This thesis focus on high voltage direct current (HVdc) energy transmission using modular multilevel converter (MMC) based terminals. It provides a brief comparison between different HVdc technologies, focusing on voltage source converters (HVdc-VSC) with the MMC-based terminal emerging as the topology of choice for ratings less than 1 GW. The controllers for a two-terminal HVdc-link are analyzed and Matlab/Simulink(TM) simulation models are presented. The simplified models and full Matlab/Simulink(TM) based model are used to select the gains for the MMC controllers. Simulation results carried out on the full model validated the proposed methodologies. A new control technique that eliminates the voltage sensors on the grid side normally used to synchronize the MMC-based terminal with the grid is proposed. The performance of proposed technique was evaluated through Matlab/Simulink(TM) simulations by considering inverter operation. The sensorless technique is able to synchronize a MMC-based inverter terminal to a grid under non-ideal conditions as well to accurately detect changes in the grid voltages. Finally, an analysis of the impact that a 15-kV SiC IGBT would have on HVdc MMC-based terminals is presented. The analysis evaluates parasitic inductances within the sub-module (SM) of an MMC, changes on the required SM capacitance, and impact on the voltage waveform THD. The evaluations showed that the 15-kV SiC IGBT would be only suitable if the module is rated 400 A or greater.This thesis focus on high voltage direct current (HVdc) energy transmission using modular multilevel converter (MMC) based terminals.
|Title||:||High Voltage Direct Current Energy Transmission Using Modular Multilevel Converters|
|Author||:||David Alejandro Guzman|