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MATLAB Implementation of PO MPPT algorithm for Solar PV System (Part 2)

This video present about P&O maximum power point tracking algorithm for a solar PV system and how it implemented in MATLAB.

In this work, perturb and observe maximum power point tracking controllers are utilized to extract the maximum power from the solar PV panel. The P&O algorithms operate by periodically perturbing i.e. incrementing or decrementing the array terminal voltage or current and comparing the PV output power with that of the previous perturbation cycle. If the PV array operating voltage changes and power increases dP/dV greater than 0, the control system moves the PV array operating point in that direction; otherwise, the operating point is moved in the opposite direction. In the next perturbation cycle, the algorithm continues in the same way.

A common problem in PO algorithms is that the array terminal voltage is perturbed every MPPT cycle; therefore when the MPP is reached, the output power oscillates around the maximum, resulting in power loss in the PV system. Perturb & Observe is the simplest method and is widely used. In this technique we generally use two sensors, that is the voltage sensor, to sense the PV module voltage and current sensor to sense the PV current and hence the cost of implementation is less and hence easy to implement without any complexity. In certain situations like changing atmospheric conditions and change in irradiance the maximum power point shifts from its normal operating point on the PV curve. In the next iteration, it changes its direction and goes away from the maximum power point and results in multiple local maxima at the same point. So the maximum power point deviates from its original position.

Algorithm for Perturb and Observe Technique:

a. Read the value of current and voltage from the solar PV module.

b. Power is calculated from the measured voltage and current.

c. The value of voltage and power at kth instant are stored.

d. Then next values at k+1th instant are measured again and power is calculated from the measured values.

e. The power and voltage at k+1th instant are subtracted with the values from kth instant.

f. In the power voltage curve of the solar PV module,

it is inferred that in the right-hand side curve where the voltage is almost constant and the slope of power voltage is negative dP/dV less than 0 whereas on the left-hand side, the slope is positive dP/dV greater than 0. Therefore the right side of the curve is for the lower duty cycle nearer to zero whereas the left side curve is for the higher duty cycle nearer to unity. g. Depending on the sign of dP i.e. P k+1 – P k and dV i.e. V k+1 –V k after subtraction the algorithm decides whether to increase the duty cycle or to reduce the duty cycle.

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