Study On The Renovation Of Generator Excitation System In Ankang Hydropower Station

This paper took generator excitation system transformation of Ankang hydropower station as main research contents,according to excitation system roles in power system and actual work needs of Ankang hydropower station.Because the static excitation system of AC separately excited thyristor existed problems,such as poor reliability,complex structure,backward technology and imperfect function,it designed a new excitation system for solving.This paper discussed around the problem of excitation system transformation,analyzed four aspects successively:determination of transformation scheme,system modeling and stability analysis,device selection calculation and field test,and made conclusion as three points.1)Based on research literature and practical problem analysis related to excitation control theory,technology and system modeling,it came up with the overall scheme of self-shunt excitation system,which was able to bring advantages,such as high system reliability,fast voltage response and small unit vibration.2)Through the comparison of various excitation control modes,it designed the structure of AVR+PSS excitation regulator for Ankang hydropower station,and established the corresponding mathematical model of excitation system.Then it compared power grid stability between before and after excitation system transformation through PSASP software.Furthermore,it found that power grid stability would be slightly changed and system damping will be reduced under two kinds of fault conditions,when reforming the excitation system of 1,2,3 and 4 units respectively.Meanwhile,the damping ratio of the oscillation mode with the oscillation frequency of 0.86hz was 7.06%,and the system damping was effectively improved,when PSS2A is used in all 4 units.3)The field tests of the modified excitation system,which including function simulation test of the regulator in static state,automatic boosting and inversion deexcitation test at no-load,over excitation and under excitation test during grid connection,were carried out.All the test data met the requirements of the regulations and the functional requirements of the excitation system.