SELECTIVE HARMONIC ELIMINATION-PULSE-AMPLITUDE MODULATION FOR CASCADED MULTILEVEL INVERTER-BASED STATCOM

Static synchronous compensator (STATCOM) has played a key role in the improvement of power handling capability of the transmission line and alleviated power quality problems. High-quality output voltage with low-switching frequency is of prime interest in the multilevel inverter (MLI) employed in static synchronous compensator (STATCOM), which can be achieved by selective harmonic elimination (SHE) methods. In this paper, the equal-area criteria-based SHE-pulse amplitude modulation (SHE-PAM) method is presented, which works for a cascaded H-bridge (CHB) MLI having a higher number of levels where the conventional SHE methods fail. The SHE-PAM is implemented by employing buck converters to adjust the dc-link voltage at the input of CHB with constant switching angles. Instead of traditional non-linear transcendental SHE equations, this method works with linear equations. Due to drastically reduced computational burden, SHE-PAM is implemented online for STATCOM with great ease. Reactive power demand is achieved using closed-loop current and voltage controllers for both STATCOM and buck converters. A simulation study is carried out to validate the performance of the SHE-PAM method employed for nine-level CHB MLI-based STATCOM.