UM1561 datasheet(33/39 Pages) STMICROELECTRONICS

33 / 39 page

UM1561

MPPT - maximum power point algorithm

Doc ID 023556 Rev 1

33/39

MPPT - maximum power point algorithm

The overall control architecture for the input side of the power converter requires three

feedback signals for correct operation, input panel current and input panel voltage are used

for maximum power point tracking; the output bus voltage is used for monitoring the OV

condition and to control the starting/stopping procedure.

These signals are sent to the ADC inputs of the microcontroller, according to the pin

assignment, and in function of these values, two timers generate PWM output to drive the

DC-DC Power MOSFETs or disable the driving signals to turn off the module, isolating the

solar panel from the output bus. The duty cycle value is regulated by a maximum power

point tracking algorithm embedded in the STM32F1xx microcontroller.

This algorithm is developed inside the MPPT_func(). Starting from I/O information

(PV_voltage and PV_current), the DC power is calculated and in function of the PV_voltage,

it regulates the duty cycle value of the two PWM timers.

void MPPT_func()

{

CCR_Val = (u16) DCDC_GetDutyCycle();

Vpanel=PV_Voltage;

Ipanel=PV_Current;

if(Ipanel==0) Ipanel=1;

Pow = (u32)((u32)Vpanel * (u32)Ipanel);

if(flag_mppt==1) { Step_modify(); }

if((Pow >= Powprev) && (Vpanel <= Vpanel_prev))

{

if((CCR_Val - CCR_Val_step)<=235)

{

CCR_Val=235;

DCDC_SetDutyCycle((u16)CCR_Val);

}

else

{

CCR_Val=CCR_Val - CCR_Val_step;

DCDC_SetDutyCycle((u16)CCR_Val);

}

if((Pow > Powprev) && (Vpanel > Vpanel_prev))

{

if((CCR_Val + CCR_Val_step)>=512)

{

CCR_Val=512;

DCDC_SetDutyCycle((u16)CCR_Val);

}

else

{

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