High Power DC-DC Converter Research Articles

Review of dc–dc converters for multi‐terminal HVDC transmission networks

This study presents a comprehensive review of high-power dc-dc converters for high-voltage direct current (HVDC) transmission systems, with emphasis on the most promising topologies from established and emerging dc-dc converters. In addition, it highlights the key challenges of dc-dc converter scalability to HVDC applications, and narrows down the desired features for high-voltage dc-dc converters, considering both device and system perspectives. Attributes and limitations of each dc-dc converter considered in this study are explained in detail and supported by time-domain simulations. It is found that the front-to-front quasi-two-level operated modular multilevel converter, transition arm modular converter and controlled transition bridge converter offer the best solutions for high-voltage dc-dc converters that do not compromise galvanic isolation and prevention of dc fault propagation within the dc network. Apart from dc fault response, the MMC dc auto transformer and the transformerless hybrid cascaded two-level converter offer the most efficient solutions for tapping and dc voltage matching of multi-terminal HVDC networks.

Characterization of 6.5 kV IGBTs for High-Power Medium-Frequency Soft-Switched Applications

Medium voltage high-power applications are usually realized using high voltage semiconductors (3.3 kV and above) operated in the hard switching mode with low switching frequencies (several hundreds of hertz). However, for high-power dc-dc converters employing a transformer for galvanic isolation, it is attractive to increase the switching frequency so that the transformer size can be reduced. An increase of the switching frequency implies an increase of the switching losses, and this has to be mitigated somehow, usually by choice of resonant topologies or soft switching techniques. Main focus of the paper is on the operation of the insulated gate bipolar transistor (IGBT) within a high-power dc-dc LLC resonant converter, in order to explore interactions between semiconductor and circuit properties, which both must be simultaneously considered in order to achieve the best utilization of a high voltage power semiconductor operating at higher switching frequencies. For these purposes, switching properties of a standard 6.5 kV IGBT are compared with switching properties of two different optimized versions of a 6.5 kV IGBT. Experimental results are included to support theoretical considerations and findings.

Analysis on some Key Problems of High Power DCDC Converter for Fuel Cell Electrical Bus

The significance of researching on fuel cell electrical vehicle (FCEV) DC/DC converter, FCEV driving system structure and requirement with DC/DC converter are introduced firstly. Some key problems of development in FCEV DC/DC converter are particularly analyzed, including of reliability, efficiency, static and dynamic characteristic, etc. The average efficiency of boost or buck circuit can reach more than 95%. The dynamic response time of DC/DC converter is below 160 ms. All kinds of DC/DC converters operate with zero error, and various technical indicators can satisfy the operating requirement. The converters are successfully used in china fuel cell city buses and technical indexes are fulfilled.

Revised Magnetics Performance Factors and Experimental Comparison of High-Flux Materials for High-Current DC–DC Inductors

High-flux-density materials, such as iron-based amorphous metal and 6.5% silicon steel for gapped inductors, and powdered alloys for gapless inductors, are very competitive for high-power-density inductors. The high-flux-density materials lead to low weight/volume solutions for high-power dc-dc converters used in hybrid-electric and electric vehicles. In this paper, the analytical selection of the magnetic materials is investigated, and modified performance factors are introduced for convection- and conduction-cooled magnetic components. The practical effects of frequency, dc bias, flux-density derating, duty cycle, airgap fringing on the core loss, and thermal configuration based on lamination direction are investigated for iron-based amorphous metal, 6.5% silicon steel, and iron-based powdered alloy material. A 2.5-kW converter is built to verify the optimum material selection and thermal configuration. Analytical, simulation, and experimental results are presented.

Pwm control of dual active bridge: Comprehensive analysis and experimental verification

The dual-active-bridge (DAB) topology is ideally suited for high-power dc-dc conversion, especially when bidirectional power transfer is required. However, it has the drawback of high circulating currents and hard switching at light loads, if wide variation in input and output is expected. To address these issues, this paper presents a comprehensive analysis and experimental results with pulsewidth-modulation (PWM) control of the DAB. The PWM control is in addition to phase-shift modulation between the two H-bridges. The analysis addresses PWM of one bridge at a time and of both bridges simultaneously. In the latter, five distinct modes arise based on the choice of PWM and load condition. The possibilities are analyzed for optimizing power density and efficiency for low-load operation. Finally, a composite scheme combining single and dual PWM is proposed that extends the soft-switching range down to zero-load condition, reduces rms and peak currents, and results in significant size reduction of the transformer. Experimental results are presented with a 10-kW prototype.

