## 2 Modelling of PV System's Components
### Modelling of Photovoltaic Panel  
The accuracy of a PV model has a great significance on system design. To predict the energy output of the system, researchers have to investigate meteorological condition at system's location. It is because the performance of PV modules strongly depends on the sun light condition and cell temperature. Moreover, the energy generated also depends on components' rated characteristics, installation configuration, and surroundings' condition [7]. PV power generated from a PV panel is highly affected by total of solar radiation received. Solar radiation data provides information on how much energy strikes the specific earth location [15]. However, solar radiation value is different if the panel slanted at different angles and orientations. Solar radiation data often measured in horizontal plane without any obstacle or shading effect. However, in some situations, when PV panels are mounted in tilted position, such as in building integrated photovoltaic system application, the total radiation input for the tilted PV modules has to be calculated [3]. Following this, [PERSON] et al. reviewed solar energy modelling techniques in [15]. The authors presented linear, nonlinear and artificial intelligence approach models for both global and diffused solar energy model on horizontal PV panel. The direct solar radiation comes directly from the sun. Meanwhile, diffuse solar radiation scattered from dome of the sky without direction. However, for a tilted PV panel, solar radiation comprises direct portion, diffuse portion and reflected portion [15; 16; 17]. To model diffused radiation on a tilt surface, isotropic and anisotropic models can be used [15]. According to [18], the isotropic model assumes the intensity of sky-diffused radiation is uniform over the sky dome. Hence, the diffuse radiation incident on a tilted PV module depends on the fraction of the sky dome seen by it. The second model is the anisotropic model, where it assumes the anisotropy of sky diffused radiation in circumsolar region and isotropic distributed diffuse component from the rest of sky dome. The output power of a PV system is accessed via voltage and current produced from PV module where the multiplication of voltage and current produces power [19]. However, it is important to analyze power estimation accuracy, since the actual power output is usually lower than modelled one [5]. In [20], the author reviewed methods to calculate annual photovoltaic generation, by sorting all of the proposed methods into three categories. In the first method, the authors construct an I-V curve by using atmospheric parameter value, and power generated was calculated from it. Meanwhile, in the second method the power is directly calculated using time series atmospheric parameter values. On the other hand, the last method employs some technical factors such as performance ratio and system efficiency in calculating the power generated from a PV panel/array. In [1], the authors conduct a simple review on classical and novel modelling techniques applied for various types of photovoltaic systems such as meteorological data forecasting using artificial intelligence techniques. In general, two circuit diagrams can represent PV cell model namely single-diode and two-diode models. Single diode model is one of the most commonly used PV generator's models. Both models are based on the fact that the solar cell is an illuminated p-n junction in the reverse-bias, connected to a resistive load. From [21], a solar cell can be represented using an equivalent circuit diagram consisted of a dependent current source connected on parallel with diode in the reverse mode. These two components are also connected in parallel with a relatively large resistor to represent the dark current of this p-n junction.