MPPT charge controller techniques

MPPT charge controller techniques,Solar panels exhibit non-linear current-voltage characteristics that varies with the environmental changes which makes it harder to optimize the solar power generation during constant variation in light levels, temperature and other solar panel characteristics. This is where the different MPPT techniques comes into play. The main idea behind MPPT is to achieve such operating voltages of the solar panel that are close to the maximum power point under changing environmental conditions.

There are several MPPT techniquesfor a PV system which include Fuzzy Logic Control, Neural Network, Fractional open circuit voltage, Fractional short circuit current and so on. But the two most commonly used techniques are mentioned below:

• Perturb and Observe (P&O-also known as thehill climbing method)
• Incremental Conductance (InCond)

Although both techniques have their merits and demerits like all the other MPPT techniques does, but the main advantage of these two is their simplicity and ease of implementation.

 

In this method, the voltage and the current of the solar panel are measured to begin with and hence the corresponding power ’Pi’ is calculated. The operating voltage of the panel is then perturbed (∆V) and the resulting power ‘Pj’ is compared with the previously calculated power ‘Pi’. The difference of the two, determines the direction of further required changes in the current and voltage values.

If the difference between the two power values is positive i.e. ‘Pj’ is greater than ‘Pi’, the perturbation is considered to be in the correct direction and therefore the voltage and current iskept on changing in the same direction until the power starts to decrease. On the other hand, if this differenceresults in a negative value, then the next perturbation should be in the opposite direction. This process continues until the maximum power point is reached.

The main disadvantages of P&O method is that at a steady state, the algorithm is unable to realize that it has actually attained the maximum power. Instead,the operating point starts to oscillate around the maximum power point. Also it is observed that under rapid changing atmospheric conditions, the algorithm may end-up perturbing in the wrong direction.

INCREMENTAL CONDUCTANCE

In this algorithm, the maximum power point is determined by comparing two entities, instantaneous conductance (I/V) and incremental inductance (∆I/∆V). The algorithm takes advantage of the fact that at MPP, the slope of power-voltage curve is zero.

It overcomes one of the major drawbacks of Perturb and Observe i.e.instead of oscillating, the incremental conductance can determine when it has actually reached the maximum power point. Once that point is reached, the system is maintained at this instant unless the current (I) changes. The algorithm, then, increments or decrements the operating voltage to reach the maximum power point.Incremental conductance can also deal with the rapid climate changes in an efficient manner as compared to P&O.The disadvantage,however, is that it requires complex circuitry.

There are many other techniques also developed for maximum power point tracking. I have mentioned most popular method.In next article I will post circuit diagram of MPPT charge controller. Keep visiting our website for more information related to MPPT charge controller 🙂