Control of a Photovoltaic System Operating at Maximum Power Point and Constant Output Voltage under Different Atmospheric Conditions

This paper focuses on the design, modelling and MATLAB simulation of photovoltaic (PV) panel, DC/DC converters, Maximum Power Point Tracker (MPPT), battery, PID controllers and other control algorithms for constant DC voltage output PV system. Overall system is modelled and simulated with MATLAB/Simulink-SimPowerSystems toolbox which is specifically developed to simulate electrical power systems. Commonly used conventional linearization methods are not available for PID controller design for such a system having cascaded pulse width modulation (PWM) switching DC/DC converters causing high nonlinearity, forcing the use of a new alternative technique based on simulated input/output data. PV system is simulated under different atmospheric conditions with variable temperature and irradiation levels, system performance and efficiency is evaluated and it is observed that the designed controllers are capable to operate PV panel at its maximum power point under different atmospheric conditions and provide constant DC voltage to the load while charging the battery with excess power. Introduction Conventional energy resources, expected to deplete in a near future unavoidably, take the first place in global energy production which cannot satisfy the need due to increasing population and industrialization. The gap between the energy production and consumption increases with each passing day [1]. Additional environmental problems arising from the production and consumption of conventional energy sources increased the interest in renewable energy sources worldwide; especially interest in PV systems has increased considerably in recent years. With the increase in research and development activities in photovoltaics, demand for PV systems has increased each year with an average of 20-25% in the last 20 years [2, 3]. The voltage and current values obtained from PV panels varies according to the load profile and atmospheric conditions [4, 5]. Consequently, the maximum power value that can be obtained from the PV panel varies depending on the atmospheric conditions. Through the use MPPT, higher energy conversion efficiency can be ensured with less PV panels and lower cost PV systems [6]. For such maximum power point tracking to improve efficiency and output voltage regulation; DC/DC converters, inverters and electric batteries can be used [7]. In this study, design and modelling of an MPPT controller to obtain maximum power from the PV panel, buck and boost DC/DC converters for output voltage regulation and battery charging to provide power for other DC loads connected to the system and PID controllers generating duty cycle for PWM switching DC/DC converters are performed. Overall system is simulated with MATLAB/Simulink-SimPowerSystems toolbox, results regarding the output voltage regulation and battery charging and future studies are discussed. Components of the PV System Main components that constitute the PV system and which are detailed in this section are shown in Fig.1. Figure 1. Main components of the PV System PV Panel. In order to design and model the PV panel, design parameters regarding the PV system input and output, are determined as given in Table 1. Table 1. Design Parameters Regarding the PV System Design Parameter Numerical Value Unit Resistive Load 5 ± 20% Ω Required Output Voltage 12 ± 5% V Irradiation Level Temperature Level 600-1000 20-30 W/m 2