Modeling And Simulation Of Hydrogenerator System With Doubly Fed Generators And Its Intelligent Control Strategies

Hydrogenerator system with doubly fed generators (DFG) is a new type waterpower system. The stator of DFG is connected to the grid and the three symmetrical excitation windings in the rotor are fed by converter. The magnitude, frequency, phase and phase sequence of excitation voltage can be controlled, so the magnitude and position of excitation MMF as well as the speed of rotor can be controlled. Therefore, DFG have superior performances such as good stability, variable speed constant frequency (VSCF) generation, active power and reactive power regulation independently, and lag reactive power absorbing deeply. By the united control of DFG excitation system and the hydroturbine governing system, this hydrogenerator system can be operated round the optimal unit speed of hydroturbine, improved the hydraulic efficiency and optimized load regulation when the water level or water flux is changed. Hydrogenerator system with DFG is a synthetical system including water, hydroturbine and generator portion. Considering the water hammer effect,this hydrogenerator system has some characteristics such as the system's nonlinear and great inertia, the system's parameters variation, the system's multi-variable and coupling characteristic. In order to study the operation performances of this hydrogenerator system, it is very important to study the model of hydrogenerator system with DFG and its intelligent control strategies. The main contents in this thesis are as follow:(1) Based on analysis of the internal electromagnetic relationship of DFG, the steady state operation performances of DFG are studied as well as the calculation methods of electromagnetic power for DFG are proposed incorporating harmonic components in rotor current.(2) According the load optimal regulation principle of hydroturbine, the load optimal regulation performances are analyzed at the same operation state for DFG and the conventional synchronous generator in terms of XIAO LANGDI hydroturbine regulation characteristics. The mathematical models of hydroturbine optimal regulation characteristics are established by using an improved Back Propagation (BP) neural network algorithm.(3) Based on the excitation control model of DFG and the control model of hydroturbine water valve, the mathematical models of the hydrogenerator system with DFG are established by using the small signal error method. Furthermore, a sufficient condition for the approximate stability in the large field of this generator system is derived by using the concept and method of the Lyapunov function.(4) According to the features of uncertain and nonlinear as well as parameters time-variation for the hydrogenerator system with DFG, a self-adaptive control strategy based on the cerebellar model articulation controller (CMAC) neural network is presented in this thesis. The digital simulation of the load optimal regulation performances, disturbance rejection performance, robustness and transient operation characteristics for hydrogenerator system with DFG are studied by using the proposed control scheme. (5) Regarding this hydrogenerator system as a black box, a decoupling control strategy based on fuzzy neural network algorithm is also proposed in this thesis, as well as the convergence of this controller algorithm is studied. Using the proposed control strategy the digital simulation of the load optimal regulation performances, disturbance rejection performance, robustness and transient operation characteristics for hydrogenerator system with DFG are studied.