Impact of Strength and Proximity of Receiving AC Systems on Cascaded LCC-MMC Hybrid HVDC System

He, Yongjie; Xiang, Wang; Ni, Binye; Lu, Xiaojun; Wen, Jinyu

doi:10.1109/tpwrd.2021.3073896

Cited by 19 publications

(5 citation statements)

References 27 publications

(21 reference statements)

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“…The modelling scheme for the SSM can be referred to [25,26], and it is omitted here. It is worth noting that there are two differences between this paper and the aforementioned references: (1) both the rectifier and the inverter adopt the hybrid cascaded structure; (2) both the MMC1 and MMC2 adopt GFM control [21].…”

Section: Figurementioning

confidence: 99%

“…This unique cascaded structure results in a complex coupling effect between them, where currents and voltages mutually influence the internal electrical parameters. In fact, this structure diminishes the stability margin of the HC‐HVDC [26]. Furthermore, the conventional communication‐free frequency support control scheme for HVDC integrated wind farms typically utilizes DC voltage to convey frequency information [27].…”

Section: Introductionmentioning

confidence: 99%

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Frequency support scheme of grid‐forming based hybrid cascaded HVDC integrated wind farms

Fan,

Chi,

Wang

2024

IET Generation Trans & Dist

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The grid‐following control‐based hybrid cascaded high‐voltage direct current (HC‐HVDC) links may contribute to the worsening of inertia decline and instability issues, especially in situations characterized by a weak grid. To address the challenge, this paper proposes a grid‐forming (GFM) based optimal frequency support scheme (OFSS) for HC‐HVDC integrated wind farms. Firstly, a GFM control for hybrid converter is proposed and its stability under weak grid conditions is evaluated through a small‐signal model. Then, DC current–voltage droop control is introduced to the line commutated converter (LCC). This control approach ensures the consistency of reactive power in the LCC by regulating the DC voltage and current in the same direction, thereby mitigating AC voltage fluctuations. It also facilitates active power control in the LCC in response to grid frequency variations. Furthermore, the OFSS can convey the frequency of receiving‐end grid to the rectifier and wind farms without communication for precise power control. Finally, to validate the effectiveness of OFSS, a point‐to‐point HC‐HVDC and a 4‐machine test model are constructed on PSCAD/EMTDC. The OFSS significantly enhances the frequency support capability of HC‐HVDC links and improves the robustness in weak grid.

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Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Frequency support scheme of grid‐forming based hybrid cascaded HVDC integrated wind farms

Fan,

Chi,

Wang

2024

IET Generation Trans & Dist

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“…A coordinated control strategy based on the dynamic limiter, diodes and LCC-MMC active orders is proposed was suggested to improve the AC side voltage stability (Zhao and Tao, 2021). A supplementary coupling mitigation control strategy was suggested to enhance the stability of a hybrid cascaded HVDC system connected to a weak grid (He et al, 2021). A suppression strategy based on fuzzy clustering and an identification method were proposed to repress the DC overcurrent caused by LCC commutation failure at the inverter side (Guo et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Study on the characteristic of the grounding fault on the cascaded midpoint side of the hybrid cascaded HVDC system

et al. 2023

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The hybrid cascaded high-voltage direct current (HVDC) system combines the system support capabilities of the modular multilevel converter (MMC) with the capacity of the line-mutated converter’s (LCC’s) advantage of high-power transmission. The HVDC system is among the key elements of a smart grid where artificial intelligence is applied extensively. However, the characteristics of a grounding fault on the cascaded midpoint side of a hybrid cascaded HVDC system remain unclear. This study analyzes fault characteristics and the impact of faults using analytical methods. First, the topology and basic control strategy are presented. The fault response process is then analyzed by dividing systems into the MMC and LCC parts at the inverter side. A separate theoretical analysis is also conducted. In addition, the impacts of faults on HVDC and alternating current (AC) networks are analyzed. Therefore, even after the HVDC system is disabled, the AC network can supply fault currents using an antiparallel diode. The simulation results show that the proposed analysis method is feasible, and the theoretical analysis is correct. The proposed method can provide a theoretical basis for the selection of equipment for HVDC systems and smart grid construction.

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“…With the development of VSC converter technology, hybrid HVDC transmission technology integrating LCC and VSC converter has attracted extensive attention. The existing literature focuses on the topology of hybrid HVDC transmission systems [9][10][11], control and protection strategies [12][13][14], small−signal stability analysis [15][16][17], experimental platforms [18][19][20], etc. In November 2020, China approved the Baihetan−Jiangsu HVDC project, which adopts hybrid cascade multi−terminal technology for the first time in the world.…”

Section: Introductionmentioning

confidence: 99%

Optimal Current Allocation Strategy for Hybrid Hierarchical HVDC System with Parallel Operation of High-Voltage and Low-Voltage DC Lines

2022

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For long-distance and bulk-power delivery of new energy, high-voltage direct current (HVDC) is a more effective way than high-voltage alternative current (HVAC). In view of the current capacity disparity between line commutated converter (LCC) and voltage source converter (VSC), a hybrid hierarchical HVDC topology with parallel operation of 800 kV and 400 kV DC lines is investigated. The optimal current allocation method for hybrid hierarchical HVDC is proposed distinct from the same rated current command configuration method of high-voltage and low-voltage converters in traditional topology. Considering the transmission loss reduction of the HVDC system, a multi-order fitting function of transmission loss including LCC converter stations, VSC converter stations and DC lines is established. To minimize the transmission loss and the voltage deviation of key DC nodes comprehensively, a multi-objective genetic algorithm and maximum satisfaction method are utilized to obtain the optimal allocation value of rated current command for high-voltage and low-voltage converters. Through the optimization model, an improved constant current controller based on the current allocation strategy is designed. The hybrid hierarchical HVDC system model is built in PSCAD software, and simulation results verify the effectiveness of the proposed topology and optimal current allocation strategy.

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Impact of Strength and Proximity of Receiving AC Systems on Cascaded LCC-MMC Hybrid HVDC System

Cited by 19 publications

References 27 publications

Frequency support scheme of grid‐forming based hybrid cascaded HVDC integrated wind farms

Frequency support scheme of grid‐forming based hybrid cascaded HVDC integrated wind farms

Study on the characteristic of the grounding fault on the cascaded midpoint side of the hybrid cascaded HVDC system

Optimal Current Allocation Strategy for Hybrid Hierarchical HVDC System with Parallel Operation of High-Voltage and Low-Voltage DC Lines

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