%0 Journal Article
%T Direct Torque Control Induction Motor Drive with Improved Flux Response
%A Bhoopendra Singh
%A Shailendra Jain
%A Sanjeet Dwivedi
%J Advances in Power Electronics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/764038
%X Accurate flux estimation and control of stator flux by the flux control loop is the determining factor in effective implementation of DTC algorithm. In this paper a comparison of voltage-model-based flux estimation techniques for flux response improvement is carried out. The effectiveness of these methods is judged on the basis of Root Mean Square Flux Error (RMSFE), Total Harmonic Distortion (THD) of stator current, and dynamic flux response. The theoretical aspects of these methods are discussed and a comparative analysis is provided with emphasis on digital signal processor (DSP) based controller implementation. The effectiveness of the proposed flux estimation algorithm is investigated through simulation and experimentally validated on a test drive. 1. Introduction In a DTC induction motor drive, a decoupled control of torque and flux can be achieved by two independent control loops [1¨C3]. The steady state as well as the dynamic performance of the drive is closely related to the efficient implementation of these two control algorithm. There are few well-known methods to estimate these parameters. Most of them are voltage model based [3], where the flux and torques are estimated by sensing stator voltage and current. The methods based on voltage models are most preferable for sensorless drives since these methods are less sensitive to the parameter variations and does not require motor speed or rotor position signals. However, the estimation of stator voltage when the machine is operating at low speed introduces error in flux estimation which also affects the estimation of torque and speed in case of sensorless drive [4¨C11]. In a conventional DTC drive the basic-voltage-model-based flux estimation is carried out by integrating the back emf of the machine. A pure integrator has the following limitations.(1)Any transduction error in measured stator current due to offset introduces DC component and hence results in integrator saturation.(2)Integration error due to incorrect initial values. A commonly employed solution is to replace a pure integrator with a low-pass filter [12, 13], however it is achieved at the expense of deteriorated low-speed operation of the drive, when the operating frequency of the drive is lower than the cutoff frequency of the low-pass filter. Flux estimation based on the current model is most suitable for low-speed operation [14, 15], however it is a parameter dependent method, which require rotor speed or position. Thus parameter independent operation, which makes a DTC drive more robust and reliable compared to a FOC drive,
%U http://www.hindawi.com/journals/ape/2012/764038/