6 HPWM signal generation with PIC18F4431

[HenrikOlsson]

Hi,
I'm not using a simulator, I just sent the values to the PC and plotted them with EXCEL. Here's the exact code I used to test with:

DEFINE LOADER_USED 1
DEFINE OSC 20
DEFINE HSER_BAUD 19200
 
i VAR BYTE
T VAR BYTE
uDuty VAR WORD
vDuty VAR WORD
wDuty VAR WORD
 
Main:
For i = 0 to 2   'Make three periods
  T=0
    
   for T=0 to 255
   ' PWM U phase calculation
   uduty=((sin(t)+128)*4)  
      
   ' PWM V phase calculation
   vduty=((sin(t+85)+128)*4)
    
   ' PWM W phase calculation
   wduty=((sin(t+170)+128)*4)
   
   HSEROUT [DEC uDUTY, ",", dec vDUTY, ",", dec wDUTY, 13]
  next
NEXT
WereDone:
Goto WereDone

Try removing C3, C6 and C8 to start with.

[pxidr84]

Hi,
I'm not using a simulator, I just sent the values to the PC and plotted them with EXCEL. Here's the exact code I used to test with:

DEFINE LOADER_USED 1
DEFINE OSC 20
DEFINE HSER_BAUD 19200
 
i VAR BYTE
T VAR BYTE
uDuty VAR WORD
vDuty VAR WORD
wDuty VAR WORD
 
Main:
For i = 0 to 2   'Make three periods
  T=0
    
   for T=0 to 255
   ' PWM U phase calculation
   uduty=((sin(t)+128)*4)  
      
   ' PWM V phase calculation
   vduty=((sin(t+85)+128)*4)
    
   ' PWM W phase calculation
   wduty=((sin(t+170)+128)*4)
   
   HSEROUT [DEC uDUTY, ",", dec vDUTY, ",", dec wDUTY, 13]
  next
NEXT
WereDone:
Goto WereDone

Try removing C3, C6 and C8 to start with.

In reality, I think that my RC filter in Proteus is bad.

If I watch the raw PWM outputs, it seems perfectly good (with correct phase angles and duty cycles). However, in extreme duty (like 0 or 1023), the PWM "jumps" (like before, I think it's a sim issue, I will try the PIC in the real life with an oscilloscope).

In other words, my code is working quite well now, thanks for the "**", I didn't know this operator before, until now.

[HenrikOlsson]

Hi,
Like I said in an earlier post, I think it is the dead-time insertion that makes the waveform "jump" at the extreme ends. Do try it with real hardware and let us know how it goes. Just remember that if you low-pass filter the PWM to watch it on a scope might not see any artifacts introduced by the deadtime insertion - if indeed that is what's causing it. So make sure you watch the "raw" PWM signals as well in order to see if it behaves as in the simulator.

As a simple test, try removing the deadtime insertion from the code and see if it still looks strange in the simulator.

/Henrik.

[pxidr84]

Hi,
Like I said in an earlier post, I think it is the dead-time insertion that makes the waveform "jump" at the extreme ends. Do try it with real hardware and let us know how it goes. Just remember that if you low-pass filter the PWM to watch it on a scope might not see any artifacts introduced by the deadtime insertion - if indeed that is what's causing it. So make sure you watch the "raw" PWM signals as well in order to see if it behaves as in the simulator.

As a simple test, try removing the deadtime insertion from the code and see if it still looks strange in the simulator.

/Henrik.

Yes, of course I've readed your post above. I've modified the code (add +3 to the end of each line), now the PWM signal doesn't "jump" anymore.
However, if I remove the deadtime or even modify it, the jumpy PWM remains.

Now signals are better, but sine are not perfect for the highest frequencies, I think that my low-pass filter hasn't good R and C values (1k and 1000nF).

[senertek]

hi ,
I have already developped many ac inverters range 0.75 kw to 915 kw..with . I seen this thread ..it s very good..to see picbasic projects in this field....
Designing one 3 phase ac inverter is not easy project...you must know many kind of points about high voltage igbt , drivers , dcbus topologys ,emc ,emi , multi tasking etc...(it take many years)
If you want , I can help for your project..
I can try your codes with my high voltage kits , igbt driver modules ...and inform you ..codes works or not...

savas

[pxidr84]

hi ,
I have already developped many ac inverters range 0.75 kw to 915 kw..with . I seen this thread ..it s very good..to see picbasic projects in this field....
Designing one 3 phase ac inverter is not easy project...you must know many kind of points about high voltage igbt , drivers , dcbus topologys ,emc ,emi , multi tasking etc...(it take many years)
If you want , I can help for your project..
I can try your codes with my high voltage kits , igbt driver modules ...and inform you ..codes works or not...

savas

Thanks.

