| 1. |
- Duan, Jinpei, et al.
(author)
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Dual-Circulant Modulation for Modular Multilevel DC/DC Converters With Inherent Balance Capability
- 2023
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In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 38:7, s. 7958-7963
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Journal article (peer-reviewed)abstract
- Modular multilevel dc/dc converters (MMDC) have emerged recently for medium-voltage dc applications. Under single-circulant modulation, the submodule (SM) capacitor voltages in MMDC are found to be evenly divided only at some specific modulation coefficients. To obtain the inherent balance capability under all modulation coefficients and expand the application range of circulant modulation, a simple dual-circulant modulation is proposed in this letter. On the basis of single-circulant modulation, the self-balancing of the SM capacitor voltages is realized by using the additional switching patterns generated by a simple circulant permutation method. The theoretical analysis of the proposed method is presented, and the inherent balance capability of MMDC under the dual-circulant modulation method is verified by experiments.
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| 2. |
- Ojo, Olorunfemi, et al.
(author)
-
Welcome From: Technical Program Chairs
- 2023
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In: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Conference paper (peer-reviewed)
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| 3. |
- Wang, Xinshuo, et al.
(author)
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Transient Overvoltage Analysis of Grid-Following VSCs during Fault Recovery
- 2023
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In: ICPE 2023-ECCE Asia. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 2404-2409
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Conference paper (peer-reviewed)abstract
- Current grid code has explicit requirement on the fault current injection profile of grid-following voltage-source converters (GFL-VSCs), i.e., the output reactive current of GFL-VSC needs to be proportional to voltage- magnitude deviation at the point of connection (PoC) until its current limitation is reached. This article points out that such way of injecting the fault current may result in transient overvoltage (TOV) at the PoC during fault recovery, and the rate of change of current reference of GFL-VSC is critical to the duration of TOV. Moreover, a method for estimating the maximum magnitude of TOV is presented, which provides an intuitive insight for the TOV phenomenon.
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| 4. |
- Wang, Zhihao, et al.
(author)
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Current Reference Control Scheme of Voltage Source Converters to Ensure the Existence of Stable Equilibrium Points During Grid Fault
- 2023
-
In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 38:9, s. 10750-10765
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Journal article (peer-reviewed)abstract
- Maintaining synchronization with the grid during fault ride-through (FRT) is essential for grid-connected voltage source converters (VSCs). However, improper current references can lead to a loss of synchronization during FRT due to the nonexistence of stable equilibrium points (SEPs). While the mechanism of SEPs has been explained, the development of control schemes ensuring their existence remains challenging due to the difficulty of obtaining real-time grid parameters during FRT. To address this issue, this article proposes a novel current reference control scheme that only requires prefault grid parameters. By analyzing the changes in grid parameters caused by faults and characterizing the correspondence between the during-fault and prefault grid parameters, a voltage-dependent current reference control scheme is proposed. Since no real-time grid parameter estimation is needed during FRT, the proposed control scheme is practical and easy to implement. Simulation studies using DIgSILENT PowerFactory demonstrate that the proposed control scheme enables the VSC to maintain synchronization with the grid under the conditions of short-circuit ratio equaling 1.3 and grid voltage dropping to 0.1 p.u. Moreover, experiments further verify the effectiveness and feasibility of the proposed control scheme.
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| 5. |
- Zhan, Changjiang, et al.
(author)
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An Overview of Stability Studies of Grid-forming Voltage Source Converters
- 2023
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In: Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering. - : Chinese Society for Electrical Engineering. - 0258-8013. ; 43:6, s. 2339-2358
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Journal article (peer-reviewed)abstract
- Unlike grid-following converters, the grid-forming converter is operated as a synchronous voltage source, which can effectively improve the stability of power-electronics-dominated power systems, and hence, has attracted much research attention in recent years. As a basis of the large-scale implementation of grid-forming converters, there should be an in-depth understanding of its stability under different grid strengths as well as different grid disturbances. This article performs a comprehensive overview of the stability studies of grid-forming converters from the perspective of existence of equilibrium points, small-signal stability, and transient stability. On top of this, stabilization control solutions of grid-forming converters are also summarized. In the end, perspectives on the prospects and challenges of stability analysis of grid-forming converters are shared.
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| 6. |
- Bhadoria, Shubhangi, et al.
