Hi guys,

Trying to implement a maximum power point tracker (MPPT) in PIC C code. I have attached my code below. The inputs are AN0 to measure voltage of the cell and AN1 to measure the current of the cell, both measure between 0-5V. It is driving the mosfet in a boost converter which is fully working however the problem is that the duty cycle stays at the same value (the initial set value) suggesting the code only runs through once. I am new to programming so any help would be appreciated. I am using a 20MHz oscillator. Also forgot to say im using a thevenin equivalent to replicate the cell at the minute using a 30ohm resistor.

Thanks

#include <p18F258.h>
#include <stdio.h>
 
unsigned int Panel_Power, Panel_Power_Old;
unsigned char Panel_Voltage, Panel_Current, Panel_Voltage_Old, Panel_Current_Old, DUTY = 0x1F, DUTY_MAX = 0xFA, DUTY_MIN = 0x05, FLAG, i;
 
#pragma config WDT = OFF
 
void DELAY(void)
{
    unsigned char a;
    for (a=0; a<1; a++);
}
 
 
void main(void)
{
    CCP1CON = 0;
    PR2 = 0x3F;                 /* Set Time Period Value */
    TRISCbits.TRISC2=0;        /* Set RC2 as an output pin */
    T2CON = 0x00;             /* No Prescalers Timer 2 OFF */
    CCP1CON = 0x0C;         /* PWM Mode */
    CCPR1L = DUTY;                            
    TMR2 = 0;                    /* Reset Timer 2 */
    T2CONbits.TMR2ON = 1;        /* Timer 2 ON */        
    FLAG = 1; /*shows last increment/decrement*/
 
for(i=1; i>0; i++){
Panel_Power_Old = Panel_Power;    /* Set panel power from previous cycle
 
TRISAbits.TRISA0 = 1;             /* AN0 analog input for voltage*/
ADCON0 = 0x81;                 /* 10000001 */
ADCON1 = 0x44;                    /* 01000100*/
DELAY();                    /* Gives ADC time to sample*/                    ADCON0bits.GO = 1;                        /* Begin A/D Conversion*/
    while(ADCON0bits.DONE == 0);            /* Wait for the conversion to end*/
    Panel_Voltage = ADRESH;                    /* Save voltage in ADRESH as Voltage_Step_Number*/
 
    TRISAbits.TRISA1 = 1;                     /* AN1 analog input for current*/
    ADCON0 = 0x89;                             /* 10001001 1st 2 bits fosc/64 along with ADCON1, next 3 select channel AN1, last digit turns ADC on */
    ADCON1 = 0x44;                            /* 01000100 Left justify, fosc/64, 3 analog inputs, Vref+ = VDD, Vref- = VSS */
    DELAY();                                /* Gives ADC time to sample*/                    
    ADCON0bits.GO = 1;                        /* Begin A/D Conversion*/
    while(ADCON0bits.DONE == 0);            /* Wait for the conversion to end*/
    Panel_Current = ADRESH;                    /* Save current in ADRESH as Panel_Current*/
 
    Panel_Power = Panel_Voltage * Panel_Current;
 
    if(FLAG == 1){                                        /* Compare Voltage and power to previous and increment/decrement DUTY cycle*/
        if(Panel_Power - Panel_Power_Old > 0){    
        DUTY++;
        FLAG = 1;
        }
        else{
        DUTY--;
        FLAG = 0;
            }
    }
 
    if(FLAG == 0){
        if(Panel_Power - Panel_Power_Old > 0){
        DUTY--;
        FLAG = 0;
        }
        else{
        DUTY++;
        FLAG = 1;
            }
    }
 
 
    if(DUTY > DUTY_MAX){                /* Keeps DC between 0 and 95% */
        DUTY = DUTY_MAX;    
    }
    if(DUTY < DUTY_MIN){
        DUTY = DUTY_MIN;
    }    
 
 
    PIR1bits.TMR2IF = 0;                    /* clear timer 2 flag*/
    while(PIR1bits.TMR2IF==0);                /* wait for end of period*/
 
}    
}

 

rednwhite,
i am also implementing mppt but with buck-boost converter. It will be very helpful to me if you upload your implemented mppt details.
Regards