Single current sensor technique in the DC-link of three-phase PWM-VS inverters. A review and the ultimate solution

This paper proposes an ultimate solution for reconstruction of three phase-currents in a PWM-voltage source inverter by one current sensor in the DC-link, and it gives a review of existing methods in literature and patents. The solution offers fully protection of the inverter including shoot-through of the DC-link, short-circuit of the output phases and earth faults with both low and high impedance. A special configuration in the DC-link can give such features. At the same time a new method to sample the DC-link current is proposed which both can eliminate disturbances from cables between an inverter and an induction motor, and it offers a true simultaneous sample value of all three phase-currents in the center of a switching period. The two methods are implemented in an experimental setup, and test results show that full protection is achieved and the three phase-currents are reconstructed precisely in the whole operating area