Dynamic averaged models of VSC-based HDVC systems for electromagnetic transient programs

High Voltage Direct Current (HVDC) systems based on Voltage-sourced Converter (VSC) technologies present a bright opportunity in a variety of fields within the power system industry due to their recognized advantages in comparison to conventional line-commutated converter (LCC) based HVDC systems. VSC-HVDC technology combines power converters, based on IGBTs (Insulated Gate Bipolar Transistors), with dc links to transmit power in the order of thousands of megawatts. In addition to controlling power flow between two ac networks, VSC-HVDC systems can supply weak and even passive networks. VSC-HVDC systems present a faster dynamic response thanks to its Pulse-width Modulation (PWM) control in comparison with the fundamental switching frequency operation of traditional HVDC systems.;Detailed representation of VSC-HVDC systems in Electro Magnetic Transient (EMT) programs includes the modeling of IGBT valves and must normally use small integration timesteps to accurately represent fast switching events. Computational burden introduced by such a detailed models complicates the study of steady-state and transient events highlighting the need to develop more efficient models that provide similar behavior and dynamic response.;The objective of this thesis is to develop, test and validate averaged models to accurately replicate the steady-state, dynamic and transient behavior of VSC-based HVDC systems in EMT-type programs. These simplified models represent the average response of switching devices and converters by using averaging techniques involving controlled sources and switching functions. The work also contributes to the development of detailed VSC models used to validate the proposed average models. The detailed models developed include two- and three-level converter topologies and the most recent Modular Multilevel Converter (MMC) topology. Comparison of different converter topologies suitable to VSC-HVDC transmission, including their advantages and limitations, are also discussed.;A control system is implemented based on vector control which permits independent control both active and reactive power (and/or voltage) at each VSC terminal. Available modulation techniques are presented and compared in terms of performance and power quality. The modeling approach and models accuracy are validated, and their computing performance compared, for four test cases including an actual point-to-point VSC-HVDC interconnection between France and Spain and a multi-terminal VSC-based (MTDC) system used to integrate large amounts of offshore wind generation.