A new stator voltage third harmonic based direct field oriented control scheme

The paper presents a new and straightforward approach to compute instantaneous position and amplitude of the airgap flux in an induction machine using the stator voltage third harmonic component. Compared to previous direct field oriented control (DFOC) schemes also using the third harmonic voltage, the proposed method is simpler and able to exploit a reliable estimation technique practically unaffected by parameter variations. The scheme can be implemented in low and medium performance induction motor drive systems and is especially suited for low speed operations. It is presently used to develop DFOC drives with different features. Experimental tests are shown in order to practically confirm the expected features of the proposed system.<
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