Efficiency optimization of an induction machine using constant optimal flux control

Abstract

This thesis presents a simulation study of efficiency optimization on Variable-Speed Induction Machine (VSIM) using Constant Optimal Flux (COF) control technique using Matlab/Simulink software. The study covers both motoring and generating modes of a 1.1kW Squirrel-Cage Induction Machine (SCIM) to improve the entire system performance that uses constant V/f Scalar Control (SC) method. SC method is the pioneer of controlling variable speed IM, thus, it is widely used in most of the IMs applications. However, due to discovery of modern and high performance with complex design of VSIM controllers, the SC method is getting less attention in research and development field of controlling IM. Therefore, in this study, the COF control strategy is proposed to improve the efficiency of conventional SC method to the optimum level by providing optimal flux to the IM. The optimal flux is obtained by implementing the Loss Model based control technique as it could reduce the copper power loss for each of operating speed along the operation. To ensure that the optimal flux has high capability to improve the performance of IM, an approach called as Maximum Torque per Ampere is adapted to ensure that the torque capability of the machine is maximized during the operation. From the simulation results obtained in the study, the proposed COF control technique indicates satisfactory results over the conventional constant V/f in open-loop and closed-loop SC systems with better dynamic response under transient and steady-state conditions. The findings also show that for the proposed COF control strategy, power loss is successfully reduced and it improves the efficiency of IM in both motoring and generating conditions. Besides, the findings also indicate that the proposed control strategy provides a significant power saving during the high speed operating range. As the implication, a simple design and higher efficiency of SC technique has been developed in order to improve the effectiveness of the existing conventional constant V/f SC method.