Research On Small Disturbance Stability Of Power System Containing Wind Power Based On Unscented Transformation Method

The actual development of wind energy in some countries in the world has made it the fastest growing power generation technology between sustainable and clean technologies.Almost 50% of installed wind turbines are induction generators.With the increase of the number of induction generators replacing synchronous generators,the power system is experiencing different disturbances.For weak grid-connected wind power systems,small disturbance stability has become a hot topic in the field of new energy generation at home and abroad,which requires the study of small disturbance stability of wind power systems.At the same time,due to the annual increase in equipment requirements of the State Grid and the requirements of power supply companies for economic benefits,low-frequency oscillations caused by weak damping modes have become an important reason for limiting the operation of the State Grid.Therefore,this paper proposes a small disturbance stability analysis method for power systems with wind power based on the unscented transformation for the uncertainty of random factors related to load levels in power systems,which can be applied to explore the effect of doubly fed wind turbine access on small disturbance stability of power systems.In this paper,the power system analysis toolbox(PSAT)on MATLAB is used for simulation analysis to conduct simulation analysis to explore the issues of wind power and small disturbance stability of power systems.Firstly,the analysis method of small disturbance stability and the small disturbance stability analysis method in PSAT are comprehensively described;Then the mathematical model of the electrical system and mechanical system of the fan is established.The electrical system includes the model of the double-fed induction fan,and the mechanical system includes the model of the wind turbine,mechanical transmission,frequency converter and pitch angle control.Secondly,a small disturbance stability analysis method based on the unscented transformation method is proposed.This method converts the probability analysis problem into the deterministic analysis problem through the symmetric sampling strategy,and then calculates the small disturbance stability evaluation index according to the weight distribution of each sampling point in the traceless transformation method,which is verified by examples in the 3-machine 9-bus system and the 4-machine 11-bus system.The simulation results show that the relative error between the results of the unscented transformation method and the Monte Carlo method is very small,but the time of the unscented transformation method is much shorter than that of the Monte Carlo method,which enables the rapid evaluation of the small disturbance stability analysis and meets the requirements of Engineering applications.Finally,small disturbance stability analysis is carried out for the 3-machine 9-bus system with wind power,the 4-machine 11-bus system with wind power,and the 10-machine 39-bus system without wind power and with wind power in New England,further demonstrating the effectiveness and practical value of the proposed unscented transformation method.The report results of eigenvalue analysis in PSAT for a New England 10-machine 39-bus system without double feed fan show that the correlation of each generator unit to different oscillation mode correlation factors can be directly obtained,thereby obtaining the most relevant units for each oscillation mode.