Dynamically change the dead time in 6PWM mode

[SnifMyBack]

Hi!

I'm currently working on a "custom" V/Hz controller with an ESP32 in 6PWM mode. I'm facing a problem where I need to be able to change the deadtime value even after the driver has been initialized. It is critical because I will be driving different IGBT module where the timming is not always the same.

I though of deleting the instance of the driver and starting again but it doesn't seems to possible (with the little knowledge in programming that I have at least).

Is there an alternative or do I need to wait for a possible update that will implement this kind of feature?

Thanks!

[runger1101001]

Hey, you're the first person to ask for this, I think. I agree, we should make both frequency and dead-time dynamically settable. At the moment it is not possible using SimpleFOC functions.

But, I think you can use the following code to set the dead time directly, bypassing the library (in this snippet dead_zone is the desired dead-time in terms of the total duty cycle, so dead_zone = 0.02 means 2% dead-time):

HardwareTimer *HT = ((STM32DriverParams*)driver.params)->timers[0];
  uint32_t dead_time_ns = (float)(1e9f/PWM_freq)*dead_zone;
  uint32_t dead_time = __LL_TIM_CALC_DEADTIME(SystemCoreClock, LL_TIM_GetClockDivision(HT->getHandle()->Instance), dead_time_ns);
  if (dead_time>255) dead_time = 255;
  if (dead_time==0 && dead_zone>0) {
    dead_time = 255; // LL_TIM_CALC_DEADTIME returns 0 if dead_time_ns is too large
    SIMPLEFOC_DEBUG("STM32-DRV: WARN: dead time too large, setting to max");
  }
  LL_TIM_OC_SetDeadTime(HT->getHandle()->Instance, dead_time); // deadtime is non linear!

[runger1101001]

Another assumption made here is that you are using all PWMs from the same timer. If you're using more than one timer, then you need to set the dead-time for each timer in this way.

[SnifMyBack]

Thanks for the really fast answer! I'm not in front of my computer at the moment but I will try to implement the said patch for the ESP32 platform. As for the timer selection, I use the default behavior of the library as I didn't specify any.

Another feature that would be awesome is the ability to change dynamically the active on low or high.

I can look to implement this myself but I'm not an expert in programming. What I can do, though, is sharing the code behind the V/Hz controller I'm developing. It's not pretty but it works as tested today on a big 3 phases motor!

Thanks again!