Um sistema de proteção de sobrecorrente direcional adaptativa baseada em lógica fuzzy para sistemas de distribuição de energia elétrica com geração distribuída fotovoltaica.

Abstract

In recent years, there has been a growing increase in the generation of electricity close to consumers, known as distributed generation. In Brazil, photovoltaic technology accounts for more than 99% of consumer units with installed distributed generation. Despite the recognized advantages, it is known that the insertion of new generating sources into an electrical power distribution system, which was designed to operate unidirectionally, can lead to changes in power flow and, consequently, cause several problems, particularly to the protection system of traditional electrical power distribution systems. Therefore, this Thesis proposes an adaptive directional overcurrent protection for electrical power distribution systems with photovoltaic distributed generation. The solution is based on the concept of fuzzy logic, being able to adjust the pickup current value used in the digital inverse time operating curves applied to both directional overcurrent relays and digital reclosers online. Using a centralized architecture (modeled in the Simulink/MATLAB® environment), which is characterized by containing a computer located at the substation that controls the entire protection system, the proposed system monitors and processes the analog and digital channels of the relays and reclosers, resulting in the variation of circuit breaker states and the active power of the distribution system, which are used as indicators of changes in the operating scenario. If a scenario change is identified, the proposed system recalculates the pickup current, using the load current and short-circuit current as input variables for the fuzzy logic. To validate the proposed solution, the IEEE 34-bus and 69-bus test systems are simulated in Simulink (MATLAB®) software, allowing the nominal power of the distributed generation, the loading of the distribution system, and the type of short circuit to be varied. Three scenarios were evaluated: i) location of the installation of photovoltaic generators; ii) topology change; and iii) variation in feeder loading. The results obtained confirm the benefits of the proposed solution. Making changes to overcurrent protection with the insertion of distributed generation can be fundamental to ensure the sensitivity of the devices and correct operation to ensure the coordination of directional overcurrent protection and ensure the continuity of the distribution system service.