Cascaded H-Bridge Five-Level Inverter for Grid-Connected Photovoltaic System Using Proportional-Integral Controller

Photovoltaic power generation is a promising alternative source of energy and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal, and so on. In photovoltaic power generation, multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter, and cascaded H-bridge multilevel inverter, are widely used in these multilevel inverters. Among the three topologies, cascaded H-bridge multilevel inverter is more suitable for photovoltaic applications since each photovoltaic array can act as a separate direct current source for each H-bridge module. In this paper, a single-phase cascaded H-bridge five-level inverter for grid-connected photovoltaic system using proportional-integral controller is presented. Sinusoidal pulse width modulation technique was used for eliminating the harmonic distortion. The cascaded control strategy enables tracking of the maximum power point of distinct photovoltaic strings and allows independent control of the direct current-link voltages. The performance of single-phase cascaded H-bridge five-level inverter with respect to harmonic content and number of switches is simulated using MATLAB/Simulink. A hardware prototype is developed to verify the performance of the developed system. The results of hardware are compared with the simulation results. The proposed system offers improved performance over conventional two-level inverters.