Field Oriented Control of AC drive

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

The motor control industry is (still) a strong, rapidly developing sector. The evidence of this statement is that newer and newer products are published on the market with the following features: improved dynamic behavior, cost reduction, power consumption reduction, power factor correction, and reduced EMI radiation. In order to meet these challenges, advanced control algorithms are necessary. Embedded control technology allows both a high level of performance and system cost reduction to be achieved.

Field Oriented Control (FOC) technique is one of the mostly applied algorithm to control the speed and the flux of a three-phase electric drive thanks to its high performance and the advances in the semiconductors technology in both power and signal electronics. Due to its many advantage FOC driven electric machines are applied from drive systems of low-cost home appliances, like washing machine, to high performance and expensive systems, like transportation or manufacturing automation.

The aim of this project is to investigate a sensorless FOC algortihm in simulation (in Matlab/Simulink environment) and on a real hardware as well. In the beginning of the project, I designed a printed circuit board which contains a three-phase inverter and some additional electronics to supply the microcontroller and process the signal of an encoder, but finally, no encoder was used. With this board I successfully drived a FEMIC squirrel-cage high-speed induction motor from a 90V DC bus. The control algorithm was realized on a dsPIC33FJ256MC710 microcontroller from Microchip. This controller is specially recommended for electric drives application by the manufacturer.

After giving a brief theoretical introduction into the field of AC motors and VFDs (variable frequency drives) I demonstrate the FOC algorithm in the 2nd chapter. Then, in the next chapter, I detailfully explain the operation of the applied speed estimator and controller algorithm. Still in the 3rd chapter, the simulation results are presented. In the 4th chapter, I demonstrate the design of the hardware and the embedded software, and I present the laboratory measurements. Finally, in the last chapter I evaluate the achieved aresults and propose some idea about possible further improvement of the project.


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