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I'm currently researching on MPPT (Maximum Power Point Tracking) and will do some programming into arduino using this flowchart but right now i'm struck on this as I do not understand what is \$\textrm{PV_P} (n)\$ and \$\textrm{PV_P}(n-1)\$.

I have no idea what is the \$n\$ despite searching online for all sort of explainations, most of the answer I found is them explaining about the terms etc. Appreciate any efforts of letting me know about the meaning for the \$n\$ and briefly about the flowchart.

enter image description here

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  • \$\begingroup\$ "n" is probably the current time step, so PV_P(n) is "The value of PV_P at time n" \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Nov 1, 2016 at 6:03
  • \$\begingroup\$ immibis has it nailed. It's the only possible rational interpretation. Plus, that huge programming block at the bottom of the page absolutely confirms the idea. They simply copy the entire current state, making the old prior state equal to the current state, so that you can read in the next vector. What other interpretation could be possible, given that? \$\endgroup\$
    – jonk
    Commented Nov 1, 2016 at 6:24
  • \$\begingroup\$ Thanks for the reply! I see, so 'n' is the current time step, appreciated the reply, going to research more about it,going to take awhile for me to digest everything.. Have a good day :) \$\endgroup\$
    – Lyber
    Commented Nov 1, 2016 at 7:02

1 Answer 1

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The MPPT algorithm that is implemented in your flow chart is the typical known as "Hill Climbing" or P&O (Perturb and Observe) .

It consists basically of the following (more or less)

  1. Start at Duty cycle 0:
    • no current is being consumed, PV_V = Open circuit voltage.
  2. increase the duty cycle which perturbs the PV current and consequently the PV voltage.
  3. Calculate the current power PV_P(n) in your case
  4. Compare the current power to the previously generated power PV_P(n-1) in your case
    • If the power is higher I am going in the right direction ---> keep increasing PWM
    • Goto 3.
    • If not, change direction --> decrease the duty cycle, Goto 5.
  5. Calculate the current power
  6. Compare the current power to the previously generated power
    • If the power is higher I am going in the right direction ---> keep decreasing PWM
    • Goto 5.
    • If not, change direction --> increase the duty cycle, Goto 3.

Here is a small animation showing how it works:

MPPT P&O algorithm demo

notice how your step size and the step frequency will define the tracking precision , stability, speed,...

Cheers

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  • \$\begingroup\$ for Number 4, "Compare the current power to the previously generated power PV_P(n-1) in your case" Do you mean that first, i will calculate power then increase (calculate the new power again) then compare both of the value? \$\endgroup\$
    – Lyber
    Commented Nov 4, 2016 at 4:46
  • \$\begingroup\$ @Lyber : yes. PV_P(n) is what you calculate "now", and PV_P(n-1) is what you calculated before. Whenever you change (increase or decrease) your PWM : PV_P(n-1) = PV_P(n) , and you calculate a new PV_P(n). \$\endgroup\$
    – Pau Coma Ramirez
    Commented Nov 4, 2016 at 9:09

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