Optimal Synthesis of Output Voltage Waveforms for Multilevel Cascaded Single Phase DC-AC Converters

Multilevel inverters are very interesting alternative for medium and high power applications. One of the most flexible configurations of this type is the cascaded H-bridge multi-cell Multi-level inverter. Multi-level cascaded H-bridge single-phase DC-AC inverter, when appropriately controlled by unipolar PWM scheme provides very good output voltage waveforms. This paper presents the double Fourier series approximation of the converter switching function which provides the condition for maximum DC input voltage utilization and the elimination of the first harmonic component of the output voltage waveforms. Experimental results validate the proposed method for determining the modulation signals required to generate a reference output voltage.