Research On The Analysis Of Power System Oscillation And Splitting Strategy

Splitting control is the last one of the three defensive lines protecting power system from collapse.If the system comes across severe instability problems and emergency control strategies fail to bring it back to normal,splitting control will suggest cut the original interconnected network into several isolated islands according to certain rules.Such strategy can prevent the whole system from breaking down,and sustain service to most of the loads.With the development of interconnected network,splitting control will be used more and more widely.In this paper,the out-of-step oscillation center of two-machine system and three-machine system is studied,and a more perfect and reasonable strategy is proposed.The achievements are as follows:A method for out-of-step oscillation center of two-machine system considering the frequency difference of each point of the line is proposed.A more precise impedance model is constructed based on the linear distribution of frequency.The impedance of the bus is deduced,and the mathematics concept of the oscillation center is given by means of impedance complex plane.At the same time,the out-of-step center can be found out more intuitively and quickly.Out-of-step center position and oscillation center drift law are studied.Finally,out-of-step center location criterion and the analysis criteria of the comparison between the 180 degree and the power angle difference between the two ends of the line at the out-of-step time are given.The method of out-of-step oscillation center based on ring-shaped equivalent three-machine multi-frequency system is proposed.The nodal voltage expression can be deduced.By constructing the equivalent virtual machine at the node,the three-machine system is converted into three two-machine systems.Based on the characteristics of the phase difference between the three equivalent systems,the out-of-step oscillation center of the system is located.On this basis,the drift law of the oscillation center of the three machine systems under different tuning conditions is analyzed.The results show that the proposed method not only can accurately locate the oscillation center of the ring multi-frequency system,but also can explain the migration trend of the oscillation center reasonably and reasonably.A more perfect and reasonable splitting control strategy is proposed.A complete splitting control scheme includes not only where the splitting point is set in the power system,but also the auxiliary emergency power control measures and the voltage stabilization measures.Firstly,the coherency cluster identification is carried out based on the slow coherency theory.Secondly,the corresponding splitting control device is designed,and then the auxiliary power and voltage stabilization measures are provided,which aims at improving the traditional load shedding strategy and genertor shedding strategy.The strategy not only meets the needs of network stability operation when the large disturbance happens,but also meets the needs of network stability operation when the system collapse happens.