of level-shift PWM and Phase-shift PWM. A novel form of carrier signals is employed in the proposed hybrid PWM technique. In contrast to existing PWM techniques, the proposed hybrid PWM technique minimizes switching and conduction power losses. In this work, the proposed PWM scheme is employed for asymmetric multilevel inverter. The proposed configuration is also examined using PLECS software to estimate losses and efficiency. The simulation work is done in the MATLAB/Simulink environment and the OPAL-RT(OP4510) test platform is employed to evaluate topology performance.

Technical Reviews of Power Loss Optimization in High-Frequency PSiPs—In Relation to Power Switches and Power Inductors

Power losses of switches and inductors are consistent challenges that hinder the development of high-frequency power supply in package (PSiP). This paper investigates the roadmap for power loss optimizations of switches and inductors in high-frequency PSiPs. Firstly, a size and parallel quantity design method to reduce power loss in an integrated Si LDMOSFET is provided with comprehensive consideration of switching frequency and power levels. Secondly, quality factors of different air-core inductors are analyzed with consideration of geometric parameters and skin effect, which provides the winding structure optimization to reduce power losses. The power losses of the integrated Si LDMOSFET and air-core inductors are both reduced to less than 10% of the output power at 1~100 MHz switching frequency and 0.1~10 W power level. Finally, based on the above optimizations, power losses of switches and inductors are calculated with switching frequency and power level. Combining the calculated results, this paper predicts the efficiency boundaries of PSiPs. Upon efficiency normalization with consideration of input and output voltage levels, all the predictions are consistent with the published literature. The efficiency predication error is 1~15% at 1~100 MHz switching frequency and 0.1~10 W power level. The above power loss optimizations improve the efficiency, which provides potential roadmaps for achieving high-frequency PSiPs.

Power losses in the MOSFET transistors of switching-mode converters

The power losses in the MOSFET transistors of switching-mode converters are investigated and analyzed. The results presented in this paper are achieved using software Cadence OrCAD. The simulation model suitable for estimation of energy dissipations in MOSFET transistors is proposed. The power losses as a function of different circuit’s parameters, like switching frequency, power supply voltage and output current are evaluated. The PSpice model of MOSFET transistor “BSC020N03MS” of the company Infineon is used in the presented analysis. Control circuit, which realize the adaptive deadtime (ADT) control technique depending on the load current, is applied to reduce the switching power losses in the MOSFET transistor. Thus, the efficiency of the switching-mode converters can be increased.

Model predictive control for multimode power-split hybrid electric vehicles: Parametric internal model with integrated mode switch and variable meshing losses

Model predictive control (MPC) is one of the most promising energy management strategies for hybrid electric vehicles. However, owing to constructive complexity, the multimode power-split powertrain requires dedicated mathematical tools to model the mode switch and transmission power losses within the internal model of the controller. Thus, the transmission losses are usually neglected and the mode switch is optimised through offline simulations. This paper proposes an MPC internal model relying on a parametric approach available in the literature, which provides a unique formulation for modelling any power-split transmission and assesses the transmission meshing losses. The objectives, which cover a gap in the literature, are: 1) to integrate the discrete problem of the mode switch in a continuous formulation of the internal model; 2) to compare MPC internal models with different complexity, and evaluate how the consideration of meshing losses and efficiency of the electric machines affect the controller performance. The results on a case study vehicle, i.e., the Chevrolet Volt, suggest that a simplified internal model deteriorates the fuel consumption performance by less than 2 %, while the integrated mode switch is comparable to the offline strategy.

Practical Dead-Time Control Methodology of a Three-Phase Dual Active Bridge Converter for a DC Grid System

An effective dead-time control strategy for the three-phase dual active bridge (3P-DAB) converter of a distribution system is studied to reduce the switching losses of power switches and improve the under-light-load power conversion efficiency. Because of the advantages of a dual-active bridge converter, such as an inherent zero-voltage switching (ZVS) capability without any additional resonant tank and a seamless bi-directional power transition, this is an attractive topology for bi-directional application. The 3P-DAB converter is apt for high-power applications such as aircraft due to an interleaved structure, which can reduce conduction losses. However, the design of the dead time depends on engineering experience and empirical methods. In order to overcome the conventional practicality of the dead-time design method, the effective control of dead time is proposed based on the theoretical analysis. In this paper, the overall explanation of the 3P-DAB converter is shown with operation principles. In addition, the dead-time effect of the 3P-DAB converter is examined and the practical variable dead-time control strategy is studied. Finally, experimental results validate the proposed variable dead-time control strategy using a 25 kW prototype 3P-DAB converter.

A novel multi-input medium-gain DC-DC boost converter with soft-switching performance

This paper proposes a new non-isolated dual-input zero-voltage switching (ZVS) dc-dc boost converter with medium voltage gain. Two input ports of the converter are current-fed and suitable for a unidirectional dc power source, and a chargeable dc energy storage. The proposed converter basic circuit composed of three cascaded power switches, which at their connection points join to the converter three inductors and a switched capacitor voltage multiplier (VM) cell is accompanied. Using this VM cell the converter voltage gain achieves two times of that in the conventional boost converter and also half voltage stress across the power switches. Through the converter two input inductors powers from a unidirectional source (like PV) and a chargeable battery source can be accepted. Taking a triangular resonant current at the switching frequency, the converter third inductor aids to reach ZVS for the power switches. The converter power switches turn-on with ZVS and the power diodes stop conducting with ZCS in all operation conditions. As a result, low switching power losses, reduced reverse recovery issue, and high efficiency are accessible especially for higher input and output powers. The converter power switches are switched in PWM manner with two individual duty ratios, allowing to regulate the output voltage and control the extracted power from the input unidirectional port. The proposed circuit has been analyzed in detail to find its different operating modes, determine its capacitor currents, estimate its power losses components and design its control system. Behavior of the proposed system is also examined by a low-power laboratory prototype tested under four different practical operation conditions. The proposed converter benefits from simple and compact structure, current-fed input ports, low number of power switches and magnetic elements, low voltage stress across the power switches, medium voltage gain and high efficiency.