Research On The Identification Method Of Electrical And Mechanical Oscillation Type Based On Phase Trajectory

Electromechanical oscillation of power system is also called power system power oscillation and low frequency oscillation.The induction mechanism of electromechanical oscillation mainly includes two forms: negative damping power oscillation and forced power oscillation.The two modes of oscillation are similar,and it is difficult to distinguish them by oscillation alone.At the same time,random disturbance such as load drop is occurred in the system,which is normal for the system.Therefore,it is necessary to determine whether there is a sustained and stable electromechanical oscillation and what form of electromechanical oscillation when the transmission power of the system fluctuates.This paper identifies the types of electromechanical oscillations based on the phase trajectory analysis.The main tasks completed are as follows:The dynamic response characteristics of the system under three different excitation modes,such as shock disturbance,sinusoidal excitation and random perturbation are derived based on small interference analysis and system state equation.The calculation results are analyzed in depth,the analysis results show that three kinds of incentive forms can trigger system electromechanical oscillation and the response information contained in the information system oscillation mode.When the power grid transmission power fluctuation occurs,in order to determine whether it is steady electromechanical oscillation,electromechanical oscillation of power grid is proposed based on phase track type identification method,this method does not need to be calculated for oscillation parameters,can be in the form of image intuitive to distinguish between types of electromechanical oscillation.The characteristics of the phase trajectories of different electromechanical oscillations are analyzed by simulating various types of electromechanical oscillations.The concept of phase trajectory is proposed to quantitatively describe the change characteristics of phase trajectory so that the computer can automatically identify the system electromechanical oscillation type.The effectiveness and accuracy of the proposed method are verified by two simulation systems of IEEE 4 machine 2 area and IEEE 16 machine 68 node.In order to reduce the identification time of electromechanical oscillation type of the power grid,a fast identification method of electromechanical oscillation type was proposed based on the phase trajectory method.This method can accelerate the formation speed of phase trajectory without changing the topology of the phase trajectory,so as to effectively reduce the recognition time of system electromechanical oscillation type.The effectiveness and accuracy of the proposed method is verified by two simulation systems of IEEE 4 machine 2 area and IEEE 16 machine 68 node.