A new node contribution factors for the low frequency oscillations of power system based on the PMU's data and HHT

With the rapid development and interconnection of power systems, the low frequency oscillations(LFO) has become one of the serious factors threatening the power system stability. Thus, how to quickly locate the source of LFO and implement controller to suspend it, is an urgent task. The general approach to locate the sources of LFO is using the node contribution factor(NCF), which indicating the contribution of the node(generator) in the oscillation. This paper aims at proposed a new more effective method to calculate the NCF for LFO based on the HHT and data obtained with Wide Area Measurement System (WAMS). As general philosophy, the proposed NCF is defined as the ratio of the generators' node oscillation energy(NOE) and the total oscillation energy(TOE), related to a particular oscillation mode. The NOE and TOE is defined based on the intrinsic mode functions(IMFs), which is obtained with the application of the HHT method. In detail, the (individual) node oscillation energy is defined as the product of the node's oscillation amplitude and cosine of relative phase. And the TOE, is defined the positive (or reverse respectively) group total energy for the node in the positive or reverse respectively, where the positive (or reverse respectively) group total energy is the cumulative energy of all nodes in the positive(or reverse respectively) group. And the generator grouping is obtained according to the phase, which is defined for the IMFs obtained with the HHT method. Simulation results in 4-machine and 17-machine system show that the proposed algorithm for NCF is more effective than the existed algorithm. And furthermore, the active power signals have better performance than the angle signals.