Low-Voltage-Ride-Through (LVRT) Control of an HVDC Transmission System Using Two Modular Multilevel DSCC Converters

This paper presents an intensive discussion on a high-voltage direct-current (HVDC) long-distance transmission system combining two modular multilevel double-star chopper-cells (DSCC) converters with dc power cables. Hereinafter, each converter is referred to simply as a DSCC converter, or just as a DSCC for more simplicity. Such an HVDC transmission system is required to provide low-voltage-ride-through (LVRT) capability to enhance system availability. This paper proposes a practical LVRT control characterized by the use of power-line communications between the two DSCC converters. The validity and effectiveness of the LVRT control is verified not only by simulated waveforms obtained from the software package PSCAD/EMTDC but also by experimental waveforms from a three-phase 200-V, 400-Vdc, 10-kW, 50-Hz downscaled system with 300-m-long dc power cables.