Flying capacitor voltage balance and neutral point voltage regulation of PV array fed active neutral point clamped converter in real-time HIL

This study deals with a new control strategy for flying capacitor (FC) based multilevel converter, in order to attain the desired reference value for five-level output voltage in active neutral point clamped (ANPC) converter. The balancing of capacitor voltages is one of the crucial aspects of grid-tied photovoltaic (PV) fed ANPC converter. The accurate reference voltage for FC is required to experience minimum power pulsation and capacitor voltage imbalance. An offset injection-based FC voltage regulator is implemented to track the desired voltage reference for FC. A simple proportional–integral controller generates the offset signal, which is added to the sinusoidal modulating wave to eliminate the FC imbalance. Moreover, neutral point voltage (NPV) balancing is achieved with the help of DC component injection control. The DC–AC power transfer, FC balance, NPV balance and unity power factor operation are achieved simultaneously. The performance of the closed-loop controller for grid-tied PV-fed ANPC converter is analysed at constant and variable irradiances. The system is modelled in MATLAB/Simulink for offline simulation. Furthermore, offline simulation results are validated using real-time controller hardware in loop (HIL) test bench. Moreover, active power is injected into the AC grid seamlessly and results are found compliant with the IEEE 519 standard.