Research On The AC-Excitation Of Asynchronous Synchronous Generator's Protection

The Asynchronous Synchronous Generator (ASG) has two kind of forms of excitation structure, one is two phase of DC excitation and the other is three phase AC excitation. As rotor excitation structure and excitation control have the differences between ASG and traditional synchronous generator. The ASG has the advantages as the following: active power, reactive power and rotor speed can adjust independently under AC excitation. The ASG can not lose stabilization when absorbing mass reactive power. And the ASG can also be a variable speed constant frequency wind power. So the ASG has a wonderful applications and prospect in power industry and AC-electric transmission system. And its commercial application and protection studying are imperative under the situation. The AC-excited of asynchronous synchronous generator is emphasized in this dissertation.This paper has mentioned the AC-excited generator's protection scheme by analyzing traditional synchronous generator's single-phase grounding protection theory. That is according to the AC-excited generator's stator connection mode, there are neutral grounding system and non-neutral grounding system (include by arc-suppression coil grounding). As for the first one, use zero sequence voltage protection at terminals for mini-type AC-excited generator and analyze the AC-excited generator's mathematical modal in which the AC-excited generator was designed to connecting to the power system. As for the second one, use stator earth fault protection with 20 or 15 Hz voltage injection for good-sized AC-excited generator. This scheme avoid discussing the AC-excited generator's complex stator short-circuit harmonic.The AC-excited generator's excitation system is the generator's hardcore. The excitation system is different from the traditional synchronous generator's. Protecting the system is the most important work. From generator excitation system control theory start, study Generator excitation system hard, and analyze the AC-excited generator's excitation system fault feature. In the end, the protection scheme of the AC-excited generator's excitation system fault is designed according to the studying. The AC-excited generator needs three-phases excitation currents symmetry and smoothness, the author brings forward that if three-phases excitation currents are symmetry and smoothness is the main criterion to examine the fault. Considering the scheme's preciseness, various protection characters are analyzed at the same time. And the simulation model is built to check up the conclusion.Owing to the AC-excited generator's stator structure is as well as traditional synchronous generator's. After the theory of traditional synchronous generator's phase to phase short circuit and inter-turn short circuit of stator winding are analyzed. The author find that the protection scheme of the traditional synchronous generator's is fit for the AC-excited generator's. Therefore, the mature comparatively protection scheme can be use for the AC-excited generator.