In this paper, a space phasor based current hysteresis controller for a three-phase voltage source inverter is proposed. The current errors are determined along three axes, which are orthogonal to the A, B, C phases, and the current error space phasor is held within a hexagonal boundary. The proposed controller does not require any computation of machine voltage vector and uses only those inverter voltage vectors, which are adjacent to the machine voltage vector for the entire range of operation. The region detection logic employed in the proposed controller ensures that, the vector (among the three adjacent vectors), which has the largest deviation in the opposite direction, is selected, for all the regions of the hexagonal boundary. A simple self-adapting logic is used to effect sector changes and smooth transition to six-step mode of operation is achieved. The proposed controller is implemented for a 5hp induction motor drive.
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