Research On The Influence Of Phase Sequence Exchange Technology On Relay Protection And The Predictive Control Of Phase Sequence Exchange Technology

With the continuous expansion of power grid,power system is.always faced with the challenge of stability.In order to solve the problems of system oscillation and angle instability,our research group proposed a new stability control measure-phase sequence technology.The "phase sequence" will change the inherent connection mode of the three-phase power system,resulting in the change of the electrical quantity measured at the protection installation,which will affect the original relay protection of the power system.In addition,phase sequence predictive control is also an important research part of phase sequence technology,and the prediction of the system’s disturbed trajectory can provide a basis for the judgment of system stability and the formulation of phase sequence strategy.The topic selection of the paper has important theoretical significance and the value of prospective research.Centering on the two aspects of phase sequence technology,the main research results are as follows:1.The changing process of electrical quantity and its influence on protection when the phase sequence device is installed at different positions are analyzed in detail.By solving the time domain equation and characteristic equation,the changing process of power frequency component and non-power frequency component of electrical quantities is analyzed.The results show that in the phase sequence,the voltage and current at the protection will have a sudden change,and the voltage and current also contain a variety of transient components.The changes of these electrical quantities will affect the protection.2.For the phase sequence device,the design scheme is put forward,which is installed between the transformer and the bus,and the protection is arranged independently.So that the influence on the differential protection is very small.For section I of the zero-sequence current protection,the countermeasure of increasing small delay time is put forward to prevent the misoperation.During the phase sequence,section I and section II of the distance protection have entered the oscillation locking mode,and no special measures are needed.3.The key point of phase sequence predictive control is the prediction of the disturbed trajectory of the system.Firstly,trajectory prediction models are established by using typical trigonometric method and autoregressive method respectively.Then,the prediction effects of the two prediction models under different working conditions and different step sizes are compared and analyzed.It is concluded that the autoregressive prediction model has the characteristics of high precision,fast calculation speed and strong adaptability,which can provide strong support for the phase sequence prediction control.MATLAB/SIMULINK and PSASP were used to simulate the above influence,countermeasures and prediction model,and the results show that the countermeasures adopted can effectively suppress the influence of phase sequence technology on relay protection,and the autoregressive prediction model has good effect of disturbed trajectory prediction.