Geir Kulia

Signal Analysis Lab

Continuous biological signals, like blood pressure recordings, exhibit non-linear and non-stationary properties which must be considered when analyzing them. Heart rate variability analyses have identified several frequency components and their autonomic origin. There is need for more knowledge on the time-changing properties of these frequencies....

Nonlinear and/or nonstationary properties have been observed in measurements coming from microgrids in modern power systems and biological systems. Generally, signals from these two domains are analyzed separately although they may share many features and can bene�t from the use of the same methodology. This paper explores the use of Hilbert-Huang...

The paper addresses the impact that time varying angular frequencies observed in electrical signals can have on the calculation and separation of components from the instantaneous electric power signal. Instantaneous power theories provide various methods for calculating the instantaneous power components in an electrical network. These methods are...

Passive loading is a suboptimal method of control for wave energy converters (WECs) that usually consists of tuning the power take-o� (PTO) damping of the WEC to either the energy or the peak frequency of the local wave spectrum. Such approach results in a good solution for waves characterized by one-peak narrowband spectra. Nonetheless, real ocean...

Passive loading is a suboptimal method of control for wave energy converters (WECs) that usually consists of tuning the power take-off (PTO) damping of the WEC to either the energy or the peak frequency of the local wave spectrum. Such approach results in a good solution for waves characterized by one-peak narrowband spectra. Nonetheless, real ocea...

This paper presents an analytical method developed to explain the mechanism of harmonic transfer between the ac and dc sides of a single-phase inverter in a PV microgrid. The model explains how the feed-forward of the current from the ac side of the PV-inverter into the control system, causes even harmonics on the dc voltage. It further shows how t...

This paper describes a platform for obtaining and analyzing real-time measurements in Microgrids. A key building block in this platform is the Empirical Mode Decomposition (EMD) used to analyze the electrical voltage and current waveforms to identify the instantaneous frequency and amplitude of the monocomponents of the original signal. The method...

A brain computer interface (BCI) or brain machine interface (BMI), is a direct communication pathway between the brain and an external device. This report describes a Brain Computer Interface(BCI) system based on the EEG recordings of the Emotiv EPOC headset and the post recording procedures with python in Linux environment. The BCI system processe...

This thesis presents a validation study based on data analysis aimed at identifying the cause of atypical behavior observed in a microgrid’s data. The data of a stand- alone PV microgrid in Bhutan is analyzed. The analysis of the voltage waveform distortions found in the data is utilizing the Hilbert-Huang Transform (HHT) and periodograms. The Hil...

This short communication shows a case in which instantaneous frequencies are detected on synthetic signals by both Wavelet (WT) and Hilbert Huang Transform while Fourier Transnsform (FT) is not effective in identifying them. The selected synthetic signal is an example of how using FT in electric power systems with time varying frequencies, can misl...

This paper describes a platform for obtaining and analyzing real-time measurements in Microgrids. A key building block in this platform is the Empirical Mode Decomposition (EMD) used to analyze the electrical voltage and current waveforms to identify the instantaneous frequency and amplitude of the monocomponents of the original signal. The method...

This article presents the applicability of Permutation Entropy based complexity measure of a time series for detection of fault in wind turbines. A set of electrical data from one faulty and one healthy wind turbine were analysed using traditional FastFourier analysis in addition to Permutation Entropy analysis to compare the complexity index of ph...