Design and analysis of a grid-tied single phase nine level asymmetrical inverter

The supply voltage levels of the multilevel inverters (mlis) that are widely used nowadays are the significant limiting parameters. the major drawbacks of conventional two-level inverters used in the high power systems are the insufficient switch power against the power range, non-sinusoidal output waveforms, and increasing line transformer requirements. furthermore, the higher switching frequency requirement to reduce the total harmonic distortion (thd) increases the switching losses. this study presents the design and analysis of a controller that is performed by using matlab/simulink environment. the asymmetrical mli topology is constituted in trinary dc supply structure, and the switching frequencies are generated in sinusoidal pulse width modulation (spwm) scheme. the grid connection of the inverter is controlled by the implemented proportional-integral (pi) controller and phase locked loop (pll) control algorithm. the proposed control method is compared to conventional controllers in terms of thd rates and observer structure. it is observed that the designed pi controller decreases the thd ratio, with higher dynamic response. the improved control mechanism is tested under open-loop, pi controlled, and pi-pll controlled structures to determine the thd ratios where the proposed single phase grid-tied control method is verified. the performed analysis results have shown that the pi and pi-pll controllers provide almost same result, but the pi-pll controller draws faster dynamic response comparing to pi control algorithm. besides, the proposed pll controller ensures the grid connection of inverter without complex control methods or complex algorithm requirement.