Article
Energy & Fuels
Matheus Sene Paulo, Andrei de Oliveira Almeida, Pedro Machado de Almeida, Pedro Gomes Barbosa
Summary: This work proposes a control strategy for integrating an offshore wind farm into the onshore electrical grid using a high-voltage dc transmission system based on modular multilevel converters. The algorithm allows the system to operate in grid-connected or stand-alone modes, with the second case supplying power to local loads. Mathematical models were developed for each operation mode and used to design the converter's controllers. The proposed control strategy was tested under different scenarios and demonstrated satisfactory performance.
Article
Engineering, Electrical & Electronic
Pengfei Hu, Rui Yin, Baoze Wei, Yongjie Luo, Frede Blaabjerg
Summary: This letter proposes a novel all dc system for offshore wind farm collection and integration, aiming to increase power density, reduce costs, and improve efficiency. The system consists of medium-voltage dc collection systems and a dc transmission system, with a modular isolated dc/dc converter (MIDC) topology for maximum power point tracking of wind generators. Through simulations and experiments, the feasibility of the proposed pure dc system is verified.
IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS
(2021)
Article
Energy & Fuels
Zheren Zhang, Yingjie Tang, Zheng Xu
Summary: The paper proposes a medium-frequency wind farm and MMC-HVDC integration system, which increases the offshore system operating frequency to reduce the actual value of electrical equipment and minimize platform space requirements. Time domain simulation results demonstrate that the dynamic behavior of the system is not significantly affected by the increase in offshore AC system frequency in most scenarios.
Article
Engineering, Electrical & Electronic
Ramin Razani, Yasser Abdel-Rady I. Mohamed
Summary: This study investigates the operation limits of a hybrid dc/dc modular multilevel converter, identifying minimum achievable ac circulating current and maximum transmitted power impacted by unbalance in capacitor voltages. The research reveals that hybrid converters with larger transmitted power, higher conversion ratios, and larger arm inductance have more limited operation ranges.
IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Haiyu Zhao, Hongyu Zhou, Wei Yao, Qihang Zong, Jinyu Wen
Summary: In this paper, a Multi-stage Sequential Network Energy Control (MSNEC) is proposed for offshore AC asymmetric fault ride-through. Simulation results verify the effectiveness and economy of the proposed method.
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
(2023)
Article
Engineering, Chemical
Muhammad Shoaib Bhutta, Tang Xuebang, Muhammad Faheem, Fahad M. Almasoudi, Khaled Saleem S. Alatawi, Huali Guo
Summary: The lack of synchronization between offshore wind farms (OWFs) and onshore grids in high voltage DC systems is caused by the stochastic nature of wind energy, resulting in various system disturbances, grid contingencies, power loss, and frequency instability. This research focuses on frequency stability analysis and proposes a dynamic coordination control technique for a Double Fed Induction Generator (DFIG) integrated with a hybrid multi-terminal HVDC (MTDC) system consisting of OWFs. Line commutated converters (LCC) and voltage source converters (VSC) are utilized in the suggested control method to ensure frequency stability. An adaptive neuro-fuzzy inference approach is employed for accurate wind speed prediction to further enhance frequency stability. The proposed HVDC system can integrate multiple distributed OWFs with the onshore grid system, and the control strategy is designed based on this concept. To ensure the transient stability of the HVDC system, the DFIG-based OWF is regulated by a rotor side controller (RSC) and a grid side controller (GSC) at the grid side using STATCOM. The performance of the devised HVDC (MTDC) is evaluated in MATLAB/SIMULINK by considering different parameters such as frequency, wind power, rotor and stator side current, torque, speed, and power, and the experimental results are compared with a conventional optimal power flow (OPF) model to validate the performance.