Well, I'm doing studies in electrical engineering, so I've a litte knowledge about this.
I'm using an intelligent IGBT module from STMicroelectronics, the STGIPS20K60 (datasheet : http://www.st.com/internet/com/TECHN...CD00244265.pdf).

No drivers needed (they're integrated), just optocouplers.

[pxidr84]

Ok, a little update.

I've tested the program on the real PIC with an oscilloscope. All of the output signals are correct, but the sine cycle is very slow (about 4 seconds to make a complete sine period, so f=1/4=0,25Hz).
The PWM frequency seems correct (3,245kHz).
I've defined correctly the configuration fuses (or bits), with "HS oscillator" setting, because I'm using a 40MHz quartz oscillator connected to OSC1/OSC2 pins with 22pF ceramic capacitors.

The code (note I'm not using the FOR... NEXT loop in this case, like the upper programs, it's a lot faster if I use the FOR... NEXT loop, but I don't know why) :

'PIC initialization
DEFINE OSC 40      
DEFINE LCD_EREG PORTD
DEFINE LCD_DREG PORTD
DEFINE LCD_EBIT 0
DEFINE LCD_RSBIT 1


'DT interrupt system include
INCLUDE "DT_INTS-18.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"  ' Include if using PBP interrupts


'Port registers configuration
PORTB=%0          ' Clear ports
TRISB=%11000000   ' PWM 0,1,2,3,4,5 outputs

                            
'PCPWM registers configuration
DTCON=%110        ' Deadtime (600ns)
PTCON0=%100       ' 1:1 postscale, Fosc/4 1:1 prescale, free running mode
PTCON1=%10000000  ' PWM time base is ON, counts up, 19.45kHz/4
PTPERL=%0         ' PWM low-side
PTPERH=%1         ' PWM high-side

	
'PWM registers configuration
PWMCON0=%1000000  'PWM 0,1,2,3,4,5 set in pair mode
PWMCON1=%1        'PWM timer sync configuration


'Interrupt processor
ASM
INT_LIST  macro    ; IntSource, Label, Type, ResetFlag
        INT_Handler   TMR1_INT,  _pwmint,   PBP,  yes
    endm
    INT_CREATE     ; Creates the interrupt processor
ENDASM


'Timer configuration
T1CON=%10000001            ; Prescaler = 1:8, TMR1ON, 16-bit counter
@ INT_ENABLE  TMR1_INT     ; Enable Timer 1 interrupts


'PWM calculation variables
uduty VAR WORD     'U phase duty
vduty VAR WORD     'V phase duty
wduty VAR WORD     'W phase duty
dutydiv var WORD   'Frequency diviser
dutymul VAR WORD   'Duty multiplier
t VAR byte         'Incremental value


'Variables definition
dutydiv=0       'Range : 0-65535
dutymul=65535   'Range : 0-65535 (for exemple, 32767=0.5)
t=%0            'T initial value


'Main program loop
mainlp:

HIGH PORTA.0
pause 100
LOW PORTA.0
pause 100

goto mainlp


'PWM calculation and update interrupt
pwmint:

    'Frequency diviser
    pauseus dutydiv

    'PWM U, V, W phases calculation
    uduty=(((sin(t)+%01111111)*%100)**dutymul)+%100
    vduty=(((sin(t+%01010101)+%01111111)*%100)**dutymul)+%100
    wduty=(((sin(t+%10101010)+%01111111)*%100)**dutymul)+%100

    'PWM U phase update
    PDC0L=uduty.LOWbyte
    PDC0H=uduty.HIGHByte

    'PWM V phase update
    PDC1L=vduty.LOWbyte
    PDC1H=vduty.HIGHByte

    'PWM W phase update
    PDC2L=wduty.LOWbyte
    PDC2H=wduty.HIGHByte
    
    'T variable verification and incrementation
    if t<%11111111 then 
    t=t+%1
    else 
    t=%0 
    endif

@ INT_RETURN

I think it's a TIMER problem (TMR1 is at 32kHz, isn't it?)