Speed Estimation at Coasting Condition in a Sensorless Induction Motor Drive for Railway Vehicle Traction System

철도차량 추진 제어를 위한 유도전동기 센서리스 구동 시스템에서 타행운전시 속도 추정

In this paper, a speed estimation method at coasting operation in an induction motor speed sensorless control for railway vehicle traction systems is presented. At coasting operation, there is no information obtaining rotor speed since all switches of an inverter are turned off. The inverter frequency should be synchronized with the rotor frequency for repowering at coasting condition. The proposed method injects DC current to the induction motor during a short time, then the flux angle and rotor speed needed for control can be estimated rapidly.