Simulation of Transients for VSC-HVDC Transmission Systems Based on Modular Multilevel Converters

The development of controllable semiconductor switches and voltage source converter (VSC) technologies is rapidly expanding the fields of applications of high-voltage direct current (HVDC) and FACTS in power systems. This chapter presents an overview of modelling of modular multilevel converter (MMC)-based HVDC transmission systems in electromagnetic transient (EMT)-type programs for off-line and real-time simulations. It introduces the MMC topology, and derives the four different MMC modelling approaches that are used in EMT-type programs. The chapter develops complete control system used for MMC-HVDC transmission. It presents the comparisons between different types of MMC models for deriving their advantages and limitations according to simulation needs. The chapter provides guidelines for the dynamic behaviour and computational performance for a practical MMC-based HVDC transmission system. It also presents the MMC model implementation using both CPU and field programmable gate arrays (FPGAs) technologies for real-time simulations.