On the Effect of Inherent Time Delay in Stability Analysis of a Single Phase H-Bridge Inverter

Detailed fourth order parasitic model of a dc-ac H-bridge inverter has been constructed, where instead of the common assumption of zero delay in control circuit, inherent time delay has been accounted for in analytical model by first order Padé approximation. The objective of this paper is to investigate the effects of inherent time delay on stability analysis by a combination of Filippov method and Floquet theory, wherein stability boundaries in control and power circuit parameter spaces have been plotted for ideal condition without and realistic condition with time delay. Results have revealed that time delay drastically aggravates onset of Hopf bifurcation in parameter spaces. However, increasing time delay causes earlier onset of period-doubling bifurcation only by a meagre amount. Critical delay threshold has also been determined analytically. While qualitative verification of analytical results has been demonstrated by plotting waveforms obtained by numerical simulations; both qualitative and quantitative verification have been achieved by plotting bifurcation diagrams.