A fault investigation and optimization with constant frequency electrical angle start method of LCI

Abstract

Load-commutated inverter (LCI) are the key starting device of wound-field synchronous motor. By detecting the rotor position and inputting a variable frequent current to the stator windings, the LCI can drive the motor from standstill to a given speed. Thus, rotor position detecting method comes to be the key techniques, but at the ultra-low speed period, the motor's terminal voltage is too low to accurately sampling and is vulnerable to the interference, which brings risks to the variable frequency driving. In this paper, through analyzing the principles of LCI and a running fault problem, a constant frequency electrical angle control methods is introduced to solve the difficulty of detecting the rotor position in the low speed period. A 300MW synchronous machine driven with a 19MW LCI are experimented in MATLAB and RTDS systems, the results show that the proposed control strategy can realize soft-start of the wound-field synchronous motor without detecting rotor's position.