3. Oscillatory Parameters Computation Based on Improved HHT

In the point of operation, the responses of real bulk power system are dynamic and time-varying owing to the influences of load variations, topology changes, and control actions. It is necessary to monitor and calculate the instantaneous oscillatory parameters so as to provide an optimal control strategy. As a nonlinear and nonstationary signal processing approach, Hilbert–Huang transform (HHT) which contains Empirical Mode Decomposition (EMD) and Hilbert transform (HT) has been widely utilized to calculate the amplitudes and frequencies of the single LFO signal. The decomposition ability of EMD provides the condition for HT and HT extends the application fields of EMD. However, the further applications in power system are limited by the inherent shortcomings of HHT, such as the end effects (EEs) and mode-mixing in the process of EMD as well as Gibbs phenomena in traditional HT. In this chapter, the shortcomings of HHT are analyzed and an improved HHT is proposed to determine the oscillatory parameters of single measured signal.