Investigation of Frequency Controlled Electric Drive with Control Signal Limitation by the Frequency Controller

The paper is concerned with the automatic electric drive characteristics taking into account its coordinate limitations, in particular, frequency converter input voltage. A model developed in MATLAB environment in SIMULINK application was used to carry out the research work. The model includes a frequency converter, an asynchronous motor and a speed control system with vector control where the variables are represented both in fixed and rotating coordinate systems. To analyse the electric drives with vector control, the method for structural modeling was used. The model takes into account the voltage limitation at the current controller output in the speed control system because it, in fact, limits the amplitudes of input three-phase voltages in the frequency converter. Automatic electric drive dynamics is studied in the acceleration and load surge modes. When the changes in the electric drive resistance moment are significant, the increase in the voltages at the current controller output is possible, which exceeds the voltage capacity for the frequency converter input. In this case, the speed control system opens and causes electric drive malfunction. In order to adjust the drive operation in this mode, it was proposed to decrease the voltage set point at the input of the flux linkage controller. The simulation results confirm the efficiency of this solution.