인덕터의 DC 바이어스 특성을 고려한 대용량 DC-DC 컨버터의 손실계산

It is necessary to accurately predict converter losses for optimized design of a high-power DC-DC converter. The losses of switching devices and inductor among the elements of the converter take significantly greater proportion. The current ripple will be determined by the size of the inductance and this inductance value varies depending on the DC amount of inductor current. As the inductance changes according to load current, the change influences not only the inductor loss itself but also the total converter loss. In this paper, for more accurate design of a bi-directional DC-DC converter for 30㎾-class energy storage system, more accurate computational model is proposed considering inductance variation according to the load current change. The inductance changes using variable magnetic cores are verified and converter efficiency is tested through simulations and experiments.

Optimal Design of a DC-DC Converter for Photovoltaic Generation

This paper presents novel circuit topology of half-bridge soft-switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed, half-bridge high frequency PWM inverter with a high frequency planar transformer link PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode-equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC bus lines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, high switching frequency IGBTs can actually be selected in the frequency range of 40[㎑] under the principle of soft-switching. The performance evaluations of the experimental setup are illustrated practically.

Application of a Robust Fuzzy Sliding Mode Controller Synthesis on a Buck-Boost DC-DC Converter Power Supply for an Electric Vehicle Propulsion System

The development of electric vehicle power electronics system control, composed of DC-AC inverters and DC-DC converters, attract much research interest in the modern industry. A DC-AC inverter supplies the high-power motor torques of the propulsion system and utility loads of electric vehicles, whereas a DC-DC converter supplies the conventional low-power and low-voltage loads. However, the need for high-power bidirectional DC-DC converters in future electric vehicles has led to the development of many new topologies of DC-DC converters. The nonlinear control of power converters is an active research area in the field of power electronics. This paper focuses on the use of the fuzzy sliding mode strategy as a control strategy for buck-boost DC-DC converter power supplies in electric vehicles. The proposed fuzzy controller specifies changes in control signals based on the surface and knowledge on surface changes to satisfy the sliding mode stability and attraction conditions. The performance of the proposed fuzzy sliding controller is compared to that of the classical sliding mode controller. The satisfactory simulation results show the efficiency of the proposed control law, which reduces the chattering phenomenon. Moreover, the obtained results prove the robustness of the proposed control law against variations in load resistance and input voltage in the studied converter.

New high-frequency linked half-bridge soft-switching PWM DC–DC converter with input DC rail side active edge resonant snubbers

This study presents a new circuit topology of the active edge resonant snubber-assisted half-bridge soft-switching PWM inverter-type DC-DC high-power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high-frequency PWM inverter with a high-frequency planar transformer link in addition to input DC busline side power semi-conductor switching devices for the PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high-switching-frequency isolated gate bipolar transistor (IGBT) can be actually selected in the frequency range of 60-kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of the new converter topology is proved for low-voltage and large-current DC-DC power supplies as DC bus feeding from a practical point of view.

The New High Power Design of 8Ah Li-ion Battery for HEV Application

Researchers at The Industrial Technology Research Institute (ITRI) have developed a new 8Ah prismatic lithium battery cell with high current charge and discharge capability for use in hybrid electric systems applications. When 40 cells are combined in series, the system is capable of producing 144V which can be boosted up to 288V by using a high power DC-DC converter. The design results in (1) lower manufacturing and operating costs, (2) improved safety characteristics, (3) improved heat dissipation, and (4) improved battery management.Particular emphasis have been given to enhancing both discharge and charge performance of the cell by optimizing material selection and structure to lower the internal resistance of the system, thereby improving both performance and safety characteristics for the single cell. By carefully tuning the design of both electrodes, this second generation cell can provide 300A of continuous discharge current while maintaining the ability to meet the minimum requirement for pulse power characteristics. This provides 625W of discharge power and the ability to accept 500W of regenerative power when the system is operated with the State of Charge (SoC) between 50 and 70%. The cell has also been designed to meet the abusive physical requirements associated with hybrid vehicle applications.This paper highlights system requirements, describes the research and development process, and provides experimental test results for the 8Ah cell. The battery module design is also described.

Design and Development of High-Power DC–DC Converter for Metro Vehicle System

This paper presents the design and development of a transformer isolated high-power dc-dc converter. There are several design issues and challenges. In this paper, we focus on three major issues in high-power dc-dc converters. 1) An energy recovery passive snubber circuit and the selection of pulsewidth modulation control methods are first introduced to reduce the voltage spike and power loss across switching devices. 2) Interleaved winding method is then employed to reduce proximity effect in the transformer winding. 3) The voltage oscillation problem in the secondary rectifier diode is addressed, and solutions are provided.

A Novel Prototype of Duty Cycle Controlled Soft-Switching Half-Bridge DC-DC Converter with Input DC Rail Active Quasi Resonant Snubbers Assisted by High Frequency Planar Transformer

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.

