| With the complexity of the network structure and operation mode of power system,the dynamic response of the power system after failure in the cross regional interconnection grid often shows more complex instability mode.In order to apply the phase sequence exchange technology to the actual power system better,this paper studies the critical group identification and the control method of phase sequence exchange technology in multi-machine system based on the research results of the research group on the phase sequence exchange technology under the single machine infinite system model.The main results are as follows:(1)For the simple three-group instability mode in multi-machine system,the multi-machine system is divided into critical group,intermediate group and residual group according to the order of generator power angle.Then,for the generators in the intermediate group,the group criterion formula of transient energy is proposed.The generators in the intermediate group will be divided into new critical group or residual group,and equivalent to two-group modes.The system instability control is realized by using phase sequence exchange technology for the final critical group.(2)For the complex instability mode of multi-machine system,the same method is divided into critical group,intermediate group and residual group.Then,according to the subordinate degree of the power angle trajectory of generator in the intermediate group,the generators in the intermediate group are divided into the new critical group and residual group,and an initial critical group with fuzzy properties is obtained.Then,the generators with fuzzy state in the initial critical group are judged in turn.The formula of the group classification criterion is put forward.The generators with fuzzy state in the initial critical group are further divided into the critical group and the residual group,until all the generators in the initial critical group have the definite group state,and the final critical group is obtained.(3)Based on the identified critical group,combined with the bump of the power system phase trajectory,the transient stability of the system before and after the phase sequence exchange operation is judged,and the control method of "transient stability prediction,phase sequence exchange operation and transient stability judgment" in multi-machine system is formed,and the purpose of stable control of phase sequence exchange technology in multi-machine system is realized.The simulation of the New England 10-machine,39-bus system is carried out in MATLAB/Simulink.The simulation results show that the research results can not only identify the critical group of the system to perform the phase sequence exchange operation quickly and correctly,but also can judge the transient stability of the system correctly.The system stability is greatly improved by combining the method and the phase sequence exchange technology. |
