A positive reference PWM strategy based on multi-switching DC voltage sources converter for insulation testing

This paper presents a positive reference pulse width modulation (PWM) technique based on multi-switching dc voltage source converter. This technique aims to reduce the switching losses and the number of devices. Five modules of dc voltage source are used to generate 11 levels of dc multi-step signals, and a single H-bridge is used to generate a new unipolar PWM technique. The modulation unit consists of a triangular carrier signal at 10 Hz and a positive reference signal at 0.1 Hz. The generated high voltage very low frequency (VLF) waveforms with frequency of 0.1 Hz, can be used in the insulation testing. Due to the very low frequency of the signal, the total harmonic distortion (THD) value of the created hardware prototype using the proposed technique is evaluated through computer simulation and compared with the cascaded H-bridge (CHB) converter. The experimental results have shown that the created waveform is complied with the IEEE 400.2 standard.