Article
Energy & Fuels
Harith R. Wickramasinghe, Pingyang Sun, Georgios Konstantinou
Summary: This study demonstrates the interoperability of an emerging alternate arm converter (AAC) with the state-of-the-art modular multilevel converter (MMC) in high-voltage direct current (HVDC) systems based on a hybrid VSC-HVDC system. Through detailed analysis of an 800 MVA hybrid voltage source converter (VSC)-HVDC system, the study showcases the interoperability performance of the AAC under different operating scenarios and verifies its associated control functions.
Article
Engineering, Electrical & Electronic
Bin Xu, Chong Gao, Jing Zhang, Jun Yang, Bing Xia, Zhiyuan He
Summary: The article discusses the use of dc choppers in offshore wind power links to prevent equipment damage from sudden increases in dc-link voltage. A novel dc chopper topology with both centralized and distributed resistances is proposed, offering flexibility to balance pros and cons of existing topologies. The new topology achieves great electromagnetic interference performance, precise power control, and reduced system disturbance.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Automation & Control Systems
Md. Ashib Rahman, Md. Rabiul Islam, Kashem M. Muttaqi, Danny Sutanto
Summary: This article proposes a modular magnetic linked converter station (CS) for offshore power transfer through a high voltage dc (HVDC) link. The proposed converter station can collect both medium voltage ac and dc power simultaneously and transform them to HVDC suitable for offshore power transmission. The converter station incorporates multiple half-bridge (HB) converters as a front-end interface for power collection, and high-frequency magnetic linked multiport converters (MLMCs) for voltage isolation and step-up. The simulation study and laboratory scale experiment demonstrate the satisfactory performance of the proposed CS with the proposed controller.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2023)
Article
Green & Sustainable Science & Technology
Yingjie Tang, Zheren Zhang, Zheng Xu
Summary: The article introduces a competitive solution for offshore wind farm integration using LFAC technology, with a hybrid onshore BtB converter system and corresponding control strategies proposed. The feasibility of the scheme is verified through calculated eigenvalues and time-domain simulations.
IEEE TRANSACTIONS ON SUSTAINABLE ENERGY
(2021)
Article
Energy & Fuels
Kai Huang, Lie Xu, Guangchen Liu
Summary: The proposed DR-MMC Hub integrates offshore wind power to the onshore DC network and offshore production platforms with different DC voltage levels. Compared to conventional parallel-connected DR-MMC HVDC systems, the DR-MMC hub reduces the required MMC converter rating, leading to lower investment cost and power loss. System control considers different control modes and behaviors during AC and DC faults are investigated, using hybrid MMCs for safe operation. Simulation results validate the operation of the DR-MMC hub.
Article
Engineering, Electrical & Electronic
Xiangjie Xie, Hui Li, Hongtao Tan, Ran Yao, Jie Zheng
Summary: This paper proposes a fault-tolerant strategy for offshore DC wind turbines, utilizing a direct-drive permanent magnet synchronous generator and a modular multilevel converter. The strategy is immune to variable operation conditions and the injection of second-order harmonic circulating current. It requires no additional sensors or estimators and is proven to be effective through simulation and experimental results.
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
(2023)
Article
Green & Sustainable Science & Technology
Sihang Wu, Xiangyu Zhang, Wenxuan Jia, Yuan Zhu, Lei Qi, Xiaojiang Guo, Xiaofeng Pan
Summary: This paper proposes a modular multilevel converter with integrated energy dissipation equipment to meet the requirement of fault ride through and provide an economic and reliable solution.
IEEE TRANSACTIONS ON SUSTAINABLE ENERGY
(2022)
Article
Energy & Fuels
Matthias Quester, Fisnik Loku, Otmane El Azzati, Leonel Noris, Yongtao Yang, Albert Moser
Summary: Offshore wind farms in the North Sea are increasingly connected to the onshore AC transmission systems using HVDC systems. The converters and control systems used in wind farms can lead to stability problems, which can be predicted using impedance-based analysis. An enhanced impedance measurement method is proposed in this paper to assess the converter-driven stability of offshore HVDC systems, with results showing potential interactions between onshore converters and AC grids.
