Experimental and Simulation Study of Harmonics in Asymmetric Multilevel Inverter Fabricated Using Four Units

This research document presents experimental and simulation studies on THD ( total harmonics distortion ) in the output voltage of a single-phase multi-level inverter built with four full-wave bridge inverters connected in cascade. Four MOSFET devices were used for each Hbridge unit. Four independent DC power supplies of different values were connected to the four Hbridge units. Proper gate drive pulses for the 16 MOSFETs of the four Hbridge units to change the switching states were generated on a microcontroller-based Arduino board. Simple microcontroller programming codes was generated to simplify the complex gate control pulses of MOSFETs. It is observed that small number of power switching devices are used to obtain different levels of output voltage. The proposed system was experimentally tested in the laboratory to estimate total harmonic distortion. This experimental study also shows that the THD of the proposed inverter output voltage is decreased when voltage steps at the of the output voltages is increased. The proper switching angles in equal steps has been maintained by using proper drive pulses for power devices to reduce harmonic distortion.