Study On Stability And Economical Efficiency Of Ac Excited Hydrogenerator Unit Operation

ACEHU (AC Excited Hydrogenerator Unit) is a new type of hydro-electric power equipment, with the inverter power providing generator with symmetrical AC excitation, and the amplitude, frequency, and phase of the excitation voltage being controlled in accordance with the requirements. The size of the magnetic field excitation, the location of the rotor and the motor speed can be controlled, so that the ACEHU has VSCF (Variable Speed Constant Frequency) power generation and deep condensive operational capabilities, independent active and reactive power regulation capacity and good stability. Compared with the traditional SGU (synchronous generator unit), the ACEHU can flexibly adjust reactive and active power and improve the system's stability. In addition, through the coordinated control of generator excitation and hydroturbine speed governing, the hydroturbine can operate around the optimal speed during the time of head and flow rate changes, achieve its optimal operation of variable speed, and then improve water use efficiency, save water and enhance effectiveness of unit operation. Therefore, it is of great practical significance to study the stability and economical efficiency of the ACEHU. So this thesis is devoted to the stability and economical efficiency study of ACEHU operation, and its main contents and achievements are as follows:(1) Model study is conducted as the basis for analyzing and calculating ACEHU operation stability and economical efficiency. Based on the ACEG(AC Excited Generator) mathematical model under the rotor magnetic field dq0 coordinates, corresponding fifth-order and third-order practical model under the rotor magnetic field dq0 coordinates is further detailed derived and explained, and the excitation system model under the stator voltage-oriented vector control strategy is established. Integrated related results, the linear hydroturbine model and the model of hydroturbine speed governing system under PID control strategy are established; the elastic water-hammer equivalent circuit model of the complexity conduit system with pipeline, tailrace and tailrace tunnel is established.(2) The simulation research on ACEHU improves power system stationarity and stability is done. Based on the ACEG practical model, control model of excitation system, hydroturbine model, conduit system model and speed governing system model, the simulation model of the ACEHU is set up under the Matlab/Simulink. For the SMIB (single machine infinite bus) system and the multi-machine system containing the ACEHU, load adjustment of small disturbance and short-circuit fault of transient process simulation are separately conducted. The results show that compared to the traditional SGU, the ACEHU can achieve independent active and reactive power regulation, fast response, and can significantly improve power system stability.(3) The characteristic of variable speed operation of the ACEHU makes it possible to improve water saving and operation effectiveness of the hydrogenerator unit. In this dissertation, the further study of water saving and operation effectiveness is done. Based on the hydroturbine integrated characteristic curve fitting, the method of using Genetic Algorithm to find speed optimization of ACEHU is proposed. A calculation analysis is made on the efficiency, water consumption and power generation effectiveness of the ACEHU variable speed operation when it is under different head and power conditions. The results show that the method to find speed optimization of ACEHU which is proposed in this dissertation has high calculation accuracy; compared to the traditional hydrogenerator unit, the ACEHU has significant benefit of water-saving and more power generation.