Time-frequency single-phase power components measurements for harmonics and inter-harmonics distortion based on wavelet packet transform; Part II: case studies and results

This is the second part of a two-part study concerning power components measurement in the time-frequency domain using Wavelet Packet Transform (WPT). Four case studies are presented comparing the recommended power components that are contained in the IEEE Standard 1459-2010 [1] based on Fourier Transform approach, versus power components suggested by the newly developed time-frequency 'in-phase quadrature' approach using Wavelet Packet Transform; the latter derived in the first part of this two-part study. The first two cases are simulated cases in the Matlab environment to include both harmonic and interharmonic distortion, while the other two cases are real data cases acquired from computer loads and Adjustable Speed Drives. The values of the recommended power components using both approaches are compared and the results indicate that the time-frequency 'in-phase quadrature' approach using WPT is more accurate, especially in the presence of interharmonics. Both time and frequency information is preserved, allowing representation of the power components in a time-frequency spectrum. This provides a complete performance picture compatible with present practical load configurations.