A Fault Detection Method for MMC-HVDC Grid Based on Transient Energy of DC Inductor and Submodule Capacitors

The DC fault protection is a key technology for the development of modular multilevel converter based high voltage direct current (MMC-HVDC) grid. Few of the existing fault detection methods are suitable for MMC-HVDC Grid, and the problems such as difficulty in threshold setting and high requirements on hardware are also not neglectable. In this paper, a fault detection method based on transient energy is proposed, in which the characteristics of the transient energy of capacitance of submodules and DC inductance of one converter station are used to set the DC short circuit fault detection criterion. By the proposed method, DC fault detection and fault location can be realized in a short time, and the detection threshold values are easy to set. Besides, the proposed method has a strong immunity to disturbances such as lightning strikes. Simulation results for a four-terminal MMC-HVDC Grid through PSCAD/EMTDC verify the effectiveness of the proposed method.