Executive Summary : | Induction motor (IM) drives are undoubtedly one of the most important candidates for different variable speed industrial applications. This is due to its robust construction, ample availability in ratings of different ranges, less maintenance requirement and comparatively low and stable cost. More importantly, the availability of its different components indigenously leads to the choice of IMs more suitable in electric vehicle (EV) applications in Indian scenario unlike the permanent magnet motors. Conventional field oriented control (FOC), direct torque control (DTC) and of late model predictive control (MPC)-based speed control strategies are generally used for high performance speed control applications of IM drives.
However, the satisfactory performance of drive systems used in any applications is immensely reliant on the faithful working of all of its major components. Hence, on-line fault detection and its isolation in drive systems is imperative nowadays. Major failures in drive system in this regard are: converter fault, machine fault and sensor fault. Malfunctions or failures of different sensors dedicated either for speed or current or voltage measurements are considered as sensor fault. In IM drive system, current sensors are mostly disposed to the failure. Sensor failure refers to mechanical damages or electrical disruptions of "Hall sensing device". In addition, any wrecked or slack connection, interrupted communication, certain hardware malfunctions causing impaired reproduction of operating current for the period of the drive operation are also considered as sensor failure. However, the research work in this regard is mostly devoted to FOC of IM drive. Although a few literatures report fault-tolerant control (FTC) of DTC of IM drive, but these are discussed with reservations. Moreover, most of the research works in this regard suffer from the shortcomings like: (i) applicable to a particular control environment mostly for FOC, (ii) involves computational complexity, and (iii) demands fast acting processors which are costly.
Under these circumstances, the present research work intends to introduce a common but simple approach for current sensor FTC of IM drive in three different control regimes such as FOC, DTC and finite-control-set (FCS)-MPC so as to avoid sudden catastrophic drive operating condition. The work intends to validate the scheme in a 5.2 kW IM drive with Spartan 6 FPGA development board.
The need of enhanced reliability of IM drives in different applications is accelerating the requirement to increase their level of fault-tolerance. Emergency halt is not necessarily the best way to react if component fails. In some cases, it is even more hazardous. Hence, soon after the diagnosis of current sensor failure, on-line isolation of the faulty sensor and reconfiguration of control scheme by proper estimation is very much essential to avoid catastrophic failures of IM drive systems used in any applications. |