Multi-Objective Cascaded Control Strategy for Grid-Connected Photovoltaic Energy Conversion System Using a Five-Level ANPC Inverter

This paper proposes a nonlinear cascaded control strategy for a grid-connected Photovoltaic Energy Conversion System (PVECS) based on a triphase five-level Active Neutral Point Inverter (ANPC). The control structure encompasses multiple control objectives to fulfill the demands and requirements of the PVECS, including Maximum Power Point Tracking (MPPT), Power Factor Correction (PFC), and balancing the flying and DC-link capacitor voltages. To decrease the computational complexity of the modulation algorithm, a zero Common Mode Voltage (CMV) technique is utilized, limiting the number of voltage vectors from 125 to only 19. Additionally, a priority algorithm is introduced, allowing for the decoupling of control between the flying voltages and the neutral point potential. The effectiveness of the proposed controller is validated through simulation results in the MATLAB/Simulink environment. These results demonstrate that the proposed controller can achieve satisfactory performance under parameter variation and variable weather conditions.