A static synchronous compensator (STATCOM) using parallel inverters operating at different switching frequencies

Performance of a static synchronous compensator (STATCOM) is presented in this paper. A low frequency and a high frequency inverter are used for this purpose. The low frequency inverter operates in square wave mode in the limiting case, when the STATCOM operates like a static VAR compensator (SVC). Minimum numbers of switchings per cycle in the square wave inverter (SWI) make the switching losses low. However, it will inject huge amount of harmonics to the point of common coupling (PCC). The 2^nd inverter that operates at a higher frequency is used to compensate for the harmonics. Therefore, the combination of the SWI and the high frequency inverter (HFI) is proposed in this paper for VAR compensation. The HFI is connected through a passive L-C filter. Such hybrid configuration has the advantage of operating the HFI at a lower voltage level. As the HFI is only compensating the harmonics generated by the SWI, the power rating of the inverter is less. Performance of the proposed topology is verified by MATLAB/SIMULINK and also confirmed by prototype experimentation.