High Power DC-DC Converter Research Articles

Minimum current stress control strategy for three degree of freedom three-phase dual active bridge DC-DC converter

Compared to single-phase dual active bridge (1p-DAB) DC-DC converters, three-phase dual active bridge (3p-DAB) DC-DC converters have advantages such as high single machine power, high power density, small filtering capacitance, and are more suitable for high-voltage situations. Therefore, they have good application prospects in DC transmission and industrial high-power DC-DC converters. However, under traditional single-phase shift (SPS) control, especially in the low power range, there is a large reactive current and severe soft switch loss. This article adopts an asymmetric modulation strategy for its larger reactive power, which reduces its reactive power in the low power range with more degrees of freedom and improves the efficiency of power transmission. Taking current stress as the optimization objective, the KKT algorithm is used to solve, and the corresponding analytical solution is ultimately obtained. Finally, a simulation is built by using MATLAB software to verify the feasibility of the proposed solution.

Design of continuous-duty high-power converter for multi-purpose welding applications

One large-current high-power full-bridge DC-DC converter is often used to cater several multi-characteristic welding loads. The load could be a welding arc or a conductive molten flux. The contour of operating point (voltage-current) of each load type is different. The converter often operates under complex light-load conditions. The design of such high power continuous-duty converter needs to meet three objectives – desired control performance, high across-the-load efficiency, and superior thermal management. To address the thermal issues, this article proposes to use parallel-connected converter modules. It helps distribute the power loss over larger component base; increased surface area would assist the heat removal process. For high operating efficiency, this article proposes superior component engineering in each module. And, for high across the load efficiency, this article proposes to enable or disable an efficient converter module based on the current demand. It means each converter module is equipped to feed the connected load in stand-alone mode. For reduction of power loss, this article elaborates the role of each critical component. The distribution of heat loss would be optimally shared if the current sharing by converter modules is equal, but it needs to be compatible to the dynamic behavior of multi-input process loads. This research proposes and practically validates that single PWM-controller driven parallel-connected converter-modules are not only compatible to process dynamics, the idea would achieve proper current sharing among similar components.

Simulation optimal and design of 3-kW DC-DC converter for pure electric vehicles

There are significant differences between pure electric vehicles and traditional fuel vehicles. High-power converters are required to meet the increased energy consumption requirements of loads within pure electric vehicles. A high-power integrated DC-DC converter is designed to meet the requirements of pure electric vehicles. First, the characteristics of LLC resonant converters are analyzed, and a fuzzy adaptive PID frequency conversion phase-shift soft switching control strategy is proposed. Second, the fuzzy controller is designed based on the MATLAB toolbox based on the characteristics of electric vehicle converters. Then, in order to further improve the efficiency of the converter, a planar transformer is proposed and optimized. It is found that with the increase in the switching frequency, the loss is smaller, which is more conducive to improving the efficiency. Simulation results show that zero-voltage switching and zero-current switching can be realized by using the proposed control strategy, and experimental results show that the proposed strategy is significantly more efficient under non-heavy-load conditions. The minimum and maximum efficiency values are 92% and 97.38%, respectively. The high-power converter ensures the normal operation of the load of pure electric vehicles. This work provides a method for developing high-power DC-DC converters and improving efficiency.

A Scalable DC/DC Converter Topology With Modularized Energy Storage for High Energy Physics Applications

This paper presents the design and control of a high-power modular DC-DC converter for electromagnets used in high energy physics applications. The fundamental building modules, herein called bricks, can either be connected to the grid or to separate energy-storage components. The proposed modular converter enables independent power flow control among the bricks under control that is agnostic to mission profiles. In particular, the proposed converter design and control allow for independent control of currents delivered from each brick, while respecting the total voltage constraints, and losses optimisation of the converter without compromising the desired electrical performance. In addition, the cost potential of the converter is briefly analysed. The performance of the proposed modular converter is validated experimentally on a full-scale lab prototype rated at 800 kW. The proposed converter demonstrates how separating the total storage into a number of storage bricks can be beneficial to adapt the design of a modular converter to a large range of profiles and operating constraints. It is shown that up to 30% cost savings can be achieved by eliminating converter components in the storage and grid connection, while the converter performance on the load is maintained and the same amount of energy is recycled.

