# A Comparative Study of Storage Batteries for Electrical Energy Produced by Photovoltaic Panels
## 2 Materials and Methods  
### Model in MATLAB-Simulink for Controlling Electric Energy Storage in Batteries  
#### 2.1.1 Description of Model Developed in MATLAB-Simulink Programming Environment  
A diagram of the model developed in the MATLAB-Simulink programming environment for controlling energy storage in batteries is presented in Figure 1 below.  
This model is composed of the following components: a photovoltaic module; a DC-DC step-down buck-type convertor; a control subsystem for the buck convertor based on the MPPT algorithm for incremental conductance; a power electronic circuit for controlling battery charging and discharging; a control block of transistors for the power electronic circuit; a measuring block for the parameters of the photovoltaic panels; and a measuring block for the parameters of the battery for storing the electrical energy produced by the photovoltaic panels. The photovoltaic module is composed of two photovoltaic panels connected in parallel, of the type Soltech 1 STH-230P. The technical characteristics of the photovoltaic panel are \(P_{max}=228.73\) W and \(U_{max}=37.1\) V. From Figure 2, the values of the photovoltaic system at the maximum power point for an incident solar radiation intensity of 1000 W/m\({}^{2}\) at a temperature of 25 \({}^{\circ}\)C can be deduced as follows: \(U_{max}=29.9\) V,\(P_{max}=457.5\) W. The parameters of the buck-type DC-DC convertor are presented in ref. [26]. For the control of the photovoltaic panels, a diagram of the variation in solar radiation intensity during a time interval of 40 s is presented in Figure 3. The environment in which the photovoltaic panels were running was kept at a constant temperature of 25 \({}^{\circ}\)C. The values of solar radiation go in an upward direction and then in a downward direction, representing the battery's discharging and charging modes.  
Figure 1: Model in MATLAB-Simulink for battery control system.  
Figure 2: Characteristics of photovoltaic module.  
A diagram of the control subsystem of the DC-DC buck-type convertor based on the MPPT algorithm for incremental conductance is illustrated in Figure 4. The power electronic circuit for controlling the battery's charging and discharging modes is composed of two IGBT-type field-effect power transistors. This circuit is connected to the output terminals of the DC-DC buck-type convertor by means of an RC series-type filter circuit. The control block of the transistors is presented in Figure 1. It is composed of two proportional-integrative-type (PI_b and PI_b1) controllers and a signal-generating block, PWM. The measurement blocks for the photovoltaic panel parameters and battery parameters are represented in Figure 1 by the oscilloscopes PV1 and PV2.  
For the photovoltaic panels, the oscilloscope PV1 measures their voltage variation, as well as the variation in their current intensity and electric power as a function of the variation in solar radiation during a time interval of 40 s. Meanwhile, the oscilloscope PV2 measures the charging status of the battery (SOC), as well as the variation in its current  
Figure 4: Diagram of control subsystem of DC-DC buck-type convertor.  
Figure 3: Variation in solar intensity.  
intensity and voltage as a function of the variation in solar radiation during a time interval of 40 s.