Identifier of Stator Flux Linkage in the Vector Control System of Doubly Fed Machine

2024;
: pp. 84 - 94
1
Dniprovsk State Technical University
2
Dniprovsky State Technical University, Department of Electrotechnical and Electromechanical
3
Vasyl’ Stus Donetsk National University

Currently new structures of sensorless control systems for AC electric drives are being actively developed. Reducing the number of sensors reduces the cost of the control system, simplifies its operation and increases the reliability of the electric drive. To build a vector control system, you first need to find a way to determine the spatial position of the reference vector. In field-oriented control systems the flux vectors of the stator, rotor or air gap are taken as reference. In a field-oriented control system for a doubly fed machine (DFM) the stator flux linkage vector is taken as the reference vector. A well-known approach to identifying the spatial location of the stator flux linkage reference vector is to integrate the EMF of the stator windings. However integrators without negative feedback accumulate an error at their output, which can lead to a loss of stability of such flux linkage identifiers. The article proposes differential equations for the identifier of the stator flux linkage reference vector in the vector control system of a doubly fed machine. These equations are solved in real time with respect to the projections of the flux linkage vector onto the orthogonal axes of the rotor. By analyzing the coefficients of the characteristic equation of this identifier its asymptotic stability is proven. Stability conditions are obtained that relate the properties of the electric machine vectors and their relative positions. The use of such an identifier in the control system allows one to abandon the use of flux linkage sensors. Together with the identifier the control system uses two vector analyzers, the information from which is sufficient to calculate the rotor angle of a doubly fed machine and thereby exclude the rotor angle sensor from the control system. In signal microprocessors it is possible to implement the developed control system in the form of program code. The dynamics of an electric drive with the proposed stator flux linkage identifier as part of a vector control system was studied using the method of mathematical modeling.

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