Investigation of the effects of fuzzy logic and PI controllers on development of FRT capacity of a statcom-supported PV generator

With the rapid progress of technological developments in parallel with the increase in human population in the world and in Turkey, the need for large-scale energy has emerged. While the energy obtained from fossil fuels met this need until recently, it was insufficient to meet today's energy demand. Both the rapid depletion of fossil fuels and the unlimited source of renewable energy have led to intensifying studies and research in this area. In the first periods when renewable energy came into our lives, renewable energy power plants were installed independent of the grid and distributed in areas where access to the grid was difficult. However, with the rapid increase in energy need and the establishment of these power plants in places where continuity in energy flow is essential such as farms, schools, hospitals, they have now been turned into power systems that work in connection with the grid. The fact that renewable energy sources(RES) do not have a fixed production value has made the amount of energy to be drawn from these power plants uncertain. Unpredictability of wind performance, clouding time, dusting of solar panels, unknown amount of wave formation etc. circumstances are the main causes of this uncertainty. Unbalanced situations may occur between the grid and the RES connected to the grid and the power quality can deteriorate. This imbalance has made power quality issues important and studies on this subject have increased in recent years. Various solution methods have been developed to prevent such negativities. In this thesis, it is aimed to improve fault ride through (FRT) capacity through flexible alternating current transmission system (FACTS) devices in a power system with a grid-connected photovoltaic (PV) plant. The methods of FACTS devices used to increase the FRT capacity have been analyzed in itself by considering important issues such as cost, space coverage and heating. The determined FACTS device is activated or deactivated after it is passed through a controller that accepts current or voltage values from sensors at the common junction (PCC) and works according to traditional or smart methods. The most widely used FACTS method today is the "static synchronous compensator (STATCOM)" method, which provides reactive energy to the power system or draws reactive energy from the system. The ability to control the output current (inductive or capacitive) of STATCOM, which is an external device-based FACTS method, independently of the AC system voltage has made it superior to another external device-based FACTS device, the static var synchronous compensator (SVC). In the grid-connected photovoltaic power system (PVPS) model created in the Matlab Simulink application, some fault types were created and the reliability and stability of the system were tested. These fault types are: a phase fault, phase-phase fault, phase-phase-ground and three-phase-ground faults. In order to ensure that the system is stabilized more quickly in case of failure, STATCOM is activated or deactivated with the developed control methods. These control methods are proportional-integral (PI) controller and fuzzy logic controller (FLC) structures based on mathematical method. Two different cases were studied by using STATCOM with PI controller based on the mathematical model and STATCOM with FLC based on the smart method. By evaluating the results obtained from these working situations, the performances of the developed controllers on the FRT capacity were compared. In case of three phase-to-earth fault transition, the maximum overshoot with the PI controller has been reduced by 80% with the realized FLC. The values in this operating condition were compared and it was seen that the response time of the FLC was 75% more successful than the response time of the PI controller. With the FLC-based STATCOM control method developed in the thesis study, a suitable structure has been created to improve the power quality and increase the stability of the system in grid-connected PVGS.