High-Efficiency DC-DC Converter with Resonant Current Doubler Circuit Topology -Zhuoran Cui -Electronics Department of Electrical and Photonics Engineering-Technical University of Denmark, DTU

 

High-Efficiency DC-DC Converter with Resonant Current Doubler Circuit Topology Zhuoran Cui Electronics Department of Electrical and Photonics Engineering Technical University of Denmark 

Abstract With the rapid development of data centers and increasing demands for computational capability, power converters featuring high power density and high efficiency are increasingly required. In this thesis, an LLC resonant converter combined with a current-doubler rectifier topology is selected to address high-current and low-voltage conversion scenarios, specifically for a DC-DC converter rated from 48 V down to 1.8 V. An integrated magnetic structure, combining the transformer with the current-doubler inductors, is designed and implemented. The converter is estimated to achieve an efficiency of approximately 96.7 %. Additionally, detailed PCB layout design and experimental verification are presented to validate the proposed approach.

LINK: https://orbit.dtu.dk/en/publications/high-efficiency-dc-dc-converter-with-resonant-current-doubler-cir/ 

Advances in Bidirectional DC-DC Converters for Future Energy Systems -Kevin Tomas Manez Research output: Book/Report › Ph.D. thesis-Technical University of Denmark.

 

Advances in Bidirectional dc-dc Converters for Future Energy Systems Author: Kevin Tomas Manez Supervisors: Zhe Zhang — DTU Elektro, Electronics Group Ziwei Ouyang — DTU Elektro, Electronics Group Department of Electrical Engineering Electronics Group Technical University of Denmark 

 Abstract 

The contemporary electricity grid is in the midst of a transformation in which decentralization of energy production is playing a key role. Spurred by the environmental concerns of traditional energy sources and the costs reduction of photovoltaic energy and energy storage systems (ESSs), energy decentralization is disrupting traditional models of energy generation. In addition, vehicle-to-grid technology has been presented as an opportunity to optimize the grid utilization. Considering that photovoltaic energy, energy storage systems and electrical vehicles operate in dc, the electricity network is following a trend of moving towards dc distribution in the form of multiple microgrids. Accordingly, technological advances that allow a simplified and flexible interconnection of microgrids with high energy efficiency are key enablers for the electricity grid transformation. In this regards, high efficiency power electronics interconnecting microgrids and integrating energy storage systems, constitute a main pillar for the development of microgrids and reaching high penetration of renewable energy sources. The state-of-the-art technologies in electrical power conversion are trending towards the utilization of dc solid-state transformers (SST) as interlinking converters between dc grids. Among the different power converter topologies implemented as SSTs, the series-resonant converter (SRC) has been extensively used, thanks to its load regulation characteristics in open-loop together and its soft-switching conditions for wide power ranges. This Ph.D. dissertation is divided into two parts. In the first part, the investigation of two-port and three-port SRCs in open-loop operation for dc SST applications is carried out and presented. The study focuses on the design considerations of distributed resonant tanks to improve the load regulations characteristics in open-loop operation at a fixed switching frequency and duty cycle. 

ORIGINAL LINK:  https://orbit.dtu.dk/en/publications/advances-in-bidirectional-dc-dc-converters-for-future-energy-syst/

Research Article Controlling Transformer Magnetizing Offset Current in Isolated Phase-Shift Full-Bridge Converters Using a Luenberger Observer -Angelika Neumann, Sönke Meynen, Ahmad Rahmoun, Daniel Ziegler, Thomas Kirchartz---Karlsruhe University of Applied Sciences, Karlsruhe, Germany

Controlling Transformer Magnetizing Offset Current in Isolated Phase-Shift Full-Bridge Converters Using a Luenberger Observer Angelika Neumann, Sönke Meynen, Ahmad Rahmoun, Daniel Ziegler, Thomas Kirchartz 

