FPGA Implementation of a DB – DTFC Scheme for Induction Machines

Abstract: Induction machines have been used in a wide range of applications due to its robustness and its low price. These characteristics make the induction machine a suitable option for industrial and home environments especially for those applications where the required speed is constant and the load does not change drastically. As an alternative to the induction machine, the synchronous machine, particularly the Permanent Magnet machine has been used as well in a wide range of applications, as it is the case with electrical traction systems for different vehicles. But the recent increase in the price of magnets and the difficulty to find a reliable source for massive production, have become an important reason to try to move the market to magnet-free alternatives, such as reluctance and induction machines. However, controlling an induction machine has been a difficult task since its invention, especially during highly dynamic regimes, where the required torque/speed changes constantly. In order to solve this problem several methods have been developed over the years, the most used are field oriented control and direct torque control. Both methods use the torque and the magnitude of the magnetic flux as controlled variables. But, even if they provide an acceptable response, they still present some limitations as torque ripple, current ripple, overshot, etc. In order to improve the performance of the induction machines when working in demanding regimes numerous improvements have been made to the existing control methods, and also new methods have been developed. One of the methods recently developed is called Deadbeat Direct Torque and Flux Control. This method has been developed at the Departments of Mechanical Engineering and Electrical and Computer Engineering, University of Wisconsin, Madison. The DB-DTFC is presented as an alternative that promises to reduce considerably the lacks presented in the previous methods. In principle this new method is supposed to provide an instantaneous response without overshoot or torque ripple under perfect conditions. According to all the bibliography found, this technique has been only implemented in a micro controller and exclusively by the mentioned research group. This makes the thesis even more interesting since it may be the second documented attempt to implement such system and the first time it is done on an FPGA.