Adaptive online auto-tuning using Particle Swarm optimized PI controller with time-variant approach for high accuracy and speed in Dual Active Bridge converter

<abstract> <p>Electric vehicles (EVs) are an emerging technology that contribute to reducing air pollution. This paper presents the development of a 200 kW DC charger for the vehicle-to-grid (V2G) application. The bidirectional dual active bridge (DAB) converter was the preferred fit for a high-power DC-DC conversion due its attractive features such as high power density and bidirectional power flow. A particle swarm optimization (PSO) algorithm was used to online auto-tune the optimal proportional gain (<italic>K<sub>P</sub></italic>) and integral gain (<italic>K<sub>I</sub></italic>) value with minimized error voltage. Then, knowing that the controller with fixed gains have limitation in its response during dynamic change, the PSO was improved to allow re-tuning and update the new <italic>K<sub>P</sub></italic> and <italic>K<sub>I</sub></italic> upon step changes or disturbances through a time-variant approach. The proposed controller, online auto-tuned PI using PSO with re-tuning (OPSO-PI-RT) and one-time (OPSO-PI-OT) execution were compared under desired output voltage step changes and load step changes in terms of steady-state error and dynamic performance. The OPSO-PI-RT method was a superior controller with 98.16% accuracy and faster controller with 85.28 s<sup>-1</sup> average speed compared to OPSO-PI-OT using controller hardware-in-the-loop (CHIL) approach.</p> </abstract>

A Review of Magnetic Core Materials, Core Loss Modeling and Measurements in High-Power High-Frequency Transformers

High-frequency transformers (HFTs) are the indispensable component in isolated high-power dc-dc converters which have been the basic building blocks for solid-state transformers. To ensure high efficiency, high power density and high reliability, careful selection, design, modeling and evaluation are necessary for the magnetic core of an HFT. However, due to the nonlinear characteristics and the complex physical mechanism, magnetic cores have always been regarded as the focus and difficulty. This paper systematically reviews magnetic core materials commonly used in HFTs, core loss modeling methods based on classical Steinmetz equation (SE), and advanced core loss measurement techniques. Pros and cons for the magnetic materials, modeling and measurement methods are comprehensively analyzed and summarized to provide a sufficient application insight.

Lithium-ion battery modeling under high-frequency ripple current for co-simulation of high-power DC-DC converters

Studying the output response of lithium-ion batteries under high-frequency ripple current is important for the co-simulation and optimal design of high-power DC-DC converters using IGBTs. However, this influence has not been sufficiently investigated. In this paper, seven equivalent circuit models which include integer and fractional order models are used to simulate the high frequency characteristics of lithium-ion batteries. Thirteen experiments are designed and implemented on three test platforms, including a self-designed DC-DC platform for triangular wave. These experiments consist of average currents of different amplitudes, ripple currents of different types, amplitudes and frequencies. Unlike previous research, the current excitation and voltage response of high frequency ripple are obtained by separating the short and long time scale signals. The equivalent circuit model components are selected based on the frequency domain characteristics of the impedance spectrum. The HMPSO method is employed to implement the parameter identification and simulation analysis of the high frequency model under time domain data. By contrast, the first-order RL model is selected as the preferred choice through modeling and co-simulation. The complexity of the model and co-simulation time is reduced while maintaining voltage accuracy. For the case presented in this paper, the co-simulation time of R(RL) can be reduced by 11.3 % and 30.2 % compared to the RL and R(RL)(RL) models.

Analysis of on-state static and dynamic transients of high voltage 4H-SIC Merged-PiN-Schottky diode

The 4H-SiC vertical Merged-PiN-Schottky (MPS) diodes are attractive power devices with potentials to be used in high-power DC-DC converter with high voltage ratings in the range of 1.7 kV and high operating temperatures, as an alternative to Junction Barrier Schottky (JBS) diodes. This paper reveals the dynamic switching performance and the static characteristics of the SiC MPS diode in comparison with the Silicon PiN diodes and SiC JBS diodes through a wide range of experimental measurements. It shows the superior switching performance of the SiC MPS and JBS diodes due to the absence of the reverse recovery charge. However, it is shown that this is at the cost of the large on state voltage especially at high currents and high temperatures and the increasing forward voltage during the conduction state. As the temperature dependence of forward voltage of Silicon PiN diodes is negative, they are prone to thermal runaway when connected in parallel. Such destructive consequence is also hold for single SiC MPS diode as it is shown that the lack of conductivity modulation leads to a surge of forward voltage in the on-state.

