Unified Direct-Flux Vector Control for AC Motor Drives

The paper introduces a Unified Direct-Flux Vector Control scheme suitable for sinusoidal AC motor drives. The AC drives considered here are Induction Motor, Synchronous Reluctance and synchronous Permanent Magnet motor drives, including Interior and Surface-mounted Permanent Magnet types. The proposed controller operates in stator flux coordinates: the stator flux amplitude is directly controlled by the direct voltage component, while the torque is controlled by regulating the quadrature current component. The unified direct-flux control is particularly convenient when flux-weakening is required, since it easily guarantees maximum torque production under current and voltage limitations. The hardware for control is standard and the control firmware is the same for all the motors under test with the only exception of the magnetic model used for flux estimation at low speed. Experimental results on four different drives are provided, showing the validity of the proposed unified control approac

Sensorless Speed Control Scheme for Induction Motor Drive Using DC link Measurements

The controlled induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, the information on the rotor speed is extracted from measured stator voltages and currents at the motor terminals. Vector controlled drives requires estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open loop estimators or closed loop observers are used for this purpose. They differ with respect to accuracy, robustness and sensitivity against model parameter variations. This paper presents a new control strategy for three-phase induction motor which includes independent speed &torque control loops and the current regulation thereby overcoming the limitation (i.e. sluggish response) of volts per hertz controlled industrial drives. For closed-loop control, the feedback signals including the rotor speed, flux and torque are not measured directly but are estimated by means of an algorithm. The inputs to this algorithm are the reconstructed waveforms of stator currents and voltages obtained from the dc link and not measured directly on stator side. The proposed drive thus requires only one sensor in the dc link to implement the close-loop speed and torque control of a three-phase induction motor

Sensorless control for limp-home mode of EV applications

PhD ThesisOver the past decade research into electric vehicles’ (EVs) safety, reliability and availability has become a hot topic and has attracted a lot of attention in the literature. Inevitably these key areas require further study and improvement. One of the challenges EVs face is speed/position sensor failure due to vibration and harsh environments. Wires connecting the sensor to the motor controller have a high likelihood of breakage. Loss of signals from the speed/position sensor will bring the EV to halt mode. Speed sensor failure at a busy roundabout or on a high speed motorway can have serious consequences and put the lives of drivers and passengers in great danger. This thesis aims to tackle the aforementioned issues by proposing several novel sensorless schemes based on Model Reference Adaptive Systems (MRAS) suitable for limp-home mode of EV applications. The estimated speed from these schemes is used for the rotor flux position estimation. The estimated rotor flux position is employed for sensorless torque-controlled drive (TCD) based on indirect rotor field oriented control (IRFOC). The capabilities of the proposed schemes have been evaluated and compared to the conventional back-Electromotive Force MRAS (back-EMF MRAS) scheme using simulation environment and a test bench setup. The new schemes have also been tested on electric golf buggies. The results presented for the proposed schemes show that utilising these schemes provide a reliable and smooth sensorless operation during vehicle test-drive starting from standstill and over a wide range of speeds, including the field weakening region. Employing these new schemes for sensorless TCD in limp-home mode of EV applications increases safety, reliability and availability of EVs

Reduced--cost Permanent Magnet mottor drives: a comprehensive design procedure and a universall approach to the magnettiic modell identification and conttol

This research deals with the design, identification and control of Permanent Magnet Synchronous motor drives. Throughout the project, motor and control designs have been straightly integrated in order to meet the challenging requirements, typically coming from the industrial world. Namely, the purposes leading this research activity are: cost-reduction and standardization of both design and control tasks into straightforward and universal procedures. As a deeper insight, this work proposes a comprehensive procedure for the design of reduced-cost Permanent Magnet based electrical machines and a universal control technique, requiring minimum calibration and a simplified preliminary commissioning stage. The recent price volatility of rare earth raw materials has been compelling designers and manufacturers of electric motors to find out or re-evaluate alternative machine topologies, using either a reduced amount of such rare-earth magnets or lower energy density magnetic materials, such as hard ferrites, still providing for high-performance technologies. This thesis is about facing this issue, while enhancing general approaches to the optimal design of Permanent Magnet Synchronous machines via fully-analytical models showing a twofold purpos