Power flow modelling to UHVDC line and its hierarchical connection mode

Li, Shenghu; Wu, Zhengyang; Huang, Jiejie

doi:10.1049/iet-gtd.2017.0851

Cited by 16 publications

(17 citation statements)

References 20 publications

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“…the bipolar mode with 100% capacity (s 1 ), 3/4 bipolar mode with 75% capacity (s 2 ), monopolar mode with 50% capacity (s 3 ), 1/2 bipolar mode with 2 × 25% capacity (s 4 ), 1/2 monopolar mode with 25% capacity (s 5 ), and bipolar outage (s 6 ). For the 3/4 bipolar mode (unbalanced operation mode), owing to different numbers of the converters in the operation of the two poles, the DC variables of the positive and negative poles should be set separately, yielding different equivalent power, and mismatch equations in the power flow model [12], thus need to be differentiated in the OPF.…”

Section: Opf Model Of Ac/uhvdc Systemsmentioning

confidence: 99%

“…However, compared with the high-voltage DC (HVDC) line, at one converter station (CS), the conversion units (CUs) of the UHVDC line are doubled and controlled independently, yielding the unbalanced operation modes, i.e. the 3/4 bipolar mode [12]. The DC variables of the positive and negative poles should be set separately, causing different equality and inequality constraints, thus need to be differentiated in the optimal power flow (OPF) model.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity‐based optimal reliability design of AC/UHVDC systems

Zhang

et al. 2019

IET Generation, Transmission & Distribution

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Section: Opf Model Of Ac/uhvdc Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sensitivity‐based optimal reliability design of AC/UHVDC systems

Zhang

et al. 2019

IET Generation, Transmission & Distribution

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“…However, since there are already many LCC-HVDC projects commissioned in the load centers, the above approach still cannot overcome the instability problem in the receiving power grids, especially when the receiving grid is subject to large disturbances, such as converter blocking [12]. Thus, many efforts have been made towards optimizing the structure of receiving power grids [12]- [17]. References [12]- [15] divide a large-scale synchronous AC network into two asynchronous sub-grids via back-to-back HVDC links, which optimizes the receiving system and effectively enhances the frequency stability.…”

Section: Introductionmentioning

confidence: 99%

A Cascaded Converter Interfacing Long-Distance HVdc and Back-to-Back HVdc Systems

Xiang

Ren-gang

Chang

et al. 2020

IEEE J. Emerg. Sel. Topics Power Electron.

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Abstract-This paper proposes a cascaded converter dedicated to long-distance HVDC infeed and asynchronous back-to-back interconnection of receiving grids. The cascaded converter is consisted of MMCs in series and parallel connection, meeting the high DC voltage and power demand of HVDC system. It realizes hierarchical feeding and asynchronous interconnection of receiving grids, optimizing the multi-infeed short circuit ratio and improving the flexibility of the receiving grids. The topology and operating characteristics of the cascaded converter are introduced in detail. The multi-infeed short-circuits ratio (MISCR) and the maximum power infeed of the cascaded converter based HVDC systems are analyzed. Various feasible operating modes with online switching strategies of the cascaded converter are studied to improve the operational flexibility of the system. The simulation results verify the effectiveness of the control strategy of the HVDC system embedding the cascaded converter. The DC faults clearing strategy and operating modes switching strategies are also validated.

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“…The power stability of UHVDC-HCS is analyzed in [1]. The power flow modeling of an LCC-based UHVDC transmission system hierarchically embedded to an AC grid is presented in [4]. However, there is no such work that deals with impact of static synchronous compensators (STATCOMs) on the operating characteristic of UHVDC-HCS systems.…”

Section: Introductionmentioning

confidence: 99%

Coordinated Control for Operating Characteristics Improvement of UHVDC Transmission Systems under Hierarchical Connection Scheme with STATCOM

2019

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Ultra-high voltage direct current (UHVDC) systems under hierarchical connection schemes (HCSs) linked to AC grids with different voltage levels (500 and 1000 kV) have been a great concern for power utilities to transfer bulk power. They have some operating issues like cascaded commutation failures and longer fault recovery time under certain fault conditions. Since STATCOM has the ability to effectively regulate AC busbar voltages, thus it is considered in this paper to improve the operating characteristics of UHVDC-HCS systems. To further improve the operating characteristics, a coordinated control between an UHVDC-HCS system and STATCOM is presented. To validate the effectiveness of coordinated control, the comparison between different control modes such as reactive power control (Q-control) and voltage control (V-control) in the outer loop control of STATCOM are conducted in detail. Various indices like commutation failure immunity index (CFII) and commutation failure probability index (CFPI) are also comprehensively evaluated in order to investigate robustness of the adopted coordinated control. An UHVDC-HCS system with multiple STATCOMs on the inverter side (500 kV bus) is developed in PSCAD/EMTDC. The impact of coordinated control on commutation failure phenomena and fault recovery time during single and three phase AC faults is analyzed. The analysis shows that coordinated control with V-control mode of STATCOM exhibits better performance in enhancing the operating characteristics of UHVDC-HCS system by improving the CFII, effectively reducing the CFPI and fault recovery time under various AC faults.

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Power flow modelling to UHVDC line and its hierarchical connection mode

Cited by 16 publications

References 20 publications

Sensitivity‐based optimal reliability design of AC/UHVDC systems

Sensitivity‐based optimal reliability design of AC/UHVDC systems

A Cascaded Converter Interfacing Long-Distance HVdc and Back-to-Back HVdc Systems

Coordinated Control for Operating Characteristics Improvement of UHVDC Transmission Systems under Hierarchical Connection Scheme with STATCOM

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