Mathematical Model of the Active Rectifier under Unbalanced Voltage Operating Conditions

Abstract

Asymmetric voltage dips lead to disconnection of the main drives (MD) mills and as a consequence to operational delays. Modern MD is often performed on the basis of synchronous motors and frequency converters, consisting of active rectifier (AR) and voltage source inverter.  Control systems of active rectifier usually not adapted to asymmetry of voltage or when the asymmetry AB passes the diode mode. Analysis of work MD 2000 cold rolling mill showed that when voltage asymmetry AR enters to the diode mode. However, this method is not very effective because often occur disconnection MD and equipment downtime. Since the known mathematical models of the AR does not allow to study the operation of AR in the diode mode, a mathematical model that allows it to do. Using the resultant model analyzes work MD mill 2000 at a voltage asymmetry in the absence of AR adaptation to unbalance in the case of switching the diode AR mode as well as in the case of feedforward control of negative sequence of current. The results show that AR with feedforward control current negative sequence most stable operating in asymmetrical modes.