This paper proposes a sensorless control scheme for synchronous reluctance (SyR) motor drives based on the direct-flux vector control (DFVC) method. The control operates in stator-fluxoriented coordinates, using constant switching frequency. A hybrid position and speed observer is proposed, based on the combination of the active flux concept and high-frequency signal injection and demodulation. The two methods are fused together to form a unique position and speed estimate signals, with seamless transition between the two models based on reference speed. The proposed observer covers a wide speed range, from standstill operation at full load to flux weakening (FW). Furthermore, it is inherently immune from position estimation error caused by cross saturation, as proven mathematically and experimentally. The motor is operated according to the maximum torque per ampere (MTPA) law. Specific issues related to MTPA around zero torque are addressed in this paper. The proposed control technique extends the range of application of the DFVC to encoderless drives, and can be usefully adopted in those applications where both zero-speed and FW speed range operations are necessary, such as home appliances, or automotive and aerospace actuators and generators. A 2.2-kW SyR motor prototype was tested to verify the feasibility of the proposed method. Key tuning aspects are addressed in this paper.
In this paper, a direct power control (DPC) technique is proposed for matrix converter-fed grid-connected doubly fed induction generators (DFIGs). In contrast to what has been investigated in the past for direct torque control (DTC) or DPC of matrix converter-fed DFIGs, the active and reactive powers are regulated in a fixed switching frequency using indirect space vector modulation (ISVM) technique. Hence, designing input filters for matrix converters (MCs) becomes convenient. In addition, the reactive component of input side of MC is controlled which leads to reduction of distortion in grid current waveform. Also, an extensive discussion is addressed for nonlinear voltage errors of MC that may cause inaccurate power control. Simulation results done in MATLAB/Simulink show the effectiveness of the proposed method.
This paper proposes a sensorless direct flux vector control scheme for synchronous reluctance motor drives. The proposed controller operates in stator flux oriented coordinates, regulating in closed-loop the amplitude of stator flux linkage and the current component quadrature to flux vector, at constant switching frequency. A hybrid position and speed observer is proposed, covering a wide speed range, based on backelectromotive force (EMF) integration and augmented at zero and low speed levels by high-frequency signal injection. Crosssaturation position estimation error is inherently compensated by the proposed observer scheme. Various experimental results for a 2.2-kW synchronous reluctance motor are presented to verify the feasibility of the proposed method.
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