Research On Synchronous Generator Mathematic Model For Power System Stability Analysis

The dynamic operation capacity of synchronous generator after disturbance of power system is very important to guarantee the safety and stable operation of power system. This dissertation has established Time-step Finite Element Model (T-S FEM) to study the operation capacity of synchronous generator under system disturbance, and studied the influence of rotor damping structure and damping material characteristic of turbine generator on power system stability. The results calculated by T-S FEM are compared with the practical models of synchronous generator used in power system simulation. Take the results of T-S FEM as target curves, the parameters of practical model in large disturbance process is identified. The main works are as below.1. The Time Step Finite Element Model used to analysis the influence of three components damping structure of turbine generator and damping material characteristic on dynamic characteristic of power system is built. Considering the complex rotor damping structure of turbine generator, we make crucial improvements in space-time discrete strategy to consider the eddy current skin effect of rotor damping structure affected by multi-factor nolinear. This model is tested by the experiment of model machine.2. Take a300MW turbine generator as an example; we reveal the relationship between rotor damping bar, rotor conductive slot wedge, rotor iron core of turbine generator and the First Swing Stability through the computational analysis of T-S FEM. And we also find that the influence of rotor damping structure on First Swing Stability is depended on its equivalent resistance. Further, we study the First Swing Stability affected by rotor slot wedge of different materials and reveal the change law of first swing stability limt along with the conductivity of rotor slot wedge.3. The physical essence of two practical models is reavled in theory. The assumed A model takes account of the mutual leakage flux linkage between field winding and damping winding, neglects the self-leakage flux linkage of damping winding; it is opposite to the assumed B model; while assumed B-1model is obtained by neglecting the something about damping based on assumed B model. The simulation results of small disturbance and large disturbance by three practical models is compared with the T-S FEM, and the results difference of different models is obtained.4. The influence of stator winding transient (p(p) on electromechanical transient is studied by analytical expression and numerical simulation. It is found that the fundamental frequency oscillatory component of electrical torque and unidirectional component of electrical torque due to stator aperiodic current during three phase short circuit of generator is neglected, when the stator winding transient is neglected. The unidirectional component of torque has a braking effect. Its effect is to reduce the rotor acceleration following the disturbance and improve the first swing stability.5. Take the large disturbance results of T-S FEM as target curves, the parameters of synchronous generator are identified through the least square method. We obtain the change law of these parameters along with power angle of generator and find that the precision of identification parameter is higher than factory parameters. Meanwhile, the parameters are identified under different rotor slot wedge materials and find that the influence of rotor slot wedge conductivity on the paremeters of generator. The study results provide theoretical support for the further improvement of practical model.