EXCITATION SYSTEMS FORMOTOR-GENERATORS IN THEBAJINA BAŠTA PUMPED-STORAGEHYDROPOWER PLANT

The run-of-river hydropower plant HPP "Bajina Bašta" and the pumped-storagehydropower plant PSH "Bajina Bašta" in Perućac are the largest hydropower facilities built onthe Drina River. PSH "Bajina Bašta" is of great importance to Serbia's power system due to itsability to operate in both generating and pumping modes, thereby increasing the system'sflexibility in terms of managing production and consumption. Periods of lower electricityconsumption are used to fill the upper reservoir by operating the plant in pumping mode.When the system requires additional energy, the units switch to the opposite mode, and therelease of water from the higher-altitude reservoir drives the turbines, generating electricity.Also, due to its ability to start quickly and rapidly switch between generating and pumpingmodes, this plant can quickly respond to system disturbances and replace any other unit in theelectrical power system of Serbia. Therefore, the revitalization of PSH "Bajina Bašta," whichis expected to extend the lifespan of the units by several decades, is of great importance to thepower system. In 2024, the first unit was revitalized, while the revitalization of the secondunit is scheduled for 2025. Nikola Tesla Institute of Electrical Engineering participated in therevitalization by replacing the excitation systems. The power section of the excitation systemincludes high-performance components: excitation transformers, circuit breakers, thyristorbridges, demagnetization equipment, etc. The control section of the excitation system is basedon certified INTROL excitation regulators developed and manufactured at the Nikola TeslaInstitute. Within the regulators, sequential automatons are implemented for all operatingmodes of the units: generating mode, pumping mode, synchronous start, electric braking, andtesting. INTROL regulators enable various control modes: automatic stator voltage regulation,automatic reactive power regulation, and automatic power factor regulation, along withlimiter functions and a power system stabilizer. The thyristor bridges and excitation regulatorsare implemented redundantly in a 1+1 configuration. After installation and connection, theexcitation system was adjusted and tested, demonstrating good system performance, enablingreliable and stable unit operation in all operating modes, with automatic operation limitationwithin the boundaries defined by the operating diagram.