An Effective Double Frequency Ripple Suppression Based on Sliding-Mode Control for Cascaded Multilevel Quasi-Z-Source Inverters

In this paper, a robust and efficient sliding mode control is proposed for a seven-level quasi-Z-source inverter. The proposed method simplifies the control of the entire system while suppressing the double frequency ripple (DFR) in inductor current and offering excellent features of the sliding mode control such as fast response and robustness. In this method, the values of modulation index and shoot through duty cycle are generated by the sliding surface functions. These functions are passed through separate boundary layers so that they become appropriate signals to be employed in the SPWM process. Simulation results confirm that the proposed method not only possesses robustness, fast response and easy implementation, but also reduces the DFR in inductor current. Simultaneous use of sliding mode control and multilevel qZSI has also enhanced the quality of the output voltage under linear and nonlinear loads.