Article
Automation & Control Systems
Wu Zeng, Rui Li, Lei Huang, Chang Liu, Xu Cai
Summary: This article investigates the impact of grid connection of offshore wind farms through MMC-HVdc transmission system on low inertia issue and proposes a method to compensate for the inertia by integrating UESS into MMC.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2022)
Article
Energy & Fuels
Abeba Debru, Mulu Bayray, Marta Molinas
Summary: The performance of the Adama-II Wind Farm was assessed in comparison to a feasibility study, showing significant deviations in wind speed, power density, and wind directions. The Capacity factor, Annual Energy Production (AEP), and Availability of wind turbines were also analyzed, with deviations attributed to differences in long-term correction data and weather conditions during the study period.
Article
Automation & Control Systems
Bing Tian, Marta Molinas, Quntao An, Bo Zhou, Jiadan Wei
Summary: This article presents a new design approach for sensorless FOC by utilizing the freewheeling current to enhance the fault-tolerant capability of electric drives. The mathematical model of the freewheeling current is established, and a second-order generalized integrator with a frequency-locked loop is used to extract position/speed estimates. Experimental results validate the effectiveness of the proposed approach.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2022)
Article
Engineering, Electrical & Electronic
Haoxiang Zong, Chen Zhang, Xu Cai, Marta Molinas
Summary: This paper focuses on the analysis of oscillation propagation in hybrid AC/DC grids. The mechanism of oscillation propagation and its characteristics are analyzed, and a systematic method for propagation analysis is presented. Finally, case studies are conducted to validate the analysis.
IEEE TRANSACTIONS ON POWER SYSTEMS
(2022)
Article
Energy & Fuels
Yu Zhang, Chen Zhang, Renxin Yang, Marta Molinas, Xu Cai
Summary: The necessity of limiting the output current of Gridforming Voltage Source Converter has resulted in significant deformation of its Power Angle Characteristic, which poses a major challenge to the analysis of Transient Synchronization Stability.
IEEE TRANSACTIONS ON ENERGY CONVERSION
(2023)
Article
Engineering, Electrical & Electronic
Chen Zhang, Haoxiang Zong, Xu Cai, Marta Molinas
Summary: Frequency-Domain (FD) modal method is a useful tool for oscillation analysis of converters-dominated systems. In this letter, the mathematical relation between the nodal admittance and loop-gain models and their respective eigen-sensitivity-based Participation Factor (PF) analysis methods is established. The validity of this relation is validated through numeric case studies of a converters-interlinked system. Furthermore, discussions on the TD/FD eigen-sensitivity are also helpful for the promotion of modal methods, such as facilitating cross-domain modal analysis.
IEEE TRANSACTIONS ON POWER SYSTEMS
(2023)
Article
Engineering, Electrical & Electronic
Raju Wagle, Pawan Sharma, Charu Sharma, Mohammad Amin, Jose Luis Rueda, Francisco Gonzalez-Longatt
Summary: Future distribution networks face challenges such as rapid load changes and high penetration of variable distributed energy resources. This paper proposes an optimal power flow-based reactive power control method using smart converters to address voltage violations. It utilizes the latest information communication technology of smart converters and real-time monitoring and control through cyber-physical co-simulation.
IET GENERATION TRANSMISSION & DISTRIBUTION
(2023)
Article
Thermodynamics
Raju Wagle, Pawan Sharma, Charu Sharma, Mohammad Amin
Summary: This paper proposes an optimal power flow (OPF)-based control method for smart inverters (SI), aiming to address voltage violations in distribution networks with a higher penetration of inverter-based generations. By optimizing the power flow, more accurate operating set points can be obtained to regulate the voltage at affected nodes. Compared with sensitivity-based Volt-Var Control (VVC), Volt-Watt Control (VWC), and combined VVC and VWC methods, the proposed OPF-based control optimizes network loss and maintains voltage violations with less reactive power support in a European low-voltage and CIGRE medium-voltage distribution network.
