Abstract: Energy demand is increasing day by day. In order to meet this energy demand renewable energy sources have to be incorporated. Renewable energy sources like fuel cells, pv cells etc. produces DC voltage. But most of the house hold and industrial purpose require AC voltage. So this DC (direct current) voltage has to be converted into AC (alternating current) voltage. For this power electronic inverters can be used. Multilevel inverters has got wide spread acceptance as it can synthesis almost sinusoidal wave form. This paper presents an inverter which can give a seven level AC output without variation in its voltage amplitude, from a variable DC source. Here a boost converter is introduced as a front-end stage. This DC-DC conversion helps to stabilize the output voltage. A new class of multilevel inverter with coupled inductor was introduced in the second stage to get a seven level AC as output. The working principle of DC-DC converter and the inverter are explained. The circuit is tested with different DC voltage and found to give the same output voltage waveform. The circuit has been simulated using MATLAB/Simulink tool and a prototype is made to verify the validity and performance of the circuit.
Keywords: Multilevel inverters (MLI), Total harmonic distortion (THD), neutral point clamped (NPC) inverters.