SERIES CONNECTED VOLTAGE-SOURCE CONVERTER MODULES FOR FORCE-COMMUTATED SVC AND DC-TRANSMISSION

In force-commutated SVC and DC Transmission stations, series-connected , multi-converter modules are necessary to build up the dc link voltag e rating. Based on digital simulations of 8 modules, it is shown that the Total Harmonic Distortion (THD) of 5% can be achieved from harmoni c cancellations by using phase shifting of the triangular carriers in the Sinusoidal Pulse Width Modulation technique. The requirement of th e dc link capacitor size to ensure ripple-free dc voltage is studied. The 8-module case-study points to the ability to achieve 1% THD for hi gher voltage rating by increasing the number of modules connected in s eries.