unipolar pwm technique

.

Simulation of unipolar PWM technique

1) The devices in one leg are turned on or off based on the comparison of the modulation signal V with a high-frequency triangular wave. The devices in the other leg are turned on or off by the comparison of the modulation signal with the same high-frequency triangular wave.

2) In the Unipolar switching scheme the output voltage level changes between either 0 to -V or from 0 to +V. This scheme ‘effectively’ has the effect of doubling the switching frequency as far as the output harmonics are concerned, compared to the bipolar-switching scheme.

3) The pulse width modulation inverter is characterized by simple circuitry and control scheme that is SPWM technique to obtain controlled inverter output voltage and to reduce its harmonic content. Before analyzing the sine-modulated voltage waveform, it would be better to consider a pure dc signal as the modulating wave. The magnitude of the dc modulating signal is constrained to remain between the minimum and maximum magnitudes of the triangular carrier signal.