Overlapped Probability Based Applied Research For Assessment On Transient Voltage Stability Of Regional Power System Containing Wind Farms

With the continual growth of the economy, the demand for energy has been increasing accordingly, moreover, the traditional energy not only cannot be equal with the human’s increasing demand for energy but also make the environmental problems more serious than ever before. Therefore, the renewable energy is more urgent for human to meet with the demand for energy. In this way, being an important kind of green renewable energy, the wind energy, which is characteristic by the enormous energy deposit, unlimited advantage, has been developed and utilized massively from the very beginning of the21st century.After the wind power generation joining in the regional power grid, it will have an adverse impact on the transient voltage stability, for the wind generation has the disadvantages of intermittence and randomization, even, for the wind turbine generators don’t generate reactive power or absorb reactive power from the power grid. Meanwhile, the wind turbine generators has a tendency to take off the net,for the low voltage caused by the grid fault, which will bring greater threat to the transient voltage stability.Facing with the bad influence of the wind energy generation on the transient voltage stability, the reliable accesses on the impact are the requirement for the merging of the wind energy generation. At present, as for the study on the transient voltage stability towards the wind energy merging in the power grid, for the complexity of the transient voltage stabilization in wind energy region, most of the references are concerned about the key node of the transient voltage fault related to the wind, that’s to say, there are few references aiming at the general problems of the entire wind power region. The simplest feature set will be selected from the complex high-dimensional characteristic quantities of transient voltage stability, simplifying the analysis of the transient voltage stability in regional power area.The theory of overlapping probability algorithm is presented, based on the minimum probability of falling into overlapping space,selecting the simplest set to reduce the dimensional feature of electric system. Firstly, as for the selection of the original feature, the factor of wind power should be taken into account,establishing related wind power characteristic. Secondly, extracting the overlapping space of the original feature from a large amount of data. Thirdly, taking the minimum probability of falling into overlapping space as the criterion, the selection should be related to the original characteristic from the reliable access of transient voltage stability. Finally, through the selection of the simplest feature set, the transient voltage stability can be categorized based on the adoption of the pattern recognition of neural network.The overlapping space extracted from standard IEEE30-bus system, the overlapping space extracted from IEEE30-bus system with wind farm appended and the selected simplest feature set are compared, and the comparison results show that the description of the same power grid by the simplest feature set, which is composed by characteristic quantities with lower dimensionality selected from high-dimensional characteristic quantities by overlapping probability algorithm, is of higher accuracy, which is validated by neural network.