| Abstract |
Direct self-control (DSC) of an inverter-fed induction machine is a signal processing technique based on two-level hysteresis controllers of the machine flux and torque. The attractiveness of DSC is its simplicity and high dynamic performance even using high power, low switching frequency converters . One disadvantage of DSC, however, is that the output inverter current is not sinusoidal, containing harmonic components typical of those in six-pulse, square wave inverters. In the previous works of the author two different techniques which allow reduction of the above distortions have been published. This reduction was achieved by: flux trajectory corner folding or by partial replacement of zero vectors. In the paper an alternative method is proposed which is based on processing a stator flux trajectory. The method offers possibility of flux self-compensation at low speed. It is shown that this method can be easily extended to drives with a discrete PWM which don't use zero vectors. It is also shown that by dividing a stator flux trajectory into two areas, in which different hysteresis width of a torque controller ls applied, reduction of motor current active distortions at speed close to nominal can be achieved. |
