Authors: Bheemaiah Chikondra, Utkal Ranjan Muduli and Ranjan Kumar Behera
The multi-phase machine (MM) drives are best suitable for safety-critical applications due to its inherent fault-tolerant capability. The fault-tolerant operation of MM drives is challenging and necessary for applications such as off-shore ship propulsion, high-way electric vehicles, and more electric aircraft. A two-level voltage source inverter (VSI) fed five-phase induction motor (FPIM) drive has been considered for the post-fault performance assessment. In this paper, an improved fault-tolerant direct torque control (DTC) technique is proposed for the FPIM drive based on virtual vector (VV)s assessment under the open-phase fault condition. The theoretical analysis is carried out to investigate the impact of VVs on the change in torque as well as flux response at different speeds and loading conditions. Based on this analysis, a modified lookup table, flux, and torque hysteresis bands are designed to improve the functioning of the fault-tolerant DTC of FPIM drive. The FPIM drive performance is analyzed and tested experimentally with an open-phase fault. Studies have confirmed the reliability and superiority of the proposed DTC controller over existing post-fault solutions. In addition, the robustness of the FPIM drive at steady-state and dynamic operating conditions is evaluated from the given results, including the transition from pre-to-post fault operation.
Based on the literature, the objective of this chapter is defined. The behavior of the VVs in the fault-tolerant operation is unpredictable and not yet specified in the literature, which is a major objective to the proposed article. Hence, an attempt is made to find the behavior of VVs on flux and torque under the post-fault operation, by which the modified lookup table, flux, and torque hysteresis bands can be designed.
The key contributions from the paper is listed as follows:
- Theoretical analysis is developed to determine the effect of each VV on the change in flux and torque response for post-fault control of the FPIM drive at varying speeds and loading conditions.
- From the VVs assessment, the entire αβ plane is divided into 16 sub-sectors from available 8 sectors for the effective design of lookup table.
- Besides, the torque hysteresis band (THB) and flux hysteresis band (FHB) are selected under the maximum change in torque and flux response by analyzing the individual effect of available VVs.
- A modified DTC control structure with torque, flux, and speed estimation is implemented for both pre and post-fault operations.