627 / 2019-04-04 09:05:29

Fault line identification method for multi-terminal hybrid DC transmission system

Wudongde three-end hybrid DC; confluence area; fault line identification; wavelet transform; Medium and low band energy

To deal with the problem that the different lines of the multi-terminal hybrid DC system are directly connected and cannot rely on the characteristics of the DC line boundary for fault identification, the Wudongde three-terminal hybrid DC demonstration project is used as the background to study the confluence area of the three-terminal star-type HVDC transmission system. According to Peterson's law and superposition theorem, the variation characteristics of transient current traveling wave on both sides of the confluence region after fault are obtained. It is found that the current traveling wave passes through the confluence region and has a large attenuation in the middle and low frequency bands. Therefore, the wavelet transform is used to extract the low-frequency energy of the fault current traveling wave on both sides of the confluence region, and the fault identification criterion is constructed according to the standard deviation of the two-side wavelet energy, so that the fault line can be identified quickly and reliably. Finally, based on the simulation results, the correctness of the fault identification method is verified.