Single Phase Seven Level Inverter

The given paper presents a review about the hardware design and implementation of single phase seven level inverter with Pulse Width Modulated (PWM) control scheme. The input to the given inverter is a DC source (Vdc) and it is capable of producing output of seven level (Vdc, 2Vdc/3, Vdc/3, 0, -Vdc, -Vdc/3, -Vdc/3). As more steps are added to waveform, the harmonic distortion of the output waveform decreases. The switching devices used are 25N120 IGBT and diodes. Control circuit for implementing the H-bridge inverter is done by using the micro-controller. The system proposed in given paper is having lesser number of switching devices which reduces the complexity of the circuit and a simple control circuit is employed using the micro-controller. The multi level inverters provides nearly sinusoidal output waveform, output current with refined harmonic profile and switching losses that are less than the conventional two level inverter and hence smaller filter size is required. The main application of this system is directly delivering the Photovoltaic generated energy to the power system networks by using this seven level inverter (SLI) as grid connected inverters.