Development of multi-level inverter for power quality enhancement

The objective of this thesis is to develop and improve the performance of the multi-level inverter. Two paths have been followed in the development and improvement works. The first one represents the off grid connected multi-level inverter. The trend is focused to increase the number of the level at the output of the inverter while the inverter represents the main energy source. In the second path followed in the studies, the grid-connected multi-level inverter has been considered. Power quality enhancement has been done by developing the control unit of grid connected multi-level inverter in such a way to ensure the stability of the system against the system voltage sag. The multilevel inverters designed in the thesis are both simulated using a computer software program and implemented in hardware. The developed inverters are multilevel and hybrid inverters. Conventional inverters give five levels in the output waveform. These inverters contain two H-bridge circuits to generate different levels at the output while the hybrid inverter developed in the thesis includes three H-bridge circuits to form different levels at the output. Moreover, developed hybrid inverter can also operate in conventional mode when it is supplied with equal sources. The output of each H-bridge has been connected in a cascaded form. The sum of the individual H bridges voltages represents the final inverter voltage. Experimental results on the developed circuits gave satisfactory results and confirmed the accuracy of the design. Key Words: Low Voltage Ride Through (LVRT), Photovoltaic Panel (PV),Multi Level Inverter, Maximum Power Point Tracking (MPPT), Active And Reactive Power Control