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 chain link STATCOM (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 3-phase CLS using dq-transformation are derived 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 steady- and transient-state operating conditions by means of the simulation package; EMTP-RV and the results are presented.