PROJECT TITLE :

Impact of Switching Harmonics on Capacitor CellsBalancing in Phase-Shifted PWM Based CascadedH-Bridge STATCOM - 2016

ABSTRACT:

The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power distribution in the cells of a cascaded H-bridge-primarily based STATCOM when using section-shifted pulse width modulation. The case of high- and low-switching frequency for the converter cells is investigated and therefore the interaction between voltage and current harmonics is analyzed. It is shown that in each cases, this interaction results in an uneven power distribution among the cells in the same section leg, resulting in drifting of the dc-capacitor voltages and thereby the need for correct stabilization management loops. It is additionally shown that the selected frequency modulation ratio affects the active power distribution among the cells. In particular, the choice of a noninteger frequency modulation ratio helps in providing a additional uniform power distribution among cells of the same section leg, thus contributing to the capacitors balancing. A methodology for optimal selection of the frequency modulation ratio is given. Theoretical conclusions are validated through simulation and experimental results.