Sensorless Direct Flux Vector Control of Synchronous Reluctance Motors Including Standstill, MTPA and Flux Weakening

This paper proposes a sensorless direct flux vector control scheme for synchronous reluctance motor drives. Torque is controlled at constant switching frequency, via the closed loop regulation of the stator flux linkage vector and of the current component in quadrature with it, using the stator flux oriented reference frame. A hybrid flux and position observer combines back-electromotive force integration with pulsating voltage injection around zero speed. Around zero speed, the position observer takes advantage of injected pulsating voltage. Instead of the commonly used current demodulation, the position error feedback is extracted here at the output of the observer’s flux maps, thus resulting in immunity towards the cross-saturation position error. The Maximum Torque per Ampere (MTPA) strategy is used. A detailed analysis puts in evidence the key advantages and disadvantages related to the use of the MTPA in the sensorless control of the Synchronous Reluctance machine, for both the saliency based and the back-EMF based sensorless methods. Extensive experimental results are reported for a 2.2 kW synchronous reluctance motor prototype, showing the feasibility of the proposed method. These include speed response to step and sinusoidal load disturbances at standstill, up to 121% of rated torque, and speed response tests covering the flux weakening speed region

An accurate self-commissioning technique for matrix converters applied to sensorless control of synchronous reluctance motor drives

The compensation of converters’ nonlinear voltage error is crucial in encoder-less control of ac motor drives. In this paper, a new self-commissioning and compensation method is proposed for matrix converters (MC). Similar to what done in the past for voltage source inverters, the MC voltage error is identified before the drive start and stored in a look-up table (LUT), later used for error compensation and accurate voltage estimate. Different from what observed in the past, the effect of parasitic capacitors on nonlinear voltage error of MCs in four-step current based commutation is observed and studied. Eventually, this method is applied to the sensorless control of a synchronous reluctance (SyR) motor drive, using the direct flux vector control (DFVC) concept. Experimental results are presented to validate the effectiveness of proposed self-commissioning in improving the performance of sensorless control at standstill and low speed

Direct Power Control of Matrix Converter-Fed DFIG with Fixed Switching Frequency

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.Peer reviewe

Self-commissioning algorithm for matrix converter, nonlinearity compensation

Matrix converter nonlinear errors due to voltage drop and commutation delay introduce a distortion between voltage reference signals and output phase voltages. In current controlled applications, the current regulators are capable of compensating for such voltage command error. However, where output voltage estimation is required such as in state observers used for sensorless control of ac drives, the converter error reduces the accuracy of the voltage estimate, especially at low speeds. This work proposes a simple and accurate technique for the identification of converter parameters before the drive startup. Based on the identified parameters, the nonlinearities are compensated. The feasibility and effectiveness of the presented method is shown in simulation. Experimental results are also reported