Greetings,

I am working in a project that I need to develop a SPWM Inverter for an induction motor or an UPS.

Few days ago, I started to develop a small program that uses a sine lookup table and the PWM peripheral to generate the SPWM pulses in the PWML1 and PWMH1 pins of an dsPIC33FJ32MC202.

The sine lookup table comparison are not yet implemented. I am currently using this code to just test the PWM pins of the dsPIC.

However, when I simulated my code in the Proteus ISIS nothing happens and unfortunately I am quite new to the dsPICs. Here is my current code.

#include <p33FJ32MC202.h>

_FOSCSEL(FNOSC_FRCPLL)                // configures the fast oscillator with PLL
_FOSC(FCKSM_CSECMD & OSCIOFNC_ON)    // enables only clock switching and digital I/O
_FWDT(FWDTEN_OFF)                    // disables the watchdog timer
_FPOR(FPWRT_PWR1)                    // disables the power on reset 
_FICD(ICS_PGD2 & JTAGEN_OFF)        // disables the JTAG and the ICS

#define OC5_IO    22            // define OC5 output function number for PPS

unsigned char sine[42]={0,9,19,28,38,47,57,66,75,84,93,102,111,120,128,136,144,152,160,167,174,181,188,194,200,206,211,217,221,226,230,234,238,241,244,246,249,251,252,253,254,254};
unsigned char pwmFHtimes;    // PWM frequency hopping times, it is based on PWM cycle

void MCU_init(void)
{
    TRISB=0x00;                // PORT B as output
    RCONbits.SWDTEN=0;        // Disable Watch Dog Timer
    pwmFHtimes=0;
    OC1CONbits.OCM=0;         // Output compare channel is disabled
    OC1R= 0x0099;            // Initialize Compare Register1 with 50% duty cycle
    OC1RS= 0x0099;            // Initialize Secondary Compare Register1 with 50% duty cycle
    OC1CONbits.OCSIDL= 0;    // Output capture will continue to operate in CPU Idle mode
    OC1CONbits.OCFLT= 0;    // No PWM Fault condition has occurred (this bit is only used when OCM<2:0> = 111)
    OC1CONbits.OCTSEL= 0;    // Timer2 is the clock source for output Compare
    OC1CONbits.OCM= 0x6;    // PWM mode on OC, Fault pin disabled
    PR2= 0x0132;            // Initialize PR2 with 0x0132 = 0d306 as PWM cycle
    IFS0bits.T2IF=0;        // Clear Output Compare interrupt flag
    IEC0bits.T2IE=1;        // Enable Output Compare interrupts
    T2CONbits.TON=1;        // Start Timer2 with assumed settings
}

int main (void)
{
    while(1)
    {
        Idle();
    }
    return 0;
}

void __attribute__ ((__interrupt__, no_auto_psv)) _T2Interrupt(void)
{
    IFS0bits.T2IF = 0;
    
    if (++pwmFHtimes == 5) 
    {    
        // every 5 cycles for update
        pwmFHtimes = 0;
        // update the duty cycle for PWM
        if (OC1RS == 0x0099)
        {
            OC1RS = 0x00E5;    // 75% duty cycle
        }
        else
        {
            OC1RS = 0x0099;    // 50% duty cycle
        }
    }
}

Any ideas what is wrong, please? The PWMH1 and PWML2 pins should be pulsing...

Thanks,
FBorges22

 

If your going to use the inverter to run a motor. What your trying to do is usually done by comparing a sine wave with a triangle wave. the result is then used to switch a pair of mosfets or IGBT's, one for the positive going and one for the negative going current. It will only approximate a sine wave. This is done because the switching devices can't make a true sine wave and live.