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/ 

Green & Black-starting HVDC-connected Offshore Wind Power Plants: Grid forming control, Energization transients and Islanding capabilities - Anubhav Jain

 

Summary

 Green energy transition is the most urgent need of the hour to curb the rising impact of global warming. The carbon-neutral energy system of the future will have electricity as its backbone, which requires a domination of renewable sources and long distance interconnections. However, such a transformation brings forth a massive penetration of power electronic converters to allow for flexibility in operation that is essential for efficient and cost-effective grid usage. This paradigm shift will make future power grids very different from the current system resulting in a highly dynamic environment that poses a risk to power system stability. Coupled with the declining strength of the network, it has the potential to increase the impact of severe network disturbances and give rise to challenges for the containment of voltages and frequency excursions, ultimately triggering wide-area blackouts. Since conventional synchronous generation is being phased out, the responsibility to maintain power system stability and provide network restoration services must be taken up by alternate sources of generation. Being one of the fastest growing renewable energy sources in the world, offshore wind is deemed a prime candidate.

ORIGINAL LINK: https://orbit.dtu.dk/en/publications/green-amp-black-starting-hvdc-connected-offshore-wind-power-plant/ 

A Multi-Loop Control for Grid-Forming Converters with Enhanced Dynamics Amiron Wolff Dos Santos Serra, Luiz Antonio De Souza Ribeiro, Mehdi Savaghebi-Institute of Electrical Energy Federal University of Maranhão São Luís – MA, Brazil-Department of Engineering Technology Technical University of Denmark (DTU)-

 

A Multi-Loop Control for Grid-Forming Converters with Enhanced Dynamics Amiron Wolff Dos Santos Serra, Luiz Antonio De Souza Ribeiro, Mehdi Savaghebi Department of Engineering Technology and Didactics

 2024 Energy Conversion Congress & Expo Europe - Darmstadt, Germany Duration: 2 Sept 2024 → 6 Sept 2024

 Abstract This paper proposes a control strategy for grid-forming converters based on a cascade control scheme with current and voltage controllers and an outer loop to control the injected active and reactive power. The analysis demonstrates the increased disturbance rejection capability of the current controller, and the improved loop gain in the low-frequency region of the voltage controller from the concept of disturbance input decoupling. Simulation results prove the effectiveness of the proposed strategy. 

ORIGINAL LINK: https://orbit.dtu.dk/en/publications/a-multi-loop-control-for-grid-forming-converters-with-enhanced-dy/ 

Advances in High Frequency Inductor Design for Power Converter Bima Nugraha Sanusi Ph.D.Thesis Technical University of Denmark.

 

Advances in High Frequency Inductor Design for Power Converter Bima Nugraha Sanusi Ph.D.Thesis Technical University of Denmark. 

 Abstract  

The Power Sources Manufacturers Association roadmap identifies high-efficiency and high-power-density end-use of electricity as one of the key challenges to increase the economic growth rate with a minimal environmental impact. The challenge in realizing smaller, faster, and in turn greener power supplies is the integration of magnetic materials that can operate efficiently at high frequency. The most successful work will involve magnetic material development, optimization of magnetic component designs, and consideration of fabrication constraints. This project primarily aims for a high-efficiency and high-power-density power management (DC/DC converter) from the USB-C port to the battery within the next generation of fast-charging smartphones or other portable electronic devices. This thesis hypothesizes that employing superparamagnetic nanoparticles material, which has high permeability and negligible hysteresis loss, in high-frequency inductor design can enable high-efficiency and high-power-density converter. The focus of this thesis will be on the magnetic material characterization and the inductor design. The first step is to establish a baseline prototype with state-of-the-art magnetic material. Multi-phase Zero Voltage Switching (ZVS) Buck converter is the selected topology to achieve high power density. A novel utilization of 4-leg magnetic core is proposed as the integrated inductor. From the constructed inductor model and semiconductor losses calculation, the design trade-off is analyzed. The optimal switching frequency is found to be around 2 MHz in this case, which is when the core material performance factor peaks. As proof of concept, a highly compact prototype, featuring stacked PCB solution is built. The input voltage ranges from 6 V to 12 V and the converter can deliver up to 10 A at 4 V output. The converter reaches a nominal efficiency of 88% and has a power density of 301 W/in3. The second step is to build a platform for magnetic core characterization, in particular the core loss. Mutual inductance compensation method is employed in the measurement circuit to reduce sensitivity to phase errors. An addition to the circuit is proposed in this work to make easier DC bias generation. This platform is used to study the core losses behavior at high frequency with superimposed DC bias in ferrite. The tested MnZn ferrite has a nominal relative permeability of 1500 and 800, which was tested at frequency from 500 kHz to 3 MHz. The measurement results are explained thoroughly with three controlling parameters: excitation frequency, AC flux density amplitude, and DC bias. Furthermore, an improved Steinmetz Premagnetization Graph and Artificial Neural Network are used to create core loss prediction model. The measurement data and built model can be accessed online for use by another magnetics designer. The third step is to analyze the switching transition in multi-phase half-bridge circuit with coupled inductors. It was found that the coupled inductors can achieve or maintain ZVS in the cases where non-coupled inductors cannot. Moreover, the coupled inductors can reduce the required deadtime to achieve ZVS. This benefit comes from the increased amplitude and frequency of resonant voltage in the presence of coupled inductors. The impact is quantified, analyzed, and verified in this thesis. 

ORIGINAL LINK: https://orbit.dtu.dk/en/publications/advances-in-high-frequency-inductor-design-for-power-converter/