Fuzzy Controller Based Seven Level Modified H-Bridge Inverter For Grid Connected PV System

摘要

This paper proposes a single-phase seven-level inverter for grid -connected photovoltaic systems, with a novel pulse width-modulated (PWM) control scheme. Three reference signals that are identical to each other with an offset value that is equivalent to the amplitude of the triangular carrier signal were used to generate the PWM signals. The inverter is capable of producing seven levels of output-voltage levels (V dc, 2Vdc/3, Vdc/3, 0 , .Vdc, . 2Vdc/3, .Vdc/3) from the dc supply voltage. And it recounts the development of a novel modified H-bridge single-phase multilevel inverter that has two diode embedded bidirectional switches and a novel pulse width modulated (PWM) technique. The top ology was applied to a grid-connected photovoltaic system with considerations for a maximum-po wer-point tracker (MPPT) and a current-control algorithm. Multilevel inverters offer improved output waveforms and lower THD. The circuit topology, modulation law, and operational principle of the proposed inverter were analyzed in detail. A FU ZZY control is implemented to optimize the performance of the inverter. MATLAB/SIMULINK results indicate that the THD of the Fuzzy Controller Circuit is much lesser. Furthermore, both the grid voltage and the grid current are in phase at near-unity power factor. By controlling the modulation index, the desired number of levels of the inverter's outp ut voltage can be achieved. The less THD in the seven-level inverter compared with that in the five- and three-level inverters is an attractive solution for grid-connected PV inverters