1. Need to design solar inverter dc to ac using pure sine wave PWM. I am reading a bit and this is what understand. I am using MCU with FPU enabled.
2. Have to change output freq from 1-400Hz(depending on user input) & output ac voltage from 110Vac-300Vac(depending on user input)
3. Currently i am understanding how to change freq:
a) Whatever I have read on internet is using swtiching freq 20Khz or higher for pure sine wave since its outside audible range. So i am using 20Khz here. I dont know if its ok or higher need to be selected, what is criteria for it?
Since I am using IGBT of 10Amps for application, so cannot go above 20Khz, as they have limitation of their own.
With 20Khz , PWM time period = 1/20Khz = 50us.
b) Then I read to divide sine wave into equal parts some on intenet used 100, some 200 some 10. What is criteria for it?
I am chosen 100 parts since it will divide 360 degree into 3.6 degree each.So an array of 100 values is made
arr[n] = Sin(n*Pi/180) where n varies from 0 to 99
Is it ok?
Then PWM will start with width variation and after every degree time period, corresponding PWM On time be selected, whereas PWM timer period is fixed at 50Hz so that switching freq is 20Khz always.