Sensitivity Optimization Scheme of AC Line Differential Protection in MMC-HVDC System of Inverter New Energy Station

doi:10.12204/j.issn.1000-7229.2022.01.007

Abstract

Abstract:

In order to reduce the sensitivity of AC line differential protection in flexible DC transmission system of inverter new energy station, an optimization scheme of differential protection based on improved criterion is proposed. Firstly, according to the AC line fault characteristics of the flexible DC transmission system of the inverter new energy station, the adaptability of the AC line differential protection is analyzed. In case of fault in the normal area, the braking component is set to 0 to improve the sensitivity of the protection. When the phase angle difference on both sides exceeds 90°, the current phase angle difference on both sides is added to the criterion to reduce the reduction of sensitivity. Then, compared with the method of directly reducing the braking coefficient, the optimization scheme can take into account the reliability of differential protection by changing parameters, and the optimization scheme is not affected by the strength of the external system of the inverter new energy station. Finally, the 4-terminal flexible DC system model of inverter new energy station connected to Zhangbei is built in PSCAD simulation software, and the simulation verifies the effectiveness of the optimization scheme.

Key words: new energy, VSC-HVDC, differential protection, sensitivity

CLC Number:

TM773

LIU Yimin, WANG Shuyang, LI Bin, WANG Xingguo, ZHENG Shaoming, DONG Peng. Sensitivity Optimization Scheme of AC Line Differential Protection in MMC-HVDC System of Inverter New Energy Station[J]. ELECTRIC POWER CONSTRUCTION, 2022, 43(1): 63-69.

Figures/Tables 8

Fig.1 Topology diagram of flexible DC delivery system of inverter new energy station

Fig.2 Phasor diagram of fault phase current on both sides of line under phase-to-phase fault between A and B

Fig.3 Schematic diagram of simulation model

Fig.4 Currents in phase A on both sides of the line in case of phase-to-phase fault at F2 between A and B

Fig.5 Angle difference of two-end currents in phase A under phase-to-phase fault at F2 between A and B

Fig.6 Three current ratios under phase-to-phase fault at F2 between A and B

Fig.7 Comparison of each component under phase-to-phase fault at F2 between A and B

Table 1 Performances of differential protection under different fault situations in a weak system

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