PWM STATCOM Based Reactive Power Control by Using a Modular Multilevel Cascade Converter

The closed loop reactive power control by a Sinusoidal Pulse Width Modulation (SPWM) technique based static synchronous compensator (STATCOM) is used in modular multilevel cascade converter for reactive power control for welding machine. In these method five level cascade multilevel converters is used to implement the Hall Effect voltages on each H bridge side. And sense the voltage level of the each capacitor and controls the amplitude of the carrier signal and also balance the capacitor voltages the digital signal processor is used. As a result the STATCOM output voltage can be controlled by the modulating index. It improves the harmonics of the resultant STATCOM output voltage only appear as sidebands centered around the frequency of 2Nfs. Its multiples provided that the voltage across the dc capacitor of each inverter is the same. Here N is the number of H-bridge inverters and fs is the frequency of triangle carrier signals.