A Modified Lyapunov Function Based Control Strategy for Single Phase Cascaded H-bridge Multilevel Inverter with Nonlinear Loads

In this paper, a modified Lyapunov function based control strategy that assures global stability is proposed for single phase cascaded H bridge multilevel converter feeding nonlinear loads. The Lyapunov function is formed from the energy stored in the inductor and capacitor. The Lyapunov function based control strategy proposed in the literature for the single phase converter assures global stability with only output voltage and current control. But the DC link voltages of the multilevel inverter fluctuate due to the disturbances in the input and output side. Hence the Lyapunov function based control strategy is modified by including a DC link voltage control is proposed for the multilevel inverter. Detailed analysis has been conducted to verify the effectiveness of the proposed system and is compared with the conventional control strategies. A fast dynamic response and lower distortion in output voltage is obtained with the proposed strategy compared to the conventional control strategies. Simulation and experimental results from a laboratory scale prototype is demonstrated to assess the performance of the suggested control scheme.