Abstract This paper proposes a flexible digital control scheme for isolated phase-shift full-bridge (PSFB) converters. The required transformer suffers from inevitable imbalance of magnetic flux resulting in an increased magnetizing DC-offset current that threatens system reliability due to saturation effects. The paper addresses two major issues of the occurrence of a magnetizing DC-offset current. First, caused by the change of duty cycle due to output power regulation and second caused by initial manufacturer tolerances of devices. In contrast to common methods the novel control scheme uses a Luenberger observer to estimate the magnetizing current requiring only simple measurement of transformer voltages without additional and lossy auxiliary networks. The observer model, in combination with a PI-controller, directly interventions the duty cycle and removes any DC-offset current resulting from both issues. A detailed deviation of the state-space model of the transformer and a subsequently design of the observer are presented. Simulation and experimental results on a PSFB prototype verify the principal functionality of the proposed control scheme to prevent transformer saturation. 

 International Transactions on Electrical Energy Systems Volume 2022, Article ID 9243429, 15 pages https://doi.org/10.1155/2022/9243429 

ORIGINAL LINK: https://onlinelibrary.wiley.com/doi/10.1155/2022/9243429 

Single-Stage Multi-Port Solid-State Transformer (SST) Based Medium-Voltage DC (MVDC) Interconnection System and Coordinated Control Strategies - Di Zhu, Chuang Liu, Jingyue Wang, Zhongchen Pei*, Chao Liu, Heyang Sun, Yu Jiang Northeast Electric Power UniversityDalian University of Technology

Single-Stage Multi-Port Solid-State Transformer (SST) Based Medium-Voltage DC (MVDC) Interconnection System and Coordinated Control Strategies Di Zhu, Student Member, IEEE, Chuang Liu, Member, IEEE, Jingyue Wang, Zhongchen Pei, Chao Liu, Member, IEEE, Heyang Sun, Yu Jiang 

Northeast Electric Power University

Dalian University of Technology

Abstract—Decentralized integration of distributed generation (DG) units and loads are increasing in the modern distribution grid. Maintaining the power flow and power quality within their accepted limits is a challenging task. This paper proposes a medium-voltage DC (MVDC) interconnection system based on the single-stage multi-port solid-state transformers (SST). First, the single-stage multi-port SST's coordinated control strategies and energy management method are discussed, aiming at the flexible power flow control between the utility grid, MVDC grid and the low-voltage AC/DC microgrid. Secondly, the MVDC controller parameters and SST passive components are optimized based on the impedance interaction characteristics between the two SSTs' MVDC ports, thereby enhancing the stability margin of the interconnected system. Then the operation modes of the interconnected system are defined. Finally, the effectiveness of the proposed operation modes and control strategy is verified through a 1-MW simulation platform, while a 1-kW scaled-down experimental prototype is built to further validate the single-stage multi-port SST and the MVDC interconnected system.

ORIGINAL LINK: https://orbit.dtu.dk/en/publications/single-stage-multi-port-solid-state-transformer-sst-based-medium-/ 

Bidirectional Grid-Forming Converter with Modified Voltage Control for Enhanced Power Dynamics Dos Santos Serra, Amiron Wolff; Nascimento, Khristian Augusto Freitas; De Matos, José Gomes; De Souza Ribeiro, Luiz Antonio; Savaghebi, Mehdi; Oliveira, Hércules Araújo Department of Engineering Technology and Didactics Federal University of Maranhão

Abstract— This paper proposes a control strategy for a bidirectional grid-forming converter, operating as a virtual synchronous generator, based on an improved voltage controller to enhance the dynamics of the active and reactive power loops. The theoretical analysis and real-time simulation results demonstrate the enhanced disturbance rejection of the proposed strategy, which is based on disturbance input decoupling. Furthermore, virtual impedance is used to limit the current injected by the converter during grid transitory situations.

ORIGINAL LINK: https://orbit.dtu.dk/en/publications/bidirectional-grid-forming-converter-with-modified-voltage-contro/