Performance assessment of five-level inverters for PV systems with capacitor voltage balancing and PD-PWMOA

To solve the limitations of traditional two-level inverters to medium-to-highpower photovoltaic(PV)systems,such as increased switching stress,electromagnetic interference,and total harmonic distortion(THD)as well as high cost and complicated structure,multilevel inverters are suggested to be more viable.In this paper,two typical five-level inverters potential to be used with PV cells,including a flying capacitor-based inverter and an active neutral point clamped(ANPC)inverter,are analyzed and compared.The control technique based on phase disposition modulation and redundant state selection is adopted,ensuring that the capacitor voltages in the active converter are balanced and controlled correctly.By simulating the system with MATLAB,the results show that both inverters are capable of reducing the THD to extremely low levels,contributing to output waves with improved waveform characteristics before and after filtering.Moreover,the waveform quality of the ANPC inverter is better with lower THD even without a filter applied to the output.This successfully demonstrates the feasibility of the implemented control strategy.