Shunt active power filter/STATCOM topology for medium/high power applications: Parallel inverters operating at different switching frequencies

This paper deals with a unique combination of two inverters those may work as an active power filter (APF) or a STATCOM. Two inverters are switched at different frequencies. The low frequency inverter takes care of the reactive power demand of the system and makes the source current in phase with the voltage, while, the high frequency inverter mostly compensates for the harmonics. In the limiting case, the low frequency inverter operates in square wave mode with minimum number of switching per cycle, thereby, also reducing the switching losses in the inverter. The high frequency inverter includes a L-C passive filter to mitigate the lower order harmonics and to bring down the operating voltage of the inverter to a very convenient level. It will be shown that the proposed combination has all the merits to work as a STATCOM or as an APF. Performance of the proposed topology is verified by MATLAB/SIMULINK and also confirmed by prototype experimentation.