Study Of Operation Of Rotating Rectifying Components In Brushless Exciter In The Modes Of Forced Excitation And Short-circuit

Rotating rectifier is one of the most important parts in the brushless exciting system, the normal operation of which must be assured. When the rotating rectifier is in the abnormal situations, such as over-current, over-voltage and so on, although there is protecting equipment to protect the power diodes, it is very difficult not to damage the diodes at all (open-circuit or short-circuit). When the power diodes of the rectifier are damaged, there should be an alarm at once, and especially when a diode short-circuits, the fault should be removed immediately. However, short-circuit don't be removed in time somehow, and the system will be damaged heavily. The analysis of the performance of all rectifying components in the situation of diode short-circuit is one of the problems studied in the paper.The brushless exciter in some power state is taken as research background in the paper. Firstly, turbo-generator exciting ways, the development of brushless exciting system and the domestic and foreign present research situation for the system of synchronous machine with the rectifier are introduced. Then the method of mode classification is used, simulating and analyzing the operation of the rectifier components in the rating and forced-exciting conditions. The method classifies the rectifier into several rectifying working patterns and operating modes according to its operating conditions, and determines mode converting paths and converting conditions during the period of each rectifying working pattern. When simulating, it judges rectifying working patterns firstly, determines the operating modes according to the converting conditions, and then the state equations of all modes are derived to make the simulation and calculation. Because it is very difficult for the method of mode classification to simulate the situations of diode short-circuit, the PSB model of brushless exciter and synchronous machine is established, with the rectifying block of the MATLAB software used, so as to omit the determination of rectifying working patterns and operating modes in the method of mode classification. The PSB (Power System Block) model simulates the operating of rectifying components in the conditions of diode short-circuit and two-phase short-circuit and three-phase short-circuit of the exciter armature. Finally, the PSB simulates some kinds of conditions, considering the diode buffer circuit.The research in the paper is significant to the analysis of the influence of exciter rotating rectifying component faults on machine operation and all kinds of performances, meanwhile providing an effective basis for the development and design of brushless exciting system.