http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

A Survey of Wide Bandgap Power Semiconductor Devices

High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Energy storage systems (ESSs) are enabling technologies for well-established and new applications such as power peak shaving, electric vehicles, integration of renewable energies, etc. This paper presents a review of ESSs for transport and grid applications, covering several aspects as the storage technology, the main applications, and the power converters used to operate some of the energy storage technologies. Special attention is given to the different applications, providing a deep description of the system and addressing the most suitable storage technology. The main objective of this paper is to introduce the subject and to give an updated reference to nonspecialist, academic, and engineers in the field of power electronics.

Energy Storage Systems for Transport and Grid Applications

The main objective of this research work is to develop a new low-cost isolated three-level ac-dc power converter topology that is suitable for applications having high input ac voltages and high output currents; for example, hybrid (ac-dc) microgrids or offshore wind farms. Existing three-level converter topologies convert ac power to dc power while maintaining requirements set by international standards for power conversion. These types of converters have significant conduction losses due to high currents in the low-voltage side and high costs, particularly when using several devices in series or in parallel to achieve high-voltage and high-power levels. The proposed topology replaces the conventional three-level converters in the low-voltage side by only two controlled devices and four diodes while still maintaining the basic functionality of a three-level converter. Simulation results for a 87.5-kW case study and experimental results on a 250-W scale-down prototype demonstrate the feasibility of the proposed ideas.

A New Isolated AC-DC Power Converter Topology with Reduced Number of Switches for High-Input Voltage and High-Output Current Applications

This work presents an optimization algorithm for the design of isolated Dual-Active Bridge (DAB) converters using parallel power modules, in which volume, power density and number of switching devices are selected to achieve an specific optimal point of operation for giving input/output voltages and power. This point of operation is selected based on the maximum switching frequency that can be used for possible maximum power and minimum volume to obtain the desired power density. The maximum power can be selected based on the number of switching devices that are needed for a giving output power and the volume is based on the design of the magnetic components, such as inductors and transformer. The proposed design algorithm selects the magnetic components and number or switching devices based on an optimal point of operation that maximizes efficiency and minimizes volume to obtain the best volume-to-losses relation for a giving switching frequency.

Optimization Design Algorithm for Dual-Active Bridge Converters Using Parallel Power Modules

Rooftop single-phase PV smart inverters in residential distribution systems are becoming more common throughout the United States. As a result, utilities are experiencing increases in the numbers of operations for voltage regulators and on-load tap changers under certain operating conditions for high PV penetration levels which may lead to reduced maintenance intervals. However, PV smart inverters can be controlled under different functions or operating modes with some potentially reducing the number of operations of voltage regulators and thus, increasing maintenance intervals. To this end, three selected functions of PV smart inverters are evaluated on a case study based on a 13.8-kV modified IEEE 37-bus system controlled under conservation voltage reduction and integrated Volt/VAr using EPRI OpenDSS™ software package to demonstrate that some functions do positively assist in voltage regulation and reactive power control.

Evaluation of Single-Phase PV Smart Inverter Functions in Unbalanced Residential Distribution Systems

The thermal resistance of a power modules is critical to determine the safe operating area and by extension, application specifications. Traditional methods of thermal characterization determine steady-state thermal resistance values. However, the system transient thermal response is of equal importance due to the conceptual RC thermal network that comprises the module, determining dynamic thermal behavior. Traditionally, this thermal impedance has been extracted using complex methods and only describes thermal impedance as a lumped average. This paper proposes an infrared-based observation method that utilizes image topography to determine die-to-die thermal impedance. The model can be used to predict detailed die response under different system level loads. Intra-die thermal coupling is a feature of the modeling technique to detect hot-spots and abnormalities. Experimental results are presented to validate the claims of this work.

Sliding Window-Based Thermal Topography Determining Thermal Impedance and Thermal Coupling

DC-Link filtering capacitors occupy a significant volume in DC-DC-AC power conversion unit (PCU) for electric vehicle (EV) applications, where manufacturing costs and power density are related metrics and are important. Typically, the DC-Link capacitor is sized electrically based on the desired voltage ripple and rms current capacity, with the latter being the ultimate deciding factor in the capacitor overall physical volume. This paper proposes a synchronous modulation strategy that matches the current of an interleaved DC-DC converter in discontinuous conduction mode (DCM) with that of the inverter-drawn current to significantly reduce the RMS current ripple in the DC-link capacitor, and thus enabling a volumetric reduction when considering system design and increasing capacitor lifetime. Simulation and experimental results are presented to validate the claims of this work.

Juan Carlos Balda

Papers

A New Isolated AC-DC Power Converter Topology with Reduced Number of Switches for High-Input Voltage and High-Output Current Applications

Optimization Design Algorithm for Dual-Active Bridge Converters Using Parallel Power Modules

Evaluation of Single-Phase PV Smart Inverter Functions in Unbalanced Residential Distribution Systems

Sliding Window-Based Thermal Topography Determining Thermal Impedance and Thermal Coupling

Minimizing DC-Link Capacitor RMS Current in Power Conversion Units Through Synchronous Operation