Feasibility and Reliability Analysis of LCC DC Grids and LCC/VSC Hybrid DC Grids

Li, Gen; Liang, Jun; Joseph, Tibin; An, Ting; Lu, Jingjing; Szechtman, M.; Andersen, Bjarne R.; Zhuang, Qikai

doi:10.1109/access.2019.2898387

Cited by 68 publications

(41 citation statements)

References 35 publications

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“…Line-Commutated Converter based HVDC (LCC-HVDC) technology has been extensively utilized around the world for long-distance bulk-power transmission due to its merits such as the thyristor's superior power handling capability and lower operating power losses [1], [2]. Nevertheless, the development of LCC-HVDC systems suffers from some wellknown challenges such as poor voltage regulation ability and vulnerability to commutation failures during inverter ac fault incidents, which can lead to a temporary cessation of transmitted power, overheating of the valves, and misoperation of the protective relays [3].…”

Section: Introductionmentioning

confidence: 99%

A Controllable Thyristor-Based Commutation Failure Inhibitor for LCC-HVDC Transmission Systems

Mirsaeidi

Tzelepis

et al. 2021

IEEE Trans. Power Electron.

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Commutation failure is a serious malfunction in linecommutated High Voltage Direct Current (HVDC) converters which is mainly caused by the inverter ac faults, and results in a temporary interruption of transmitted power and damage to the converter equipment. In this paper, a Controllable Commutation Failure Inhibitor (CCFI) is developed which obviates the main drawbacks of the existing power-electronic-based and faultcurrent-limiting-based strategies. Under normal circumstances, the developed CCFI improves the steady-state stability and the power transfer capability of the inverter ac lines, while it does not cause excessive voltage stress on the converter valves. In addition, it would reduce the risk of commutation failure occurrence, since it does not lead to any voltage drop in the commutation circuit. When a fault occurs at one of the inverter ac systems, its corresponding CCFI limits the fault current depending on the reduced extinction angle. This would not only inhibit the successive commutation failures on the HVDC converter, but also extend the lifetime of components in the inverter ac systems. The practical feasibility of the developed CCFI is assessed through laboratory testing, using real-time Opal-RT hardware prototyping platform. The obtained results indicate that the developed CCFI can reliably inhibit the commutation failures during various types of faults.

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Section: Introductionmentioning

confidence: 99%

A Controllable Thyristor-Based Commutation Failure Inhibitor for LCC-HVDC Transmission Systems

Mirsaeidi

Tzelepis

et al. 2021

IEEE Trans. Power Electron.

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“…N recent years, the voltage source converter (VSC) based high-voltage direct-current (HVDC) technology, especially the modular multilevel converter (MMC) based HVDC, has attracted considerably more attention for renewable energy integration and multi-terminal applications compared to line commutated converter (LCC) based HVDC [1]- [3]. Thanks to their distinctive features, such as the modularity and scalability to different voltage/power levels, high efficiency, and superior harmonic performance [4]- [6], the MMC-HVDC technology has been planned for systems of high capacity and high dc voltage level. Examples include the Zhangbei four-terminal ±500 kV HVDC grid [7] and the Kun-Liu-Long three-terminal ±800 kV hybrid LCC/MMC ultra HVDC project [4].…”

Section: Introductionmentioning

confidence: 99%

“…Thanks to their distinctive features, such as the modularity and scalability to different voltage/power levels, high efficiency, and superior harmonic performance [4]- [6], the MMC-HVDC technology has been planned for systems of high capacity and high dc voltage level. Examples include the Zhangbei four-terminal ±500 kV HVDC grid [7] and the Kun-Liu-Long three-terminal ±800 kV hybrid LCC/MMC ultra HVDC project [4].…”

Section: Introductionmentioning

confidence: 99%

Protection for Submodule Overvoltage Caused by Converter Valve-Side Single-Phase-to-Ground Faults in FB-MMC Based Bipolar HVDC Systems

Liang

Ugalde‐Loo

et al. 2020

IEEE Trans. Power Delivery

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One of the most critical faults affecting modular multilevel converter (MMC) based bipolar high-voltage directcurrent (HVDC) transmission systems is the single-phase-toground (SPG) faults between the converter transformer and the valve. However, half-bridge (HB) and full-bridge (FB) based MMCs exhibit a different behavior following such a fault and, thus, converter protection should be addressed in a different manner for each configuration. For HB-MMCs, an SPG fault at the valve-side leads to a severe overvoltage on the submodule (SM) capacitors in the converter upper arms and to grid-side non-zero crossing currents. Although FB-MMCs only exhibit overvoltage, these are more severe than for their HB counterparts. To address this problem, this paper presents a protection strategy considering thyristor bypass branches placed in parallel with upper arms of FB-MMCs. By employing this configuration, the upper arm overvoltage in the faulted converter is mitigated and remote converters can be quickly blocked using their local protection schemes. For completeness, the effectiveness of the strategy is verified through time-domain simulations in PSCAD/ EMTDC. The studies in this paper demonstrate the effectiveness of the presented protection scheme for station internal faults occurring in FB-MMCs in bipolar HVDC systems.

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“…The voltage source converter (VSC) technology is becoming an attractive alternative to conventional line commutated converters (LCCs) for its features. These include [4]- [5]: 1) compact and flexible station layouts, with low space requirements, and a scalable system design; 2) a high dynamic performance and stable operation with AC networks; 3) capability of supplying power to passive networks and black-start; 4) an independent control of active and reactive power; and 5) no voltage polarity reversal during power flow reversal. Therefore, VSC-based DC systems are more suitable for distributed renewable energy integration than their LCC counterpart.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of MVAC and MVDC Systems in Dynamic Operation, Fault Protection and Post-Fault Restoration

Zhang

Joseph

et al. 2019

IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society

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One of the most significant obstacles preventing the large-scale application of direct-current (DC) technology in medium voltage (MV) distribution networks is their fault protection. The existing AC relay protection needs to be changed or redesigned to protect the future overlay MVAC and MVDC distribution networks. Therefore, a comprehensive understanding of the dynamic and fault behavior and post-fault restoration strategies of MVAC and MVDC systems are critically important. Moreover, a comparison of MVAC and MVDC systems during a fault will also contribute to designing the protection systems of hybrid MV AC/DC systems. In this paper, the challenges of protecting DC faults of MVDC systems and possible solutions are first introduced. Then, the fault characteristics and post-fault restoration of MVDC and MVAC distribution systems are compared and investigated through case studies. Time-domain simulations have been conducted in PSCAD/EMTDC. The work in this paper will be valuable for the protection design for future hybrid MV AC/DC systems.

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Feasibility and Reliability Analysis of LCC DC Grids and LCC/VSC Hybrid DC Grids

Cited by 68 publications

References 35 publications

A Controllable Thyristor-Based Commutation Failure Inhibitor for LCC-HVDC Transmission Systems

A Controllable Thyristor-Based Commutation Failure Inhibitor for LCC-HVDC Transmission Systems

Protection for Submodule Overvoltage Caused by Converter Valve-Side Single-Phase-to-Ground Faults in FB-MMC Based Bipolar HVDC Systems

Comparisons of MVAC and MVDC Systems in Dynamic Operation, Fault Protection and Post-Fault Restoration

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