The present global pursuit of power grid decarbonization is heavily relying on increased exploitation of renewable generations such as solar and wind, and voltage source converter based HVDC transmission systems to evacuate the generated renewable power to the consumption centers. It causes the industry to experience exponential rise in demand for electrical engineers with knowledge of both power electronics and power systems. In this line, this tutorial aims to bridge that knowledge gap by introducing the target audience to various types of voltage source converter HVDC transmission systems, which cover device and system aspects, for examples, voltage source converter topologies (two-level converter, three-level neutral-point clamped converter, and modular and hybrid multilevel converters) and their operating principles, modulation techniques, control principles and strategies, and system behaviour under normal and abnormal conditions, including merits and limitations. In addition to explanations of the fundamental theoretical concepts and relevant equations that governed the operation of VSCs, prerequisites for VSC controlled operation; manipulation of phase and magnitude of modulating signals to control active and reactive power and to extend converter ac voltage control range; manipulation of positive and negative phase sequence to achieve tangible control objectives at system level, converter P-Q and Q-V capability curves and limiting factors, etc., will be covered and supported by simulations. Also, ac and dc fault ride-through (low-voltage and high-voltage) and their impact on converter design and control considerations and practical countermeasures will be discussed. Small part of the tutorial will be dedicated to discussion of the drivers for grid forming converters, key fundamental differences between grid forming and grid following controls , and potential implications of grid forming control on design considerations of VSCs and behaviors at system level. To support research students and simulation engineers, various modelling methods of the voltage source converters will be discussed and supported by simulations and their merits and demerits; for examples, EMT (detailed switched, Thevenin and Norton equivalent based on Dommel implicit integration with two-state switched resistors, switching function, averaged) and RMS.