INTERNATIONAL JOURNAL OF GREEN ENERGY
(2023)
Article
Engineering, Electrical & Electronic
Bing Tian, Runze Lu, Jiadan Wei, Marta Molinas, Kai Wang, Zhuoran Zhang
Summary: This study focuses on two-phase insulation faults in five-phase permanent magnet synchronous motors. It proposes a general method to handle neutral voltage issues and establishes a comprehensive faulty motor model. It also presents a revised phase-voltage modulation method that is independent of fault severity. Experimental results confirm the effectiveness of the proposed method under various fault conditions.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2023)
Article
Engineering, Electrical & Electronic
Sjur Foyen, Chen Zhang, Yu Zhang, Takanori Isobe, Olav Bjarte Fosso, Xu Cai, Marta Molinas
Summary: The chirp sweep is a fast and simple technique for wide-band impedance measurement. However, it becomes inaccurate for weakly damped systems with frequency couplings. This paper proposes a multiple chirp reference frame filter observer to estimate real-time harmonic transfer functions and their associated chirp errors, effectively controlling the errors to negligible values. Experimental results on a single-phase STATCOM support the effectiveness of the proposed approach for weakly damped and frequency coupled systems.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2023)
Article
Engineering, Electrical & Electronic
Kazuki Ohuchi, Yuko Hirase, Marta Molinas
Summary: This study focuses on the impact of grid-connected inverters with virtual synchronous generator (VSG) control on stability in large, complex systems. The results show that VSG controls may resonate with output filters in the kHz band and capacitance in long transmission lines can cause system instability.
IEEJ JOURNAL OF INDUSTRY APPLICATIONS
(2023)
Article
Engineering, Biomedical
Majid Aljalal, Marta Molinas, Saeed A. Aldosari, Khalil AlSharabi, Akram M. Abdurraqeeb, Fahd A. Alturki
Summary: This study explores the use of electroencephalography (EEG) to detect mild cognitive impairment (MCI). Researchers decompose the EEG signals using variational mode decomposition (VMD) and extract features using entropy measures. Several machine learning techniques are used for classification, and the results show that selecting a few suitable EEG channels can achieve high accuracy. This research paves the way for accurately diagnosing this brain disorder using a minimal number of electrodes.
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
(2024)
Proceedings Paper
Energy & Fuels
Haoxiang Zong, Chen Zhang, Xu Cai, Marta Molinas
Summary: This paper establishes a frequency-domain network model for assessing oscillations in hybrid AC/DC grids and provides a foundation for data-driven oscillation diagnosis.
2022 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-HIMEJI 2022- ECCE ASIA)
(2022)
Proceedings Paper
Energy & Fuels
Kazuki Ohuchi, Yuko Hirase, Marta Molinas
Summary: This study analyzes the dynamic characteristics of a large-scale power system with the introduction of a large number of DGs with advanced inverter controls through impedance-based analysis. It also investigates the effect of the capacitance of passive filters and transmission lines in advanced DGs on stability.
2022 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-HIMEJI 2022- ECCE ASIA)
(2022)
Proceedings Paper
Energy & Fuels
Sjur Foyen, Chen Zhang, Marta Molinas, Olav Fossol, Takanori Isobe
Summary: In this paper, we developed a model using chirp excitation signals, which takes advantage of their time-frequency properties to provide impedance frequency response for single-phase AC-DC converters. The developed model can also be applied to other linear time-periodic and linear time-invariant systems.
2022 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-HIMEJI 2022- ECCE ASIA)
(2022)
Article
Engineering, Electrical & Electronic
Yu Wang, Yuanpeng Guan, Olav Fosso, Marta Molinas, Si-Zhe Chen, Yun Zhang
Summary: A triple-close-loop input-voltage-sharing (IVS) strategy is proposed in this article to improve the stability and dynamic performance of the ISOP structure IBdc by reshaping the input impedance.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2022)
