Isolated Single-stage Three-phase AC/DC Converter using Bidirectional Switches Ramandeep Narwal† , Isaac Wongx , Subhashish Bhattacharya‡ , B. Jayant Baliga§ and Douglas C. Hopkins∗ FREEDM Systems Center, Department of Electrical and Computer Engineering North Carolina State Univers

 

Isolated Single-stage Three-phase AC/DC Converter using Bidirectional Switches Ramandeep Narwal† , Isaac Wongx , Subhashish Bhattacharya‡ , B. Jayant Baliga§ and Douglas C. Hopkins∗ FREEDM Systems Center, Department of Electrical and Computer Engineering North Carolina State University Raleigh, NC 27695, USA

 Abstract—The advent of the SiC Bidirectional FET (BiDFET), a monolithic 1.2 kV bidirectional switch, has rendered the single-stage three-phase AC/DC converter topology a promising approach for implementing AC/DC converters. This topology, which integrates a full-bridge converter with a single-phase to three-phase matrix converter via a high-frequency transformer, is particularly suitable for applications requiring galvanic isolation, buck-boost functionality, and bidirectional power flow. The single-stage design eliminates the need for bulky and unreliable electrolytic capacitors, and utilizes a single magnetic component for power transfer. In the matrix converter, bidirectional switches, which were traditionally implemented using combinations of multiple semiconductor devices such as MOSFETs, IGBTs, and diodes, can now be realized using the single-chip solution, BiDFET. This advancement leads to a lower switch count, compact converter implementation, with lower inductance commutation cells, thereby enhancing the overall efficiency and compactness of the system. The paper presents a unified model of the converter, considering all control parameters, including the duty cycles and phase shift of transformer voltages. Detailed expressions for power transfer, transformer currents, and currents at AC and DC ports are provided. Additionally, the paper outlines the conditions necessary for soft-switching of all switches and the commutation schemes required for the practical implementation of the matrix converter modulation scheme. A hardware prototype of a 10 kW, 480 VRMS, LL/ 800 V AC/DC system has been developed, and experimental results are presented to demonstrate its performance.

VIEW FULL PAPER: https://www.osti.gov/servlets/purl/2324747

Planar Transformer Systems for Modular Power Electronics in Long-Haul, Low-Cost PV Systems-Mike K. Ranjram Title: Assistant Professor-Arizona State University

 

Planar Transformer Systems for Modular Power Electronics in Long-Haul, Low-Cost PV Systems Mike K. Ranjram Title: Assistant Professor-Arizona State University

 Background The aim of this project is to develop and verify a new approach to designing medium-voltage (MV) planar transformers for emerging, utility-scale, modular PV systems. This approach considers these MV planar transformers as systems rather than as components. This means they can comprise multiple individual magnetic cores and printed circuit boards (PCBs) which can be distinctly organized both electrically and physically to achieve maximum performance. Central to this approach is that lowcomplexity winding stack-ups are leveraged which simplify primary-to-secondary insulation requirements, mitigate the need for interleaved windings, and aid in streamlining manufacturing and greatly reducing cost. Additionally, these systems dramatically expand the available material choices for the PCB by significantly reducing their required dielectric strength. This is a key driver of low-cost PCBs and mitigates sensitivity to supply chain changes in any particular material. The three key aspects of a medium voltage planar transformer in a solar PV application are its: (1) isolation capability, (2) cost, and (3) loss. This project comprehensively explores each of these three facets and we ultimately advance planar transformers having higher isolation capability, much lower cost, and lower loss than the state-of-the-art, at a comparable and lower volume. In this section, we provide background on each of these three key facets of the design.

VIEW FULL PAPER:https://www.osti.gov/servlets/purl/2452814

Design and Qualification of a 100 kW Three-Phase SiC-Based Generator Rectifier Unit Rated for 50,000 ft Altitude Jiewen Hu, Member, IEEE, Xingchen Zhao, Student Member, IEEE, Lakshmi Ravi, Student Member, IEEE, Rolando Burgos, Senior Member, IEEE, Dong Dong,

 

Design and Qualification of a 100 kW Three-Phase SiC-Based Generator Rectifier Unit Rated for 50,000 ft Altitude Jiewen Hu, Member, IEEE, Xingchen Zhao, Student Member, IEEE, Lakshmi Ravi, Student Member, IEEE, Rolando Burgos, Senior Member, IEEE, Dong Dong, Senior Member, IEEE, Richard Eddins, Sriram Chandrasekaran and Saeed Alipour 

