Comparison of controllers used in a converter with two-stage topology in standalone single-phase PV inverter structures

In recent years, there have been many studies on how to reduce environmental pollution in the world by using clean energy sources such as solar, wind, hydroelectric, biomass and biogas. For this reason, the consumption of fossil fuels is reduced and the focus is on clean and renewable energy sources such as hydroelectric, solar, wind, geothermal and wave energy. The sun, one of the most important renewable energy sources and the only inexhaustible energy source, is a clean energy source that does not contain any waste. It is possible to utilize solar energy almost everywhere where it is needed. Solar energy is used in many areas due to its numerous advantages. The most common areas of use are PV systems. PV systems are divided into two groups as grid-connected and off-grid mode systems. In this study, a single-phase PV system with off-grid mode was examined. In this system, there are two power electronic converters between the PV panel array and the load. Both converters are controlled by a controller. The first one was used to ensure that the power at the output of the boost converter follows the maximum power point for different irradiance and temperature values and the second one is used to ensure that the alternating voltage at the output of the inverter has minimum harmonic distortion and stable amplitude for different values of the load. Three different control structures were used for the control of the boost converter. These are perturbation and observation algorithm from traditional methods, fuzzy logic method from intelligent methods and backstepping controller method from nonlinear methods. It was controlled using a backstepping controller in order to eliminate the error between the output voltage and the desired value during the load change at the inverter output. MATLAB/Simulink simulations of the standalone single-phase PV system are performed for performance comparison. Using the simulations, the controller structures used for different irradiance conditions and load variations are compared and the performance results are presented in detail. The simulation results show that the PV system with backstepping controller has high efficiency, stable amplitude and output voltage with low harmonic distortion.