Design and Simulation of Cascaded H- Bridge Quasi Z-source Multilevel Inverter for Photovoltaic Applications

Abstract: In this paper, a cascaded five level Quasi Z-Source inverter is proposed for photovoltaic applications. The proposed topology employs an LC network between the DC source and inverter circuitry to achieve boost as well as inversion operation. The output voltage of the proposed inverter is controlled by using modulation index and shoot through state. Various modulation strategies have been reported in the literature for the proposed topology. But this paper focuses on the implementation of simple boost, maximum boost and constant boost control strategies with third harmonic injected phase shift PWM. The performance parameters of the proposed topology are computed and comparison is provided for all the three control strategies. Simulations of the circuit configuration for the above mentioned control methods have been performed in MATLAB/Simulink and the results are verified.

Keywords: Quasi Z-Source inverter, Simple Boost, Maximum Boost, Constant Boost control, Pulse Width Modulation (PWM), Phase shifted pulse width modulation (PSPWM)