The independent production of electrical energy represents a vital economic activity and is an important objective of virtually every national policy, as it enables operational self-sufficiency and independent supply. By exploiting renewable water resources, hydro-power plants significantly contribute to the production of electrical energy. Secure and reliable electrical production in conjunction with integral ancillary services (control of frequency, power and voltage; black start; gradual load rejection, etc.) are the most important objectives of hydro-power plant operations. Long-term operative experience and multiple ongoing experiments on real systems are essential for acquiring knowledge and expertise on the optimal operation and maintenance of hydro-power subsystems and their functions. Yet, deregulation of the electricity market and strict dispatching schedules permit executing tests on real systems only with prior announcement or during systems maintenance work. It is therefore imperative to develop reliable simulations that enable testing conditions which cannot be performed on real systems and which lead to advancements in systems improvements.
This paper presents a proposal for the development of a complex dynamic model of the hydro-power plant located in Mavčiče, Slovenia. The model includes essential dynamic properties of the aggregate’s subsystems and its proximate 110-kV electrical network. The simulation provides an analysis of operational scenarios that cannot be tested on real power systems.
The simulation model developed in this research enables execution of the simulation program in phasor and continuous modes. The impact of a stepwise increase and reduction of the generator’s active power on the 110-kV transmission lines was first simulated using the phasor method. The results of this simulation are validated using in situ measurements on the Mavčiče hydro-power plant and its nearby 110-kV transmission lines with different performance indexes. The simulated disturbance of the frequency is then considered in terms of its impact on the turbine controller, excitation system and consequently, on the generator’s active power and power flow on the 110-kV electrical network. The simulation model in the phasor mode of the Mavčiče hydro-power plant provides an analysis of the dynamic response of the selected aggregate at changed operating parameters as well as the impact of disturbances. It further allows testing new control algorithms and contributes to the improved design of primary and secondary electrical equipment.
In contrast with the phasor mode, the continuous mode is more appropriate for conducting short-term simulations with high sampling frequency. In the scope of this part of the research, a three-phase short-circuit current located at two different locations was simulated in continuous mode. The results of this simulation indicate that the size of the three-phase short circuit is dependent upon the location of the occurrence. When the three-phase short circuit is located between the selected generator and transformer, the total maximum short-circuit current is higher as compared to when the three-phase short circuit is located on the 110-kV busbars of the Mavčiče switchyard. The results of this simulation were compared with the calculation of the maximum three-phase short-circuit current in compliance with IEC standard. Simulation in continuous mode enables conducting the most demanding tests on installed electrical and mechanical equipment, preventing any damage that could result if tests were carried out on real systems in practice.
Taking into account the analyses of the selected simulation scenarios produced in the scope of this research enables electrical energy producers to acquire integral information on how power subsystems would react when introduced to new control algorithms and indicates reliable results of tests that are not feasible to carry out on real systems in practice. This ensures effective design of new equipment that leads to enhancing the reliability of hydro-power plant operations, a more efficient exploitation of water resources and the exemplary execution of ancillary services that contribute to national energy self-sufficiency and the independent supply of electrical power.