Grid Connected Multi Level Inverter with Power Converters for Renewable Energy System

A single-phase nine-level inverter for gridconnected photovoltaic systems, with pulse width-modulated (PWM) control scheme is proposed. Three reference signals that are identical to each other with an offset that is equivalent to the amplitude of the triangular carrier signal were used to generate the PWM signals. The inverter is capable of producing nine levels of output-voltage levels from the dc supply voltage. Multilevel inverters offer improved output waveforms and lower THD. A PWM switching scheme for the multilevel inverter is generally preferred. By controlling the modulation index, the desired number of levels of the inverter's output voltage can be achieved. The DC-DC converters based topology applied for high-voltage and high-power applications were introduced. The converter is configured such that the boost-half-bridge (BHB) cells and voltage doublers are connected in parallel and in series to increase the output voltage and the output power. In addition to reduced device voltage and current ratings by the connection, the converter has the advantages of high-step-up voltage gain with significantly reduced transformer turn ratio, low input current ripple due to interleaving effect, zerovoltage switching turn-ON of switches and zero-current switching turn-OFF of diodes. The converter has reduced volume of input and output filters resulting from the interleaved switching. Another advantage provided by the multiphase converter is output ripple cancellation, which results in increasing the effective output frequency.