The perturb and observe MPPT can track the power fast if the step increment (Delta V in Fig. 1) in the operating point is increased. Although, it will enhance the dynamic response of the MPPT but it will also increase the power oscillations around the MPP. To solve this issue of power oscillations, the step size in each perturbation can be reduced at the cost of slow tracking speed. Therefore the choice of perturbation size needs proper optimization.

Fig. 1 Basic Perturb and Observe MPPT algorithm

Fig 2.Power Oscillations can be seen in the top graph. Voltage oscillations in bottom graph.

Another important issue is the sampling rate. The sampling means how often the system measures the power. It is necessary in order to deal with the dynamics of the power electronic converter. The transient needs time to settle down which is provided by the sampling rate. If the sampling rate is too high (means very less time in between each sample) it may lead the system in unstable mode because the maximum power can be missed in between each sampling interval.It is recommended to use a sampling time as small as possible without driving the system in unstable region of operation.

Regarding the system stability the steady state performance can be enhanced by using large inductance. Because the large inductance will smooth the current and switching losses. However, the larger the inductance the slower is the dynamic response. One way to optimize the performance in steady as well as dynamic condition is to use coupled inductance. The use of two parallel inductance coupled together can provide different equivalent inductance which makes it possible to get good steady and dynamic performance at the same time [1].

Reference:

[1]Veerachary, M.; Senjyu, T.; Uezato, K., "Neural-network-based maximum-power-point tracking of coupled-inductor interleaved-boost-converter-supplied PV system using fuzzy controller," Industrial Electronics, IEEE Transactions on , vol.50, no.4, pp.749,758, Aug. 2003