UNiversal controller for the interconnection of distributed generators with utility lines at customer level voltages

This paper presents the design, construction and performance testing of a controller capable of protecting the utility from any negative side effect of the interconnection of distributed generation (DG) at customer level voltages. The controller is universal in the sense that it allows for the interconnection of all kinds of distributed generators: synchronous, induction and those that need a power electronic converter (solar, fuel cell, micro-turbine, etc.). The controller assures that the IEEE standards 1457 for the interconnection of DG and utility standards are complied. Additionally, the controller cuts the fault current in less than a cycle to prevent the increase to the shortcircuit duty of the already installed protection equipment. This is especially important in the case of a synchronous interconnection in locations where the short-circuit power of the substation breakers is close to its limits. A 25 kVA utility grade prototype controller has been built and tested in the lab.