Modeling And Simulation Of MMC-HVDC System Based On RTDS

In recent years, with the development of the wind power and solar power and other renewable power generation, modular multilevel converter (MMC) based HVDC transmission, due to its advantages of flexible, high controllable and switch frequency, becomes the focus of the study.This paper mainly researches on the modeling and simulation of MMC-HVDC system based on RTDS. Sub-module is an important component for MMC, and it has an important effect on the reliability of DC system. Therefore, the sub-module fault characteristic and its redundancy protection strategy are of great significance. As the existing MMC component in RTDS cannot be used in researching sub-module fault characteristics, a defined MMC sub-module is developed in this paper in RTDS/CBuilder programming environment. The proposed sub-module not only occupies small simulation resources, but also can be used to study MMC-HVDC system sub-module fault characteristics and redundancy protection strategy. Furthermore, a new redundancy protection strategy based on carrier phase-shifted modulation is proposed in this paper. The strategy can ensure the converter operate successfully. Moreover, it will not cause DC side voltage obvious fluctuation, and it has little disturbance to system. In order to validate the effective of defined sub-module and redundancy protection strategy, a7-level two terminals MMC-HVDC system is built in RTDS and PSCAD. The simulation results show that the developed sub-module not only occupies small simulation resources, but also can correctly reflect fault characteristic, and the proposed redundancy protection strategy is effectiveness.