Performance Analysis of Distributed Synchronous Generators with Controllers Equipped with Switchable Operating Modes

Synchronous generators of industrial plants with cogeneration typically operate in parallel with the main utility grid. These machines are usually equipped with excitation controllers operating in constant power factor mode, and speed controllers working in droop mode. While such control techniques are well suited for steady state operation condition, on the other hand, they prevent the generators to act in a favorable way in response to any disturbance that may lead the electrical power system (utility and industry) to instability. This work aims to evaluate the performance of distributed generators with proper switchable controller operation modes using the ATP (Alternative Transients Program) to perform the computer simulations. In simulated cases, the speed controller automatically switches to the isochronous mode if the industrial system loses connection to the main grid. Besides, the excitation controller also automatically changes to the voltage regulator mode for not only this type of occurrence, but also when voltage sags due to power system overloads take place. The results show that the desirable performance of synchronous generators is achieved, as to voltage and rotor stability, when an expanded strategy for their controller operating modes is adopted.