An improved Z-source multi-level inverter scheme for grid-connected photovoltaic systems

In recent decades, grid-connected photovoltaic (PV) systems have been increasingly utilized worldwide for their role in renewable energy generation and sustainability. Among power electronic configurations, the multi-level inverter (MLI) is famous for its efficiency in reducing total harmonic distortion (THD) and distributing power across several switches, enhancing power quality. However, using many switches increases energy losses and system complexity, making optimization crucial. Additionally, the power output from PV arrays is heavily dependent on environmental factors like temperature and solar irradiation, necessitating maximum powerpoint tracking (MPPT) techniques through advanced switching algorithms. These algorithms ensure that the system operates at its optimal point, extracting maximum energy from the PV array under varying conditions. Consequently, THD can be affected by these variations, complicating performance further. This paper proposes a Z-source-based MLI, providing additional benefits in power conversion efficiency and flexibility. This design employs a lower-frequency switching method for MPPT, executed in the Z-source part of the inverter during the shoot-through (ST) state, ensuring that THD remains unaffected by the MPPT process and improving system stability. This model is simulated in MATLAB to verify its performance under different conditions. Results illustrate an efficiency of over 96%, while maintaining a steady-state THD of 4.58%, confirming the effectiveness of the proposed approach.