Modeling, Control and Simulation of a Chain Link STATCOM in EMTP-RV

-This paper describes an alternative STATic synchronous COMpensator (STATCOM), by connecting a number of Gate Turn Off (GTO) thyristor converters in series on the ac side of the system. Each GTO converter forms one ‘link’ of a 1-phase, full-bridge Voltage-Source-Converter (VSC) and is referred to as a ‘Chain Link Converter’ (CLC). Each GTO of a CLS, is switched ‘ON/OFF’ only once per cycle of the fundamental frequency by using a Sinusoidal Pulse Width Modulation (SPWM) technique. Approximate models of a 3phase Chain Link STATCOM (CLS) using dq-transformation are used to design two controllers for controlling reactive current and ac voltage to stabilize the system voltage at the Point of Common Coupling (PCC). A novel technique, called the Rotated Gate Signal Pattern (RGSP), is used for balancing the voltages of the link dc capacitors. The performance investigation of the CLS system when used in a radial line is carried out under steadyand transient-state operating conditions by means of the simulation package; EMTP-RV and the results are presented.