In this paper multistage grid connected inverter for solar PV based system and the types of multilevel inverter are discussed. The conventional line commutated inverters have square shaped waveform of line current which generates high harmonics and also produces excessive heat which causes damage to the winding of transformer. Alternatively, multilevel inverter reduces harmonics and gives output current waveform which is almost sinusoidal in nature. Basically, multilevel converter technology is based on the synthesis of the ac voltage from several different voltage levels on the dc side. i.e. by increasing of DC voltages, the levels of the output increases, which produce a staircase wave which approaches the sinusoidal wave with lower harmonic distortion. In the present work, a multilevel line commutated inverter topology has been proposed and analysed which improves the wave shape and hence reduces the total harmonic distortion (THD) of the line current in a grid connected line commutated inverter. Moreover, the performance of the proposed topology is far better than the conventional line-commutated inverter. The simulation is carried out in MATLAB/SIMULINK environment.
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