A Flyback Converter Based Asymmetrical Cascaded H-Bridge 27 Level Grid Connected Inverter From A Single Source Using FPGA

Multilevel inverters(MLI) has many remarkable features when compared to the traditional two level inverters such as high dc link voltages, reduced harmonic distortion, less voltage stress and low electromagnetic interference. In spite of these advantages it have some major disadvantages when used for high level applications such as higher number of power switches, voltage balancing issues in H-bridge cells, higher number of dc sources and complex pulse width modulation (PWM) techniques. In order to eliminate these issues a number of MLI topologies have been proposed in recent papers. The project deals with a 27 level multilevel inverter utilizing reduced switches and a single source which is connected to the grid. A multi winding flyback transformer is used to provide power to the individual H-bridge cells. PODSPWM technique was employed to provide switching pulses. This solution reduces the cost, size, switch count and improve the efficiency. The simulation of the proposed MLI was carried out and satisfactory results were obtained. A FPGA controller wass used to achieve MPPT, inverter control as well as islanding detection. The simulation and prototype implementation for an input of 20V dc and 220V_rms output was carried out and satisfactory results were obtained.