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.