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Current Calculation Method of Short-circuit Fault at DC Side for MMC Based Two-terminal TWBS-HVDC
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School of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China

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This work is supported by National Natural Science Foundation of China (No. 51677023) and National Key R&D Program of China (No. 2016YFB0900903).

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    Abstract:

    The three-wire bipolar structure based high voltage direct current (TWBS-HVDC) transmission system can greatly enhance the transmission capacity of the DC lines, which has become an effective method for converting AC line into DC line and improving line capacity. Aiming at the difference between TWBS-HVDC and bipolar DC system in connection ways, a current calculation method of short-circuit fault at DC side for two-terminal TWBS-HVDC system is proposed. Firstly, the transient equivalent model of TWBS-HVDC system is established based on modular multilevel converter (MMC) based transient equivalent circuit in the stage from different faults at DC side to the operation of DC breakers of lines. The number of independent circuits and the order of dynamic components in the transient equivalent circuit are taken as the standard, all DC faults are classified into three categories, and the state equations of each kind of fault are analyzed and deduced. The analytical expression of fault current is obtained by solving the eigenvalue and eigenvector of coefficient matrix in the state equation. Finally, a two-terminal TWBS-HVDC system simulation model is established in the MATLAB/Simulink digital simulation platform, and the simulation results validate the effectiveness and accuracy of the state equation solution method of short-circuit fault at the DC side of the proposed TWBS-HVDC system, which can provide a scientific basis for the selection of DC breakers and parameter setting of current limiting reactors.

    表 3 Table 3
    图1 TWBS-HVDC结构示意图Fig.1 Schematic diagram of TWBS-HVDC structure
    图2 TWBS-HVDC运行特性Fig.2 Operation characteristics of TWBS-HVDC
    图3 MMC简化暂态等效电路Fig.3 Simplified transient equivalent circuit of MMC
    图4 TWBS-HVDC简化暂态等效电路Fig.4 Simplified transient equivalent circuit of TWBS-HVDC
    图5 双回路类短路故障暂态等效电路Fig.5 Transient equivalent circuit of short-circuit fault with double-circuit type
    图6 三回路类短路故障暂态等效电路Fig.6 Transient equivalent circuit of short-circuit fault with three-circuit type
    图7 多回路类短路故障暂态等效电路Fig.7 Transient equivalent circuit of short-circuit fault with multi-circuit type
    图8 不同故障距离时双回路类故障解析解与仿真解Fig.8 Analytical results and simulation results of double-circuit type fault with different distances
    图9 不同过渡电阻时双回路类故障解析解与仿真解Fig.9 Analytical results and simulation results of double-circuit type fault with different transition resistances
    表 1 TWBS-HVDC直流故障分类Table 1 DC fault classification of TWBS-HVDC
    表 2 直流故障解析值与仿真值误差Table 2 Errors between analytical values and simulation values of DC fault
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LI Guoqing,LIU Xianchao,ZHANG Song,et al.Current Calculation Method of Short-circuit Fault at DC Side for MMC Based Two-terminal TWBS-HVDC[J].Automation of Electric Power Systems,2020,44(5):91-100.DOI:10.7500/AEPS20190601001

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History
  • Received:June 01,2019
  • Revised:October 14,2019
  • Adopted:
  • Online: March 08,2020
  • Published: