Modified sinusoidal PWM

[sam781]

Hi goldsmith,

I don't see any problem right now. Just thinking about the timing to make a 50Hz PWM signal using Microcontroller. I think, timing is very important to reduce higher order harmonics.

Again thank you a lot for your suggestion/advice/clarification of each issue throughout the thread.

 

[sam781]

I want to observe the harmonics contents of PWM, SPWM and Modified SPWM wave to verify our learning. :smile:
How it can be done?

 

[FvM]

For simple "modified" sine waveform, the harmonic content can be easily derived mathematically, e.g. referring to fourier series. For more complex waveforms and PWM with arbitrary PWM frequencies, it can be best determined by numerical methods, e.g. using SPICE, Matlab or MS Excel.

A simple way to generate low harmonic distortion is a sine PWM with sufficient high pwm frequency. The only disadvantage compared to other methods are higher switching losses.

 

[sam781]

I can generate PWM in matlab. Could you please let me know how to determine harmonics contents? This is just for learning

 

[FvM]

Magnitude of fourier transform.