Novel adaptive slope criterion of traveling wave protection for MMC-HVDC system based on fault information pre-recognition from traveling wavefront characteristics

MMC-HVDC systems require for protections of high speed. Traditional slope-based travelling wave(TW) protection is fast without dead zone. However, it exhibits deficiency in sensitivity. To solve this problem, one method is to find new fault characteristics. Such protections usually have high sensitivity, however, fail to combine speed and reliability. Another method is to enhance the sensitivity of traditional TW protection with adaptive setting value. The performance of existing adaptive protections is mainly limited by complex or noise-susceptible setting algorithm. To combine speed, reliability and sensitivity, this paper improves the traditional TW slope-based protection with new setting algorithm. The algorithm can pre-recognize the fault condition of the most serious external fault meeting the characteristics of current TW waveform, including fault area and transient resistance. Then select a suitable setting value according to the pre-recognizing result. The algorithm is noise-robust with only linear time complexity. PSCAD simulations and RTDS experiment show that the proposed adaptive method improves the sensitivity of traditional TW protection by 1.181 to 6 times under different noise levels. It can be used under up to 1000 Ω transient resistance and 20 dB noise without maloperation. The proposed protection has high sensitivity, speed and reliability with relative low sampling frequency requirement.