International Review of Electrical Engineering (I.R.E.E.), Vol. 12, N. 5 ISSN 1827- 6660 September – October 2017 Copyright © 2017 Praise Worthy Prize S.r.l. - All rights reserved https://doi.org/10.15866/iree.v12i5.12857 440 440 440 Improvements in SVM-DTC of Induction Motor with Fuzzy Logic Controllers Using FPGA Sudheer H., Kodad S. F., Sarvesh B. Abstract – Direct torque control (DTC) is a simple and robust control algorithm for high performance industrial applications. The conventional DTC suffers from major drawbacks like high torque and flux ripples, variable switching frequency, current distortions during changes in switching sector and poor performance during low speed operations. The problem of the variable switching frequency and the reduction in torque and flux ripples can be achieved using space vector modulation based direct torque control (SVM-DTC). The dynamic performance of the SVM- DTC is improved by replacing the constant gain PI speed, flux and torque controllers with fuzzy controllers. In this paper, both SVM-DTC with PI controller and fuzzy controllers are implemented using FPGA. The complete VHDL code for both DTC with PI and Fuzzy controllers is initially developed and simulated and then synthesized using Xilinx ISE 14.3 design tool. The complete developed code of the proposed algorithm is implemented on Spartan 6 XC6SLX25 board. The experimental results depict that an improved dynamic response of the induction motor is achieved in the SVM-DTC of the induction motor using fuzzy logic controllers. Copyright © 2017 Praise Worthy Prize S.r.l. - All rights reserved. Keywords: FPGA, DTC, Spartan 6, PI Controller, Fuzzy Logic Controllers Nomenclature V abc Voltages of a, b and c phases φ sd , φ sq Stator flux d and q-axis components R S Stator resistance J Moment of inertia T e * , T e Electromagnetic reference and actual torque Reference and actual stator flux θ Stator flux angle P Rated Power of Motor in kW DTC Direct torque control FPGA Field programmable gate array PWM Pulse width modulation K P , K I Proportional and Integral controller gain SVPWM Space vector pulse width modulation FLC Fuzzy logic controller QEP Quadratic encoder pulse IM Induction motor I. Introduction In 1980’s, the direct torque control of induction motors was developed by I. Takahashi and T. Noguchi, in which the stator flux and the electromagnetic torque of the induction motor is controlled by a selection of the optimal switching vector of VSI using a switching table [1]. Direct self-control was proposed by M. Depenbrock, in which hysteresis controllers are used for the duration of the application of voltage vectors to VSI [2]. Over the last decade, several techniques have been adapted to improve the performance of conventional DTC (CDTC) [1]-[34]. The major disadvantage of variable switching is eliminated in space vector modulated- direct torque control (SVM-DTC). Space vector modulations based direct torque control using various techniques are proposed in [3]-[6]. The review of different control schemes is given in [7]. Thus, based on this comparison, the SVM-DTC is the best solution for the implementation of direct torque control over a wide speed range with constant switching frequency. Compared to switching table based DTC, DSC experimental implementation of SVM-DTC is simpler as it does not require high switching frequency due to the absence of hysteresis controllers and constant switching frequency. Many attempts have been made to improve SVM-DTC like the use of discrete SVM in [8], the use of multi-level inverters in [9]-[11] and the feed-forward approach for stator-flux-oriented DTC in [12]. The use of the fuzzy logic controller replacing hysteresis controllers and the switching table is given in [13]-[14], using the neuro-fuzzy controller as proposed in [15]. The use of the fuzzy duty ratio controller for a reduction in torque and flux ripples is given in [16]. Few researchers proposed improvements in DTC performance using Adaptive PI controller, turning of PI gains using AI techniques, Neuro-Fuzzy controllers, fuzzy controllers or hybrid controllers [17]-[22]. The fuzzy controller is used instead of a conventional three level hysteresis torque comparator to minimize the torque ripple, as proposed in [23]-[24]. The use of