Hi,
I am trying to achieve Sine PWM in a 3-phase inverter (actually 2 phases and a neutral). I have looked around on this forum and various TI resources and have gathered bits and pieces about the various details involved in implementing this. I need some help putting it together. Also, I'm trying to achieve open-loop control now and will move to closed loop control soon. I am trying to implement open-loop in a way that will make transition to closed-loop easier for me.
I'll be using 3 ePWM modules. PWM is brought about comparing the value of CMPA/CMPB to the TBCTR. The value of CMPA is modulated according to a sine wave of desired frequency, while the triangular wave is the TBCTR counting up to TBPRD and down again (using Up-Down counter). Now, some of the code snippets I've seen around here use a 512 point look-up table which gives a 915 Hz sine signal, but I'm aiming for a 50-60 Hz signal. My switching frequency/PWM frequency is 10kHz. Assuming 60 Hz signal and 10 kHZ PWM frequency, I'll need 167 data points, which I'm not sure how to get.
My other line of thought was to generate a sine-wave using the SGEN module specifically the SGENT_1 or SGENT_2. However, their outputs vary between (hex) -7FFF to 8000. How do I modulate my CMPA value according to these outputs?
Also, am I making a mistake anywhere here?
Thanks,
Sandesh
