Multilevel power converter with variable frequency and low constant total harmonic distortion

This paper describes the design and implementation of an H bridge multilevel converter with independent sources and five levels in the output voltage waveform, operating at variable frequency and a low constant harmonic distortion (THD) independent of frequency. With the use of dsPIC technology the power inverter replicates a calculated modulation, with firing angle necessary to emulate the 360° of the sine wave signal through a five-step levels and without low-order harmonic content (h <= 20). The converter changes the frequency of the modulation from 2.7 to 120 Hz in steps of 0.1 Hz, while maintaining constant wave form and thus the time invariant THD. This aims to provide a system capable of varying the frequency of the voltage and maintain a good power quality so that it can be applied and implemented in the speed control of AC motors.