Solar PV Fed DC Microgrid: Applications, Converter Selection, Design and Testing

In this research article, major applications which use solar PV fed DC microgrid for either their routine operation or gain additional advantages over existing electrical power architecture are elaborated. The role of power converters in interfacing the input with the required output is highlighted. The advantages of solar PV fed DC microgrid are demonstrated by designing and testing a non-isolated high gain high power (HGHP) DC-DC converter to meet the DC distribution voltage level. The proposed converter is synthesized by using hybrid combination of three-phase interleaved boost converter (IBC) with voltage lift technique along with coupled inductors (CIs) and voltage multiplier cell (VMC). The proposed concept is practically demonstrated and the adopted design techniques are validated using simulation and experimentation. The proposed converter with 60V/1.1kV, 100kHz and 3kW rating operates at 92.3% full-load efficiency under practical conditions. Due to the gain extension techniques adopted, the switches used in the proposed converter are subjected to a voltage stress which is only 36% of the output voltage. Due to interleaving technique, the input current ripple and the current stress on the switches are only 15% and 33% of the input current respectively. Key performance parameters of this converter are thoroughly investigated and benchmarked with some state-of-the art converters to appreciate the salient features of the presented converter. The ability to yield higher voltage gain at safe duty ratio, high power handling capacity, low voltage and current stresses on the power switches are the main advantages of the proposed converter.

Efficiency-Optimized Modulation Scheme for Three-Phase Dual-Active-Bridge DC–DC Converter

The three-phase dual-active-bridge (3p-DAB) converter features isolated bidirectional power flow, soft-switching capability, reduced transformer, and filter volume. Thus, it is a promising topology for high-power dc-dc conversion. However, when it operates under light load or far from the unitary voltage ratio, the resulting converter efficiency is degraded by the loss of soft-switching capability or increased rms current. To overcome this issue, this article presents an optimized hybrid modulation scheme designed to minimize the total power losses of a 3p-DAB converter under load and voltage variations. An optimization scheme, including switching losses, conduction losses, and core losses, selects the best operation mode for a desired operating point between a novel zero-vector modulation and the traditional phase-shift modulation. An experimental prototype operating at a switching frequency of 100 kHz and a maximum output power of 1 kW was built to validate the theoretical analysis. The results show substantial gain in the converter efficiency, especially at low power or nonunity voltage ratio operating points.

Reconfigurable Hybrid Energy Storage System for an Electric Vehicle DC–AC Inverter

Hybrid energy storage systems using battery packs and super capacitor (SC) banks are gaining considerable attraction in electric vehicle (EV) applications. In this article, a new modular reconfigurable multisource inverter (MSI) is proposed for active control of energy storage systems in EV applications. Unlike the conventional approaches, which use massive high-power dc-dc converters with bulk magnetic elements for combining SC banks and battery packs, the new approach utilizing the MSI offers magnetic-less structures. This reduces the weight and volume of the power electronics interface and offers simple control. Along with the proposed MSI, a space vector modulation technique and a deterministic state of charge (SOC) controller are also introduced for the control of the switching actions and operation of the SC bank. Simulations using MATLAB/Simulink and experimental results on a scaled down lab prototype are studied to assess the concepts.

A New Efficient Step-Up Boost Converter with CLD Cell for Electric Vehicle and New Energy Systems

An increase in demand for renewable energy resources, energy storage technologies, and electric vehicles requires high-power level DC-DC converters. The DC-DC converter that is suitable for high-power conversion applications (i.e., resonant, full-bridge or the dual-active bridge) requires magnetic transformer coupling between input and output stage. However, transformer design in these converters remains a challenging problem, with several non-linear scaling issues that need to be simultaneously optimized to reduce losses and maintain acceptable performance. In this paper, a new transformer-less high step-up boost converter with a charge pump capacitorand capacitor-inductor-diode CLD cell is proposed using dynamic modeling. The experimental and simulation results of the proposed converter are carried out in a laboratory and through Matlab Simulink, where 10 V is given as an input voltage, and at the output, 100 V achieved in the proposed converter. A comparative analysis of the proposed converter has also been done with a conventional quadratic converter that has similar parameters. The results suggest that the proposed converter can obtain high voltage gain without operating at the maximum duty cycle and is more efficient than the conventional converter.

Modeling and Design of a Medium-Frequency Transformer for High-Power DC-DC Converters

Modeling and Design of a Medium-Frequency Transformer for High-Power DC-DC Converters

Multiport energy gateway

Medium-voltage-direct-current collection and distribution grids are being considered for emerging applications, and require enabling power electronic technologies. Medium-voltage high power DC-DC converters are one of the solutions that will play an important role in future energy systems. This study presents a novel bidirectional multiport power electronic converter, interfacing medium-voltage and low-voltage distribution grids while integrating distributed energy storage elements, such as batteries and super-capacitors. The multiport energy gateway concept is based on a modular input-series output-parallel topology includes medium frequency transformer for the galvanic isolation, and combines open-loop and closed-loop operated converter stages. Comprehensive converter design aspects and operating principles are presented and discussed considering representative cases of studies. The validity of the approaches is proved by simulation and experimental results obtained on a small scale prototype.