Non-Dissipative Snubber for Rectifying Diodes in a High-Power DC-DC Converter

In a high output current DC-DC converter, most power dissipation comes from rectifying diodes. In this paper, a novel non-dissipative snubber is proposed for the rectifying diodes to reduce the power dissipation of the rectifying circuit. This snubber is applied to the center-tapped rectifying circuit in a full-bridge DC-DC converter. As a result, the efficiency has been improved to 91% on the prototype of 12V/80A output.

New high power DC-DC converter with loss limited switching and lossless secondary clamp

A new isolated high frequency high power DC-DC converter full bridge topology employing one resonant soft switching pole that is zero voltage switched and one phase-shifted hard switching pole with loss limited switching for primary switching is presented. The devices in the loss limited pole do not have resonant capacitors across them, but exhibit significantly lower losses than conventional hard switching as the energy dissipation is limited by the finite energy stored in the leakage inductance. This unique combination of zero voltage switching and loss limited switching reduces the switching loss in all primary devices to lower levels. Isolation is achieved by a coaxially wound high frequency transformer with ultra low leakage which increases throughput and efficiency. A novel nondissipative secondary rectifier clamp allows excellent control of reverse recovery energy. Converters that produce 128 kW at 25 kHz have been developed and are commercially available. As this topology exhibits complete control of all parasitic loss mechanisms, it can be easily scaled to higher power levels.

New high power, high performance power converter systems

A new, high performance, low cost power converter system architecture is proposed. The system consists of a main converter and a multifunctional load conditioner. The main converter deals with most of the power flow running at a low switching frequency. The load conditioner is designed at a much lower power level running at a high-switching frequency. The load conditioner can (1) act like a current source and inject harmonic currents required by the load; (2) act like an active resistor to provide damping to the main converter; and (3) for three-phase inverters, decouple the coupling sources in the main inverter model in the rotating coordinates to make the control loop design for the main inverter much easier. The concept has been proved by simulation and experimental results on a 150 kW high performance three-phase utility power supply prototype. The proposed system configuration can be used in high power DC-DC converters, inverters, PFC and UPS applications.

A comparison of high-power DC-DC soft-switched converter topologies

Many industrial and military applications are arising that require high power DC-DC conversion. These applications include shipboard, spaceborne, and transportation power systems. By employing new high voltage, high power IGBTs, along with modern soft-switching techniques, the switching frequency can be significantly higher than obtained using GTO devices, which in turn can lead to smaller, lighter weight, and potentially more cost effective equipment. The purpose of this paper is to compare the properties of several soft-switching converter topologies when used to achieve DC-DC conversion at high power and high voltage levels. As an example, a 100 kW transformer isolated converter with 700-1400 V DC input is designed with an estimated weight in the 200 pound range and an energy efficiency of 95%. >

Analysis and design of snubber circuits for high-power GTO DC-DC converters

This paper presents the analysis and the design of snubber circuits for high power DC-DC converters realized with gate turn off thyristors. These networks are fundamental for the safe operation of semiconductor devices but dissipate some energy. Means to minimize their losses are studied in this work. The snubber circuits described here are an evolution of the conventional C-snubber and L-snubber. The design of the snubbers is based upon circuits that permit the transfer of the trapped energy to the power source or to the load. Benefits, drawbacks and limits of each new proposed circuit are detailed and studied. Experimental results, obtained from a GTO laboratory prototype converter are reported. >

Investigation of Soft Switching on the Basis of Transient and Steady State Characteristic Analysis for Single-Ended High-Frequency Inverter.

A single-ended resonant type high frequency inverter using a Static Induction Transistor (SIT) described in this paper can be performed as a zero current switching (ZCS) operation without DC reactor.The SIT high frequency inverter is a low-cost one which has no transformer and it would be developed for a high intensity ultrsonic power supply and DC-DC converter. The circuit operation region not only ZCS but also ZCS • ZVS (zero current switching and zero voltage switching) were elucidated in the normalized plane. The characteristics of the inverter including the power control by frequency regulation were discussed. Furthermore the switching characteristics in the transientstate were investigated.These characteristics were substantiated on the basis of the numerical analysis and experimental results.

High-power switching regulator type DC-DC converters controlled by time-sharing high-frequency thyristor choppers with energy-storage and -transfer reactors

This paper is concerned with the latest technologies on high-power switching dc-dc converters controlled by time-sharing high-frequency thyristor chopper with energy -storage and -transfer reactor coupling links, which can operate over an ultrasonic chopping frequency region in the extent of 20KHz or more than 20KHz. The possible circuit configurations of new thyristor type switching step-up and down dc-dc converters relating to magnetic-power semiconductor devices and their unique features are described and discussed from a practical point of view. The general procedures of circuit analysis and performance evaluations to offer the desirable design data are presented, and the steady-state open-loop control characteristics and a closed-loop control policy are elucidated on the basis of the theoretical and experimental results. Thyristor type high-frequency switching step-up dc-dc converter using time-sharing control technique is also originally examined and discussed herein.