Tapping Existing LCC-HVdc Systems with Voltage Source Converters

This paper presents the application of a Full-bridge modular multi-level converter (FB-MMC) to tap an existing LCC-HVdc system. During faults, the dc voltage of the FB-MMC is controlled to reduce the fault current instead of blocking the converters. Electromagnetic Transient Simulations performed with PSCAD has been used to demonstrate the performance of the proposed system. Control strategies have been proposed in case of ac and dc faults at the three terminals. The results presented in this paper clearly indicate the benefits of using a FB-MMC with a controlled fault clearing strategy to tap an existing LCC-HVdc system.