A multi axis space phasor based current hysteresis controller for PWM inverters

摘要

In conventional three phase current hysteresis controllers, the current error along the three phase axes are independently controlled. This will result in random selection of switching vectors causing high inverter switching losses. In this paper, a space phasor based multi-axis current hysteresis controller is proposed, in which the current errors along the axes jA, jB, jC (which are othogonal to the A, B, C phase axes respectively) are monitored. The current error boundary in the space phasor domain is a hexagon. The proposed control scheme can be implemented using simple look up tables. The inverter switching states from the look up table are selected based on only current errors (delta currents), along the orthogonal axes to the A B C axes, respectively. When compared to other multi-level current hysteresis current controllers, the advantage of the present scheme is that, only the adjacent inverter voltage vectors close to the motor back emf space phasor voltage, is only used for the inverter switching, for the entire speed range. In the present scheme, the selection of the inverter voltage vectors for PWM switching is achieved by, without any need for computing the machine back emf vector, for the full speed range of the drive system. The proposed scheme is self adapting, as far as the motor space phasor voltage is concerned, and also maintains the controller simplicity and quick response features of a hysteresis current controller. The scheme is simulated and also experimentally verified.