Ship Power Quality Detection based on Improved Hilbert-Huang Transform

Hilbert-Huang Transform (HHT) and its improved method are introduced to detect and analyze power quality in ship power system for the first time, in this paper. The HHT method is used to detect surge current, voltage sag and swell, voltage interruption, etc. of the ship power system. By means of Hilbert-Huang transform, Beginning time, ending time, time-frequency, timeamplitude of the disturbance signal can be obtained accurately. Because the fundamental energy is bigger than other single harmonic's, mode mixing occurs when using empirical mode decomposition (EMD) method to decompose harmonic signal in ship Power system, and consequently, each single harmonic component cannot be effectively extracted from the complex original signal. The improved HHT method based on Fourier transform is used to solve the mode mixing problem in this paper. By means of the improved HHT method, complex harmonic signal can be decomposed into single harmonic component, and timeamplitude and time-frequency of harmonics can be obtained accurately. In MATLAB/Simulink platform, harmonic source model is established according to characteristics of the ship power system to simulate harmonic current signal. And the improved HHT method and wavelet packet transform are applied in analyzing the harmonic current signal. Simulation results show that the improved method has better performance in harmonics analysis than wavelet packet transform.