The multi-level H-bridge DC-AC inverter has been widely used in the AC power grid-connected photovoltaic power system. Because, its output waveform is high quality and low electromagnetic interference. Hence, it is widely used in many large-scale photo voltaic (PV) systems. The most common application of many H-type bridges square wave inverter cascaded series to approximate the stairs-sine waveform. Multi-level H-bridge inverter can output different pulse width modulation (PWM) waveforms, then cascades them to change harmonic properties and affecting the inveter output waveform quality. The main issue of this thesis is to research how to improve the operational characteristics of the multi-level inverter, and the relevance inverter cascading series and power quality.