Review of Vector Control Systems

Abstract

Both the direct and indirect field orientation schemes presented in Chapter 4 have specific advantages and disadvantages. The direct scheme requires use of flux sensors installed inside the motor and spoiling the ruggedness of the machine. Instead of the delicate Hall sensors, the so-called search coils can be used which allow the airgap flux measurement to be performed by integrating the induced voltage. These, however, are useless at low speeds, which result in an excessively long integration time. The indirect approach to field orientation is based on sensing the position of the rotor, again a frail arrangement, and, most of all, it is very sensitive to motor parameters. Incorrect knowledge of these leads to significant deterioration of the operation of the drive system. Therefore, a tremendous amount of research has been conducted to develop viable vector control systems for induction motors in commercial applications. This effort is far from being concluded, and only time will show which of the large variety of solutions proposed every year in scores of papers will survive the test of practical implementation. In effect, only a general review of the existing vector control systems can be attempted in this book.