An Improved Distance Protection Method For Positive Sequence Voltage Polarization Based On Offset Angle

Power electronic converters are used at both ends of 220 kV alternating current (AC) lines in offshore wind farms, and their fault characteristics are greatly affected by the converters, and there is a risk of incorrect action when traditional distance protection is applied to AC lines of flexible direct current (DC) delivery systems. To address this problem, the low voltage ride-through control strategy of the grid-side converter is introduced, and its influence on the action characteristics of distance protection based on positive sequence voltage polarization is analyzed. On this basis, an improved distance protection method is proposed to adjust the distance protection action range by using the offset angle to ensure the correct action of the distance protection, and the effectiveness of the proposed method is verified by the PSCAD/EMTDC simulation test results.