Research On Control Of Electromechanical Disturbance Propagation In Power System

Under the development of interconnected power grid, it becomes more and more huge, somewhere in the arbitrary perturbations are likely to affect the safe and stable operation of the grid, so study of power system electromechanical disturbance propagation and suppression method is very important。With the development of wide area measurement system, more and more data show that the propagation of electromechanical disturbance in the system, such as the active power and the speed of the generator, presents a spatial and temporal distribution characteristics. Electromechanical wave theory main researchs these physical quantities in the grid and theoretically explains electromechanical dynamics of spatial and temporal distribution characteristics.It is a new method for exploring power system electromechanical dynamic process.The existing research results of electromechanical disturbance propagation are summarized and overviewed in this paper.lt describes the process from vibration to wave and which shows thougt of the discrete model to the continuum modeling in the elastic space, and according to this kind of thought the power system electromechanical wave equation is derived. The contact of disturbance propagation in power system and elastic space are described, compared, and the relationship between them is explained. The vibration mode decomposition method for solving the multi degree of freedom vibration system is introduced and it can also be applied to the analysis of electromechanical disturbance propagation.According to the discrete power systems complex frequency domain model, rules of equivalence between the electromechanical disturbance in the uniform infinite system and in the zero reflection system propagation, a new simple method for taking the electromechanical disturbance propagation characteristic impedance is derived. Based on the theory of continued fractions, discrete power system electromechanical disturbance propagation zero reflection control method is given, The input signal by the increment of the rotor speed and the transmission power of the transmission line is simulated and verified respectively, the simulation shows the inhibitory effect of this method to electromechanical oscillation amplitude and it enhances the ability of power system to resist electromechanical disturbance. The analytical expressions of the generator rotor’s increments and power increments at all buses are derived under the impacts of unit-step excitation within an infinite-length uniform chain power system. The simulation verified the correctness of the analytical solution. Based on the power system transmission line and generator equivalent impedance, using the research methods of linear circuit, power system electromechanical disturbance propagation in the transfer function block diagram are given, and it can be used for the simulation of the propagation characteristics of disturbance.Finally, this paper analyzes the discrete model of power system disturbance propagated to the boundary effect, obtained the relationship of the disturbance power fluctuation when electromechanical disturbance occurred zero reflection and zero transmission in the same position, and the relationship were analyzed in the complex frequency domain and time domain. Using power system electromechanical disturbance propagation delay characteristics, puts forward a pre-start controller of electromechanical disturbance zero transmission control method, this method can better to overcome the controller response delay which causes large transmission power. This controller zero transmission effect is validated by simulation. The results show that the method can effectively reduce power transmission and limit the electromechanical disturbance in the designated area.