STATCOM DC bus voltage control and switching strategy analysis

Static Synchronous Compensators (STATCOMs) are employed within electrical networks to dynamically provide Reactive Power support to the when necessary. In 2012, Ergon Energy (the regional electricity supply utility in Queensland, Australia) commissioned its first STATCOM into the sub-transmission, at St. George Substation, and within its first year of operation experienced a number of trip operations on this device. Due to the limited knowledge of the operational characteristics of this device Ergon Energy’s Engineering team decided to investigate further and attempt to model the D-VAR® STATCOM. This dissertation is the result of this work. While the initial intent was to fully develop a three phase model of the STATCOM, time and complexity constraints limited the outcome of the initial aim, but the following text presents a comprehensive depiction of the findings of the simulation results and establishes a solid base to any further work towards this initial aim. By deriving a number of equations from first principles and applying these to develop a mathematical model which was implemented in MATLAB®, this project uncovers a number of interesting arguments which explain some of the operational characteristics of the D-VAR® STATCOM. Considering the limitation of information from the manufacturer, this project deals with an open-loop controlled STATCOM in an attempt to investigate the DC bus levels of the STATCOM. A number of analysis was carried out, including: - The Pulse Width Modulation (PWM) switching strategy to verify and explain its role in the DC bus operation, - The effects of changes in th