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124 CHAPTER 4 Performance of MPPT Techniques of Photovoltaic Systems

technique imposed a complexity especially with online systems like MPPT of PV
system.
The main problem in the real operation of PSO is the use of random values on the
PV system, which can affect the stability of the system. Also, the main concern in
using PSO technique in MPPT of PV system is to have lower number of particles
to achieve consistent solution. Using conventional PSO will not achieve this require-
ment as fast as required. So, fast technique to get optimum duty change will be help-
ful in increasing the stability of the PV system. A modified PSO (MPSO) technique
[50,55] has been used to modify the inertia weight, u using genetic algorithm prin-
cipals. The modified inertia weight u can be obtained from the following equation,
which increases the value of inertia weight u for the beginning and reduce it for pre-
cise increment at the end of optimization.

uðkÞ¼ u s ðu s u e ÞðT m kÞ=T m (4.6)

where u s is the initial inertia weight, u e is the inertia weight when reaching
maximum inertia times, and T m is the maximum inertia times.

2. PV SYSTEM UNDER NONSHADING CONDITIONS

2.1 SIMULATION OF PV SYSTEM
The proposed system has been simulated using a Simulink that comes with Matlab
software package. In the proposed system, the simulation has been carried out using
three different techniques for comparison. In the first technique, a Matlab file has
been used to calculate the theoretical MPP of the power curve. In the second tech-
nique, a constant terminal voltage of the PV is introduced. This voltage is chosen to
be the constant voltage that corresponds to the highest possible output power in the
normal operating range. In the last technique, an FLC has been used to track the
MPP. The simulation model of the proposed system using Matlab/Simulink program
is shown in Fig. 4.6. The simulation of the proposed system contains submodels that
can be explained in the following sections.

2.1.1 Photovoltaic Cell Model
PV cell is a pen junction that can absorb photons in the light to generate electric
power by the so-called PV effect. The generated power depends on the radiation
level of the sunlight, temperature, and the terminal voltage of PV cell. Several kinds
of materials have been used to fabricate the PV cells, which differ in their charac-
teristics from one type to another. Crystalline silicon PV cells are the most widely
used [56]. Crystalline silicon PV cells have been used for a long time and it became
mature technology. Its price became lower and lower especially with mass-fraction
production. For this reason, this kind of PV cells will be considered in this paper.
Other kind of PV cells have the same analysis but with different performance
characteristics.