(author)
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Enablers for Overcurrent Capability of Silicon-Carbide-Based Power Converters : An Overview
- 2023
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In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 0885-8993 .- 1941-0107. ; 38:3, s. 3569-3589
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Journal article (peer-reviewed)abstract
- With the increase in penetration of power electronic converters in the power systems, a demand for overcurrent/ overloading capability has risen for the fault clearance duration. This article gives an overview of the limiting factors and the recent technologies for the overcurrent performance of SiC power modules in power electronics converters. It presents the limitations produced at the power module level by packaging materials, which include semiconductor chips, substrates, metallization, bonding techniques, die attach, and encapsulation materials. Specifically, technologies for overcurrent related temperatures in excess of 200°C are discussed. This article also discusses potential technologies, which have been proven or may be potential candidates for improving the safe operating area. The discussed technologies are use of phase-change materials below the semiconductor chip, Peltier elements, new layouts of the power modules, control and modulation techniques for converters. Special attention has been given to an overview of various potential phase-change materials, which can be considered for high-temperature operations.
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| 7. |
- Chen, Feifan, et al.
(author)
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Dynamics Enhancement for Power Synchronization Control with Asymmetric AC Voltage Controller in Strong Grids
- 2023
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In: 2023 IEEE Conference on Control Technology and Applications, CCTA 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1066-1070
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Conference paper (peer-reviewed)abstract
- Power synchronization control (PSC) is designed for weak grid connections originally and its performance is weakened when connected to a strong grid. In this paper, an asymmetric AC voltage controller (AVC) is proposed to improve the performance of PSC in strong grids. The improvement is achieved by adding a coupling from d-axis to q-axis to the voltage control part. The effect of this d-to-q coupling is explained by small signal modeling. It is found that the asymmetric AVC gives an effective improvement in damping the low-frequency oscillation and stability robustness against the grid strengths. Theoretical analysis and experiments verify the effectiveness of the proposed asymmetric AVC.
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| 8. |
- Chen, Feifan, et al.
(author)
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Pitfalls of Using Passivity Index to Guide Grid-connected Inverter Control Design in Low-frequency Region
- 2023
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In: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 758-764
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Conference paper (peer-reviewed)abstract
- The main purpose of this article is to elaborate on the pitfalls of using the frequency-domain passivity theories in grid-inverter interactions within the low-frequency range. It mainly covers the relationship between the passivity index and stability, considerations for control design guided by optimizing the passivity index, and issues with a negative infinite index. It is advised to exercise caution when applying passivity theory in the low-frequency range. These conclusions have been substantiated through numerical and experimental studies.
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| 9. |
- Cheng, Li, et al.
(author)
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Neural-Network-Based Impedance Estimation for Transmission Cables Considering Aging Effect
- 2023
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In: 2023 8th IEEE Workshop on the Electronic Grid, eGRID 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- In power-electronic-based power systems like wind farms, conducting stability analysis necessitates a comprehensive understanding of the system impedance across a wide frequency range, from sub-harmonic frequencies up to the Nyquist frequency of control systems of power converters. The cable aging effect can significantly impact the cable impedance, while accurately estimating the degree of aging proves challenging. To avoid the requirement for precise aging prognostic, this paper proposes an approach based on Artificial Neural Networks (ANN) that enables the estimation of AC cable impedance in a wind farm solely through fundamental frequency measurements. The data used for training the ANN is obtained from the cable model in PSCAD, incorporating physical and geometrical parameters, which accurately approximates real cables within power systems. The training results of the ANN validate the accuracy of the proposed identification approach. As a result, the proposed approach effectively eliminates the potential misjudgment of system stability caused by the aging effect of power cables.
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| 10. |
- Cheng, Li, et al.
(author)
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Online Identification of Wind Farm Wide Frequency Admittance with Power Cables Using the Artificial Neural Network
- 2023
-
In: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1530-1535
-
Conference paper (peer-reviewed)abstract
- In power-electronic-based power systems like wind farms, stability analysis requires knowledge of system impedance across a wide frequency range, from sub-harmonic frequencies to the Nyquist frequency. Although it is feasible to take the fundamental frequency measurement during power system operation, obtaining a wide-frequency impedance curve in real time is very challenging. This paper proposed an ANN-based approach to estimate wide-frequency system admittance of wind farms with power cables, through fundamental frequency measurements. Real-life uncertainties are considered, including shunt capacitor injection, filter inductance variance, cable aging, errors in voltage and current measurements, and the variance of other system parameters. The generalization ability of the ANN is validated on a new dataset with different uncertainty distributions, and the error sensitivity to the potential system parameter variance is evaluated. These results can be referenced in the data acquisition step in future neural-network-based applications.
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