Abstract
<jats:p>In this paper for the control system of a doubly fed machine (DFM) previously proposed by the authors, a discrete extended Kalman observer is synthesized in order to develop a sensorless relay – vector control system for the DFM with two extremum regulation loops. The Kalman observer is of relatively high order because in addition to identifying the reference stator flux linkage vector and rotor angular speed – which is sufficient for induction machines (IM) with a squirrel-cage rotor controlled through the stator – this observer also estimates the rotor position angle and the external disturbance, represented by the static load torque applied to the DFM shaft. A second feature of the proposed Kalman observer lies in the inclusion of the stator voltage vector projections onto the orthogonal rotor-related axes within the observer’s state matrix. Thus, these projec-tions are computed as state variables rather than external inputs, with the only external control actions being the voltages applied to the rotor circuit of the DFM. In the rotor and stator reactive power channels optimization of the DFM’s energy performance is achieved under steady-state operating conditions. The standard Kalman filtering algorithm is applied here to a deterministic system to enable the identification of all necessary process variables within a single observer. The Kalman observer operates stably because the measured rotor currents of the DFM, from whose estimation errors the corrective feed-backs are formed, contain high-frequency pulsations under direct relay control; these pulsations are perceived by the ob-server as random measurement noise. Through mathematical modeling of a DFM with a fan-type mechanical load on the shaft, the high quality of speed regulation and the achievement of extremal energy performance values in steady state have been theoretically confirmed for the sensorless control system based on the proposed Kalman observer. References 21, figure 1.</jats:p>