Desenvolvimento do protótipo de um relé digital para geração distribuída com integração para redes inteligentes

Abstract

With new standards, government incentives and concerns about environmental questions, is expected the growth of the number of generating units connected to the grid from consumers. Some technical issues related to the high penetration of distributed generation on distribution feeders concerns the power utilities, which look for solutions to prevent possible unwanted effects on the electrical system. This research presents the development of a digital relay applied to protect the interconnection of distributed generation in the grid, focusing on micro and mini electricity generation plants from synchronous and asynchronous generators, and inverters. The digital relay contains the main protection functions required by PRODIST and utilities standards, including anti-islanding algorithms. Its operation is given by the measurement of electrical parameters at the point between the distributed generation and grid, followed by digital signal filtering and protection algorithms processing. Like a conventional digital relay, the protection functions can be individually configured, it’s possible to build logical and blocking expressions with them. The prototype can be monitored and controlled by a personal computer connected in the same local network. The computer must run an interface program. The prototype allow remote control by the utilities, this communication is done by a mesh network installed along the electric distribution system, using the ZigBee protocol. It’s presented a review about the effects and problems caused in the electrical power system by the distributed generation, giving the context of the future Brazilian distribution network in relation to the actual situation of more experienced countries on distributed generation. Following, it’s presented the main technics of digital signal processing applied to digital relays and operation of the protection functions. So then, the details of the hardware development, digital filtering strategies and the implementation of the protection algorithms are presented. Some technics applied to the filtering algorithms and protection function, as the three-phase frequency measurement using Clarke’s transformation, are discussed and evaluated. The test results of the prototype operation are presented, the tests were done in laboratory. The digital relay contain a set of protection functions that covers the main standards of distributed generation access in Brazil, it’s possible to use as a backup protection for systems with protections embedded, as grid tie inverters, and the possibility of remote control of distributed generation through the mesh network with ZigBee protocol.