||Synchrophasors Measurement Based Mode Detection and Damping Estimation in Power System using FFT Continuous Wavelet Transform Approach
The thesis carries out the estimation of damping as well as the frequencymode of inter area oscillations in the range of 0.1 to 1.0 Hz. This belongs underthe topic of angle stability management of power systems. Previously some otherstudies had been conducted in this area at which most of them employed themethods such as the least squares, Yule-Walker, autoregressive (AR),autoregressive moving average (ARMA), the Kalman filter and the subspacemethod. Another research also had been conducted which based on Fast FourierTransform (FFT) analysis individually, the damping ratio and frequencyoscillation were estimated from eigenvalue of the matrix associated to a SingleMachine Infinite Bus (SMIB) model. An output-only-based simplified oscillationmodel was developed to estimate the characteristic of inter-area power oscillationbased on extracted oscillation data. However, this previous method did notexplain how to calculate damping ratio without considering any simplified model.Furthermore, the behavior of the signal during certain time of analysis could notbe described.This thesis promotes a novel approach in analyzing PMU data based onFast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT)algorithm. Then proceed by demodulating the slicing signal at a particular peakand ridge of the signal using a decrement technique. The approach applied in thisthesis can be classified into the non-parametric approach, where it works directlyon the data. The damping calculation method in this thesis emphasized on theaccurate and robust damping estimations which was proved by attempting thesimulation towards various level of signal to noise ratio (SNR).To verify the outcome of this method a synthesized signal contains ofthree ringdown modes representing a real signal from PMU was analyzed. Theresults were compared to the given parameters and it was clearly shown that thismethod gave the result within an acceptable range of error. Additionally, theacceptability of this method was also verified by comparing to the result ofeigenvalue-based calculation on a standard power system model. The simulationindicated the results of the two approaches fitted each other means this FFT-CWTis workable to assess the damping ratio of a small signal oscillation in powersystem. The advantage of this method is no prior data of the system required;hence this approach is very applicable in the power system where gathering datafrom the network is not attainable.This thesis also elaborated the application of wide area signal recorded byPMU, refined by the FFT-CWT method, for controlling the oscillation damping ofpower system. The simulation showed the application of wide area signal as aninput to the damping controller has a great prospective to countermeasure the interarea oscillation in the system.
九州工業大学博士学位論文 学位記番号:工博甲第413号 学位授与年月日:平成28年3月25日
1. INTRODUCTION|2. SYNCHROPHASOR MEASUREMENT AND THE METHOD OF ANALYSIS|3. FAST FOURIER TRANSFORM AND CONTINUOUS WAVELET TRANSFORM APPROACH|4. APPLICATION OF THE APPROACH FOR MODE AND DAMPING CALCULATION|5. WIDE AREA SIGNAL DAMPING CONTROLLER|6. CONCLUSION AND FUTURE WORK