Constant voltage/current with slowly rising control for high power DC-DC converter based on FPGA digital control

Constant voltage/current with slowly rising control for high power DC-DC converter based on FPGA digital control

Design of SiC-Based DC-DC Converters for Future Offshore Wind Power Applications

This work is a contribution to the design of high-power DC-DC converters for future wind power applications by use of new semiconductors made of silicon carbide. First, the application is introduced, that is selected for high performance SiC devices. The design methodology is presented and validated with measurements of a physical prototype.

Hybrid modular converter for DC microgrids

A novel non-isolated high step-up high-power DC-DC converter based on coupled inductor (CI) and voltage multiplier cell (VMC) for renewable energy DC microgrids is presented in this study. A hybrid combination of three-phase interleaved boost converter with three CIs is chosen to reduce the current ripple at the input and meet the high-power requirement. Three VMCs connected at the secondary side of the CIs serve as gain extension cells. The voltage stress experienced by the switches is only a fraction of the output voltage as the gain extension is mainly achieved at the secondary side of CIs. Practical results obtained from the proposed converter which operated from a 60 V input and provided an output voltage of 1.1 kV while delivering 3 kW of output power prove the correctness of the design details and validate the proposed concept.

High-gain-high-power (HGHP) DC-DC converter for DC microgrid applications: Design and testing

The use of green energy sources to feed DC microgrids is gaining prominence over traditional centralised AC systems. DC microgrids are characterised by the use of intermediate DC-DC converter which acts as power conditioning units. Hence, the choice of an appropriate DC-DC converter becomes significant as the overall system efficiency is strongly dependent on the converter’s performance. This paper proposes a novel high gain high power (HGHP) DC-DC converter for DC microgrid, which is of one of the significant step forward in the development of DC microgrids. The suitability of the proposed HGHP DC-DC converter is demonstrated by experimental tests of the 60V/1.1kV, 3kW converter; test results validate the converter’s suitability for DC distribution. A significant number of performance parameters of the proposed converter is compared with state of the art converter topologies demonstrating the superior capabilities of the proposed converter. This paper also portrays the potential benefits that could be reaped by trending towards DC instead of existing AC system. The advantages and challenges to be confronted in the foreseeable future while implementing sustainable DC microgrids are also highlighted. Finally, this paper encapsulates renewable energy fed DC microgrid system as an appropriate, technically feasible, economically viable and competent solution for efficiently utilising the sustainable energy sources.

A High-Power DC-DC Converter Topology for Battery Charging Applications

A DC-DC converter that can be applied for battery chargers with the power-capacity of over 7-kW for electric vehicles (EVs) is presented in this paper. Due to a new architecture, the proposed converter achieves a reduction of conduction losses at the primary side by as much as 50% and has many benefits such as much smaller circulating current, less duty-cycle loss, and lower secondary-voltage stress. In addition, its power handing capacity can be upsized easily with the use of two full-bridge inverters and two transformers. Besides, all the switches in the converter achieve zero-voltage switching (ZVS) during whole battery charging process, and the size of output filter can be significantly reduced. The circuit configuration, operation, and relevant analysis are presented, followed by the experiment on a prototype realized with a 7-kW charger. The experimental results validate the theoretical analysis and show the effectiveness of the proposed converter as battery charger.

Effective Energy Management in Electric Vehicles using High-Power Bidirectional DC-DC Converter

The Plug in Hybrid Electric Vehicle has become passion today for its less emission of gasoline and reduced fuel price. PHEVs have battery to be recharged from a standard power vent. It is an unexpected load in residential power system. Uncoordinated charging of many PHEVs at a time creates a sudden change in load demand of grid causes a potential drop in power system and power loss. PHEV consumes more energy from the grid. This report offers a technique to trim power consumption from the power system. A high power, bidirectional DC-DC converter is introduced in PHEV to charge the battery when the motor in PHEV acts as a generator. In this paper, Intelligent fuzzy logic controller is proposed as charging controller of the battery. Performance of the proposed system is simulated using Matlab and compared to the conventional controls. This paper proposes a technique to reduce load demand on distribution grid.