A Fast Out-of-Step Center Locating Method Based On Wide Area Measurement Information

When the out-of-step oscillation happens in power system,if not handled in a timely and effective manner,it is likely to develop into large-scale security accident which can endanger the whole system stable operation and cause huge economic losses.Out-of-step splitting control is the third-defense-line of the power system.When power system run out-of-step,it can choose the right splitting surface to split the out-of-step system which can reduce the risks of out-of-step oscillation to the system.And the base of determining the splitting surface is the locating of out-of-step center.Also,a rapid accurate out-of-step center locating method is very important for the out-of-step splitting of power system.At present,most of the methods study the out-of-step oscillation are based on the in situ electric parameters.They have great limitations and are difficult to meet the requirement of out-of-step splitting in a real time change large scale power grid.With the continuous development of the wide-area measurement information system,out-of-step splitting can use the electric information of whole system and make calculation and splitting control based on the real-time operation state of system.An out-of-step center locating method based on wide-area measurement is proposed in this paper.First of all,based on the out-of-step oscillation characteristics,an out-of-step oscillation identification method of power system is given;Secondly,a phasor algorithm which can reduce the effect by the system frequency shift is studied,and it is suitable for using to the PMU to calculate the phasor amplitude and phase after the out-of-step oscillation;Thirdly,under the scene of the voltage amplitudes on both sides of the system are not equal and whole system impedance angles are not same,depending on three sets of voltage and current data from the wide-area measurement,by solving the intersection of measured impedance trajectory equation and the whole system impedance polyline equation,the locating method can confirm the component where the out-of-step center is.Theoretical analysis shows that: after oscillation,the scheme can locate the component where the out-of-step center is before the potential phase difference of the equivalent two terminal power system reaches 180°.The time when the out-of-step center appears can be determined using the relationship between real-time measured data and theoretical calculation values.The work done in this paper lays the foundation for the determining of out-of-step splitting surface and the choosing of splitting time.Finally,the effectiveness of the method is verified by simulation.