Application of the voltage loss ride-through technology in medium voltage AC-AC converter

This paper compares two kinds of speed measurements and puts forward the torque current estimation method to estimate motor speed, therefore the motor speed can be accurately estimated by this method without additional hardware. With the application of the method, the function of medium voltage loss ride-through can be achieved in medium voltage cascade converter system. That includes the determination of torque current, the V/f setting curve, results judgment of frequency search, and etc. After tests in laboratory and field application verification, the function of medium voltage loss ride-through based on the torque current estimation method can be accomplished successfully, and improves the operation reliability of the converter application. Moreover, that promotes the function expansion of the medium voltage converter system (such as switch over function between the converter power supply and industry power supply).