Out-of-step Islanding Measure Configuration Based On Generators Disturbance Simulation Trajectory Coherency Identification In Great Power Grid

With the rapid development of economy in our country, the future demand for electricity will continue to increase. But with the deterioration of environment problems, such as the fossil energy depletion and climate warming, the power structure will continue to be adjusted, in which the proportion of fossil energy will be reduced, the proportion of non-fossil energy power generation will tend to increase, the proportion of renewable energy sources such as wind, solar, biomass and the proportion of nuclear power would be a big rise in the future, the hydroelectric power in southwest, thermal power and wind power generation in northwest and northern, the nuclear power in eastern, and the distributed new energy power generation needs to be developed more quickly. In the future development, the main characteristics of our power grid will be large-scale power connection to grid and through EHV long AC-DC large-scale electricity transportation in a long period of time, which is decided by the unbalanced distribution characteristics of our energy and load. The large-scale interconnected grid is conducive to the allocation of resources and improvement of system stability, but also brings challenges to system safe and stable operation.This thesis makes a conclusion on the research status of out-of-step islanding and coherency identification, and analyzes the mechanism that the generator-group occurs out-of-step oscillation based on slow coherency theory. It studies the simulation variable selection based on the definition of unit coherency and simulation window selection based on PSD-BPA. The disturbance generators is divided according to the above selected simulation variable and simulation window, then the consistence of the generators disturbance simulation trajectory coherency identification and its counterpart originated from simulation result after islanding operation based on oscillation center location method is analyzed. Finally, the islanding measure and islanding sequence is improved based on coherence identification, the out-of-step islanding measures coordination and the improvement of islanding measure based on coherency identification and its coordination is focused based on the northeast power grid in 2013, and the process of out-of-step splitting based on generator disturbance simulation trajectory is proposed on the basis of the above steps. The main contributions of this paper are as follows:1) The occurrence of out-of-step oscillation in asynchronous generator-groups is a reflection of multiple time scale characteristics of power system in great power grid. When the system occurs great disturbance, the coherency generator-group remains stable easily for its internal fast dynamic attenuating rapidly and the asynchronous generator-groups occurs out-of-step oscillation easily for their slow dynamic being inspired.2) The definition of the generator coherency is analyzed, then the frequency deviation is selected as the observation variables which is equivalent to generator speed deviation, also the [0,3]s and 1Hz is selected as the observation window.3) The disturbance generators is divided according to the above selected simulation variable and simulation window, and the consistence of the generators disturbance simulation trajectory coherency identification and its counterpart originated from simulation result after islanding operation based on oscillation center location method is analyzed. Then the conclusion is that the generators disturbance simulation trajectory coherency identification can be used to guide grid islanding in the condition that the number of out-of-step generators is large.4) The improvement measures of setting islanding section in asynchronous generator-groups and the islanding sequence principle that the main oscillation section should be split first and then the secondary oscillation section is split in multi-group pscillation is proposed based on study of coherency identification. Finally, aiming at the maloperation of low voltage islanding device in islanding measures coordination of the conventional islanding scheme, the islanding measures are improved based on coherency identification, and the improved islanding measures coordination is analyzed based on the northeast power grid in 2013. Then the conclusion is that the naloperation and refusing action can be effectively avoided in the scene of more than one sets of measure device being set in the grid when the islanding measure is set pased on coherency identification.