Multilevel Converter With Nearest Level Control for Integrating Solar Photovoltaic System

This article presents a new Scott-ternary solar multilevel converter (ST-MLC)-based solar photovoltaic (PV) system for medium voltage applications. This system employs a single solar PV array as an input source and two voltage source converters (VSCs) to feed a three-phase grid. Solar power is fed from a two-phase to a three-phase medium voltage grid with balanced grid currents. The legs of VSCs are cascaded to form a two-phase system. The multiwinding transformers are connected in a Scott manner to develop a nine-level three-phase power conditioning system. The turn ratios of the transformers have ternary progression for the generation of higher levels. The modeling of the system is presented, and a closed-loop nearest level control strategy is incorporated to have minimum losses. Simulation results show the performance of the solar PV system under steady-state and dynamic irradiance. Varying solar profile is considered on basis of the daily average global solar irradiance from the geographical information system for New Delhi, India. The harmonic performance is analyzed for the converter voltage and grid current. Moreover, a detailed comparative analysis is covered for the ST-MLC to evaluate its superiority over its existing counterparts. Performance validation is done in a real-time test bench to validate the control and operation of the large-scale solar PV system.