Tham khảo tài liệu 'power quality harmonics analysis and real measurements data part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Electric Power Systems Harmonics - Identification and Measurements 49 Fig. 51. Final errors in the estimation using the two filters. 1. The estimate obtained via the WLAVF algorithm is damped more than that obtained via the KF algorithm. This is probably due to the fact that the WLAVF gain is more damped and reaches a steady state faster than the KF gain as shown in Fig. 50. 2. The overall error in the estimate was found to be very close in both cases with a maximum value of about 3 . The overall error for both cases is given in Fig. 51. 3. Both algorithms were found to act similarly when the effects of the data window size sampling frequency and the number of harmonics were studied 6. Park s transformation Park s transformation is well known in the analysis of electric machines where the three rotating phases abc are transferred to three equivalent stationary dq0 phases d-q reference frame . This section presents the application of Park s transformation in identifying and measuring power system harmonics. The technique does not need a harmonics model as well as number of harmonics expected to be in the voltage or current signal. The algorithm uses the digitized samples of the three phases of voltage or current to identify and measure the harmonics content in their signals. Sampling frequency is tied to the harmonic in question to verify the sampling theorem. The identification process is very simple and easy to apply. Identification processes In the following steps we assume that m samples of the three phase currents or voltage are available at the preselected sampling frequency that satisfying the sampling theorem. . the sampling frequency will change according to the order of harmonic in question for example if we like to identify the 9th harmonics in the signal. In this case the sampling frequency must be greater than 2 50 90 900 Hz and so on. 50 Power Quality Harmonics Analysis and Real Measurements Data The forward transformation matrix at harmonic .