VIEW FULL PAPER: https://www.osti.gov/servlets/purl/2446561

Abstract—Featuring higher blocking voltage, smaller parasitic elements, faster switching speed, and a more compact package, wide-bandgap semiconductor devices like Silicon Carbide devices (SiC), can enable compact aircraft generator-rectifier units (GRUs) thus making them highly desirable. Yet, the combination of the increased voltages, high power density, and the lower pressure environment associated with aircrafts can pose a significant threat to the converter operation due to the increased sensitivity to electric field (E-field) intensity inside the GRU components and their assembly. To this end, a comprehensive design and qualification of a 100 kW three-phase SiC-based GRU rated for a flight altitude of 50,000 ft (11.6 kPa) is presented in this paper. First, an insulation coordination that based on Paschen-curve is proposed to improve the power density. High E-field areas of the GRU are determined and preemptively solved with the use of an E-field control methodology to prevent partial discharge (PD) under normal operating conditions. Second, the gate-driver and EMI filter components are optimized for operation at 70 kHz. Finally, the insulation design is qualified through low-pressure PD tests, and it is verified that the unit successfully operates at rated conditions to achieve 33.3 kW/l power density, 99.2 % efficiency, and PD-free operation at 50,000 ft.

Optimal Design of MHz LLC Converter for 48V Bus Converter Application Yinsong Cai, Student Member, IEEE, Mohamed H. Ahmed, Student Member, IEEE, Qiang Li, Member, IEEE, and Fred C. Lee, Life Fellow, IEEE

Optimal Design of MHz LLC Converter for 48V Bus Converter Application Yinsong Cai, Student Member, IEEE, Mohamed H. Ahmed, Student Member, IEEE, Qiang Li, Member, IEEE, and Fred C. Lee, Life Fellow, IEEE

 Abstract—Intermediate bus architecture employing 48V bus converters is widely used in power supply applications. With the rapid increase of demanded power by these loads, higher efficiency and power density are driving better performance power management solutions. In this paper, a Gallium Nitride (GaN) based design of a two-stage solution is proposed. The first stage is a multi-phase Buck for regulation. The second stage is an LLC converter with fixed switching frequency for isolation. The detailed design and optimization of the LLC converter are studied. To achieve high power density and high efficiency, the transformer design becomes critical at MHz frequency. The matrix transformer concept is applied and a merged winding structure is used for flux cancellation, which effectively reduces the AC winding losses. A novel primary termination and via structure is proposed, resulting in great loss reduction. In addition, to study the current sharing of parallel winding layers, a 1-Dimensional analytic model is proposed, and a symmetrical winding layer scheme is used to balance the current distribution. Finally, the prototype for the two-stage bus converter is developed, with the peak efficiency of 96% and power density of 615W/in3.

 VIEW FULL PAPER: https://www.osti.gov/servlets/purl/1799217

Twelve-Step Voltage Source Inverter: A Three-Phase Six-Levels Inverter Using Planar Transformers Haitham KANAKRI, Euzeli Cipriano DOS SANTOS JR., and Maher RIZKALLA

 

Twelve-Step Voltage Source Inverter: A Three-Phase Six-Levels Inverter Using Planar Transformers Haitham KANAKRI, Euzeli Cipriano DOS SANTOS JR., and Maher RIZKALLA 

 Abstract—Multi-level inverters (MLIs) are becoming increasingly popular in high-speed motor drive systems for modern electric aircraft applications. However, two significant limitations are associated with current MLIs technology: (1) the high switching losses due to the high carrier switching frequency and (2) the complex modulation schemes required to maximize the DC source utilization. Consequently, the development of new topologies to mitigate these limitations is imperative for the rapid advancement of future electric aircraft systems. This paper introduces a six-level twelve-step inverter (TSI) that utilizes twelve switches and three planar high-frequency transformers. Implementing the proposed configuration ensures maximum DC source utilization, with a peak phase voltage of 5Vdc / 3. The proposed solution presents less semiconductor losses than the conventional MLIs, surpassing conventional MLIs, associated with neutral point clamped (NPC), flying capacitor (FC), and cascaded H-bridge (CHB). Experimental results demonstrate the TSI’s operation under static and dynamic conditions and its capability to function in three different modes: three-step, six-step, and twelve-step operations. The paper also offers a comprehensive design of the proposed planar transformer, supported by theoretical analysis, finite element analysis (FEA), and experimental validation.

VIEW FULL TEXT WEB: Page 263-273

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