EXCITATION SYSTEMS FOR MOTOR-GENERATORS IN THE BAJINA BAŠTA PUMPED-STORAGE HYDROPOWER PLANT

The run-of-river hydropower plant HPP "Bajina Bašta" and the pumped-storage
hydropower plant PSH "Bajina Bašta" in Perućac are the largest hydropower facilities built on
the Drina River. PSH "Bajina Bašta" is of great importance to Serbia's power system due to its
ability to operate in both generating and pumping modes, thereby increasing the system's
flexibility in terms of managing production and consumption. Periods of lower electricity
consumption 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 the
release 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 pumping
modes, this plant can quickly respond to system disturbances and replace any other unit in the
electrical power system of Serbia. Therefore, the revitalization of PSH "Bajina Bašta," which
is expected to extend the lifespan of the units by several decades, is of great importance to the
power system. In 2024, the first unit was revitalized, while the revitalization of the second
unit is scheduled for 2025. Nikola Tesla Institute of Electrical Engineering participated in the
revitalization by replacing the excitation systems. The power section of the excitation system
includes high-performance components: excitation transformers, circuit breakers, thyristor
bridges, demagnetization equipment, etc. The control section of the excitation system is based
on certified INTROL excitation regulators developed and manufactured at the Nikola Tesla
Institute. Within the regulators, sequential automatons are implemented for all operating
modes of the units: generating mode, pumping mode, synchronous start, electric braking, and
testing. INTROL regulators enable various control modes: automatic stator voltage regulation,
automatic reactive power regulation, and automatic power factor regulation, along with
limiter functions and a power system stabilizer. The thyristor bridges and excitation regulators
are implemented redundantly in a 1+1 configuration. After installation and connection, the
excitation system was adjusted and tested, demonstrating good system performance, enabling
reliable and stable unit operation in all operating modes, with automatic operation limitation
within the boundaries defined by the operating diagram.