Harmonics and DC offset elimination scheme for buck-boost converter fed single phase inverter

The DC source provided by most of the renewable energy sources are need to be interfaced to the grid with the aid of at least one inverter. Normally the renewable energy sources provide low voltage. So a buck boost converter is provided at the source side to buck/boost the voltage to the required level. Commonly inverters with a variation of Sinusoidal Pulse Width Modulation are used. Also the inverter requires a passive filter to reduce the harmonic content and achieve the permissible level of Total Harmonic Distortion. Two disadvantages of this this method are, the system becomes bulky and costly due to the use of filter also there will be losses of switching action of the semi conducting switches of both the converter (one) and inverter (four). To overcome the consequence, the harmonic content at the output of inverter is continuously monitored and handled by harmonic cancellation scheme. THD at the output is to be achieved below the acceptable level by controlling the Boost converter by improved Sinusoidal Pulse Width Modulation (SPWM) technique. Improved SPWM consists of combination of two controlling schemes, DC elimination scheme and harmonics elimination scheme.