The set of photovoltaic modules is called photovoltaic or solar panel or an array. The photovoltaic modules that create an array can be connected to each other in series, parallel or Mixed, to obtain the voltage required by the system. This makes photovoltaic systems to be able to suit any installation, large or small. The type of power they provide is direct current (DC), so if we need alternating current (AC) or increase the voltage, it will have to be added an inverter or a power converter. For the installation of these panels it should be taken several considerations. First of all, it is to be noted that throughout the year, the angle of sunlight varies, and we must ensure that the direction of the light vector is parallel to normal vector of the panels. At the installation time, In addition, the panels must be installed with a minimum distance from any area of approximately 5 cm to permit an adequate airflow through the bottom, which prevents overheating that could reduce their performance. Another factor that might reduce its performance is dirt, since it makes difficult the incidence of sunlight.

An equivalent circuit refers to a theoretical circuit that retains all of the electrical characteristics of a given circuit. More complex circuits are often called macro models of the original circuit.

The equivalent circuit is shown in Figure 1 depicted.

where R_s is the array series resistance, R_p is the array parallel resistance, N_s and Np are the number of series and parallel modules respectively, I and V are the output current and voltage of the array and Im is the module current and can be obtained from the following equation:

I M = I P V N P − I O N P [ exp [ v + r ( N S N P ) I V S N S ] − I ] [4]

where, a is the diode ideality constant, V_t is the thermal voltage of the array and can be obtained from the equation:

V t = N c s K T Q [5]

N_cs is the number of cells connected in series, q is the electron charge, k is Boltzmann’s constant and T is the temperature of the P-N junction in Kelvin’s. I_pv is the photovoltaic current and can be expressed by:

I P V ( I P V N + K I Δ T ) G G N [6]

And I_o is the reverse leakage current of the diode and can be calculated from:

where: I_pvn is the generated current at 25˚C and 1000 W/m² (nominal conditions), K_i, K_v the current and voltage temperature confidents respectively, G is the irradiance and G_n is the irradiance at nominal conditions, I_scn, V_ocn are the short circuit current and open circuit voltage respectively at nominal conditions and T is the difference between the actual and the nominal temperatures in Kelvin’s.

I O = I c s + K i Δ T E X P ( V O C N + K v Δ T a v t ) − 1 [7]

Maximum power point trackers are a form of DC-DC converter. It uses electronic components to adjust PV outputs and make it operate at its maximum power point under changing irradiance and temperature. Interactive inverters often contain MPPT circuits. For large PV system with multiple PV arrays, individual MPPTs are designed to connect each array, in this way it is more efficient for MPPTs to operate at maximum output with each array that has different characteristics. So the total performance of PV system improves. Maximum power point of any PV varies with the variation of the atmospheric conditions (solar irradiance and temperature). This means that there is always one optimum terminal voltage for the PV array to operate at with each condition as shown in the Figuredepicted below to obtain the maximum power output. In our paper we applied the perturb & observe (P&O) method to extract that point (Figure2).

The voltage we that have generated using the PV panel, in order to connect it to the Grid we have to increase the magnitude of the voltage, Which can be done with the use of a DC-DC converter, for our purpose we have chosen Boost converter which will help us to increase the level of voltage that we have generated (Figure 3).

Irradiance is the amount of light energy from one thing hitting a square meter of another each second. Photons that carry this energy have wavelengths from energetic X-rays and gamma rays to visible light to the infrared and radio. We can estimate the total radiated power of the sun with the law of Stefan and Boltzmann.

P = 4 π r 2 σ ε T 4 = 3.9 × 10 26 W

where T is the temperature (about 5800 K), r is the radius of the sun (6.9 × 10⁸ m) and σ the Boltzmann constant (5.67 × 10⁻⁸ W/m²K⁴) and ε is the emissivity of the surface (Figure 4).

In order to define the photovoltaic plant situation object of this thesis report, it is necessary to start showing the radiation that reaches the plant. Here, we work in rangpur district due to its geographical situation, the photovoltaic modules are oriented towards the south with 2 axis direction for maximum benefit of solar irradiation (Figure 5).

By using this data we draw a virtual diagram for proposed area.

Represents the railway line.

Represents a typical tree beside the railway line.

• Represents the PV module mounted on the railway line.

For the PV system designed for Rangpur district, we have chosen for simulation is SAM (system Advisor Model) software. SAM has several built-in mathematical models for component such as photovoltaic module, inverter and other required tools. SAM gives various types of designing options such as residential, commercial, single owner etc. Using these options there are various kinds of system can be developed for desired PV plant. Firstly we have done some small design to gain primary knowledge and after that we designed a project of grid connected system. Here we have defined our location, orientation, and horizon. For location choosing, we have selected Rangpur in Bangladesh. Since we want to develop a PV system, so we have to choose a module and an inverter, defined our monthly energy consumption rates and declared our planned power. The parameters are given below.