Fault Tolerant Operation of Motor Drive Fed by Dual Inverter Focusing on DC-Bus Battery Failure

A fault tolerant operation of the DC-bus battery in the dual inverter motor drive feeding an open-end winding motor is described in this paper. The dual inverter motor drive studied in this paper has a battery and a capacitor in parallel across the DC-bus of each inverter, and it is assumed that the battery across the DC-bus of one of the inverters is separated. The dual inverter motor drive has the redundancy of the switching state, which means that the particular voltage vectors can be generated with the several redundant states. In the fault tolerant operation, the failed inverter is operated with the capacitor instead of the failed battery, and the capacitor voltage is controlled at constant value by using the redundant switching state with a space vector modulation (SVM). In particular, the capacitor voltage of the failed inverter is required to be regulated at a half of the battery voltage of the normal condition inverter, in order to utilize the redundancy of the switching state. On the other hand, in the normal condition, the battery voltages of both inverters are same to expand the operation region of the dual inverter system, because the system can generate the voltage vector to the motor by adding the output voltages of two inverters. Therefore, it is necessary to discharge the capacitor voltage smoothly up to a half of the battery voltage of the normal condition inverter, immediately after the failed battery is separated. In this paper, the switching over techniques from the normal condition to the fault tolerant operation of the DC-bus battery with the SVM in the dual inverter motor drive are proposed. The proposed techniques are examined through several computer simulations and experimental tests.