DSC for FOC of three phase induction motor

[stepan_podhorsk]

Hello,

I am going to implement the field oriented control of three phase induction motor. I need below given operating modes of the ADC and PWM:

1) Time base of the PWM operates asynchronously of the AD conversion i.e. AD conversion is started arbitrarily in respect to the PWM period. In this mode the PWM carrier frequency is variable.

2) Time base of the PWM operates synchronously with the AD conversion i.e. AD conversion is started by some specific points during the PWM period. In this mode the PWM carrier frequency is fixed.

Regardless of the operating mode the sampling period of the AD has to be fixed. Can anybody give me an advice which MCU is suitable for my application i.e. which DSC is capable to ensure dynamic switching between both the above mentioned modes and also ensure fixed sampling period? Thanks for any ideas.

[xiangjun_rong]

Hi, Stepan,

I think you can use the latest DSC family: MC56F84xxx, MC56F83xxx and MC56F82xxx, all of them can do do your jobs.

AS you know that all of the MC56F84xxx, MC56F83xxx and MC56F82xxx have eFlexPWM module, QuadTimer module, ADC modules. The eFlexPWM module can generate PWM signals, there is a crossbar module, a lot of signals can trigger ADC converter via crossbar module.

For your solution 1, the eFlexPWM module can generate PWM signal, you can use QuadTimer to trigger ADC, in this condition, the ADC conversion and PWM signal frequency are independent.

For solution 2, you can use eFlexPWM to generate PWM signals, and have eFlexPWM generate ADC trigger signal at a PWM specific point, have the trigger signal to trigger ADC, in this condition, the PWM signal frequency and ADC sampling frequency will be the same. For FOC ACIM control, there are three shunt resistors for bottom MOSFET, user can set the ADC triggering point so that the ADC sampling point is at the center of bottom MOSFET turn-on time to sample two ADC channels in parallel so that user can reconstruct 3 phase currents. We have example code for this solution.

Hope it can help you

BR

XiangJun Rong

[stepan_podhorsk]

Hello XiangJun Rong,

thank you very much for your reaction. I need more than one AD conversion per carrier period (at least four) in mode 2 i.e. the eFlexPWM module has to generate more than one ADC trigger signal per carrier period. Is is possible to configure the eFlexPWM in such a manner that it will generate more than one ADC trigger in carrier period? Thanks.

[mohammad_kamil]

Hello Stepan Podhorsky, yes it can convert 4 AD conversion in one PWM cycle, by all the device mentioned by xiangjun.rong. In single PWM trigger you can convert upto 16 ADC channel. As well as you can have multiple ADC trigger from PWM in single PWM period, both is possible from all above device. 

let us know how many ADC channel per PWM trigger you want to convert, and how many ADC trigger you want to have in one PWM period.

With Regards

Kamil

[stepan_podhorsk]

Hello Kamil,

thank you for your answer. I need four ADC triggers in one PWM period. As far as number of ADC channels I need three. Namely stator current in phase U, stator current in phase V and dc bus voltage. Both the stator currents have to be sampled simultaneously. May I ask you for some code example or application note document regarding the ADC and PWM peripherals configuration in above mentioned modes?

[mohammad_kamil · Accepted solution]

Hello Stepan Podhorsky, please visit the nxp.com and MCU pages which is mentioned above you will find code examples of peripherals as well as demo code of motor controls. let me know if you dont find then i will provide you specific link of the same.
Digital Signal Controllers | NXP 

MC56F82xxx | NXP 

Performance Level Digital Signal Controllers, USB FS OTG, CAN-FD | NXP 

MC56F84xxx|Digital Signal Controllers | NXP 

With Regards

Kamil