727 research outputs found
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
Sensorless Control of Synchronous Reluctance Motor Drives: Improved Modeling and Analysis Beyond Active Flux
The paper presents a framework for the design and analysis of position observers for sensorless control of synchronous reluctance machines. An improved inductance model is developed to account for the position error induced inductance variations. The instability regions of active flux based position observer are analytically identified and validated. A novel technique, Adaptive Projection vector for Position error estimation (APP), that alleviates the stability problems is introduced. Furthermore, the proposed technique can be augmented with a second projection vector to estimate speed error independently of the position error, referred to as Adaptive Projection vector matrix for Position and Speed error estimation (APPS). Stability and performance of proposed technique is validated on a 1 kW synchronous reluctance motor test bench
Position-sensorless control of permanent-magnet-assisted synchronous reluctance motor
The sensorless control of permanent-magnet-assisted synchronous reluctance (PMASR) motors is investigated, in order to conjugate the advantages of the sensorless control with full exploitation of the allowed operating area, for a given inverter. An additional pulsating flux is injected in the d-axis direction at low and zero speed, while it is dropped out, at large speed, to save voltage and additional loss. A flux-observer-based control scheme is used, which includes an accurate knowledge of the motor magnetic behavior. This leads, in general, to good robustness against load variations, by counteracting the magnetic cross saturation effect. Moreover, it allows an easy and effective correspondence between the wanted torque and flux and the set values of the chosen control variables, that is d-axis flux and q-axis current. Experimental verification of the proposed method is given, both steady-state and dynamic performance are outlined. A prototype PMASR motor will be used to this aim, as part of a purposely assembled prototype drive, for light traction application (electric scooter
Cross-Saturation Effects in IPM Motors and Related Impact on Sensorless Control
Permanent-magnet-assisted synchronous reluctance motors are well suited to zero-speed sensorless control because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in this paper as a function of the working point. The errors that are calculated are then found to be in good accordance with the purposely obtained experimental measurement
Impact of cross-saturation in sensorless control of transverse-laminated synchronous reluctance motors
Synchronous reluctance (SyR) motors are well suited to a zero-speed sensorless control, because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in the paper, as a function of the working point. The so-calculated errors are then found in good accordance with the purposely obtained experimental measurements. The impact of the amplitude of the carrier voltage is then pointed out, leading to a mixed (carrier injection plus electromotive force estimation) control scheme. Last, a scheme of this type is used, with a commercial transverse-laminated SyR motor. The robustness against cross-saturation is shown, in practice, and the obtained drive performance is pointed out proving to be effective for a general-purpose applicatio
Local weak observability conditions of sensorless AC drives
Alternating current (AC) electrical drive control without mechanical sensors
is an active research topic. This paper studies the observability of both
induction machine and synchronous machine sensorless drives. Observer-based
sensorless techniques are known for their deteriorated performance in some
operating conditions. An observability analysis of the machines helps
understanding (and improving) the observer's behavior in the aforementioned
conditions.Comment: arXiv admin note: text overlap with arXiv:1512.0366
Observability analysis of sensorless synchronous machine drives
This paper studies the local observability of synchronous machines using a
unified approach. Recently, motion sensorless control of electrical drives has
gained high interest. The main challenge for such a technology is the poor
performance in some operation conditions. One interesting theory that helps
understanding the origin of this problem is the observability analysis of
nonlinear systems. In this paper, the observability of the wound-rotor
synchronous machine is studied. The results are extended to other synchronous
machines, adopting a unified analysis. Furthermore, a high-frequency
injection-based technique is proposed to enhance the sensorless operation of
the wound-rotor synchronous machine at standstill
Permanent Magnet minimization in PM-Assisted Synchronous Reluctance motors for wide speed range
This paper presents a technique to modify the rotor lamination of a permanent-magnet-assisted synchronous reluctance motor, in order to reduce the magnet volume with no side effect on performance. A closed-form analysis, which is based on a lumped parameter model, points out that the magnet quantity can be minimized with a significant saving of material volume and cost. At a second stage, the risk of demagnetization is evaluated since the minimized magnets are thinner than the starting ones and work on lower load lines in their respective B-H planes. A feasible drawing is analytically defined, which is robust against demagnetization at overload, showing that the saving of magnet quantity depends on the maximum current overload and can be significant. The theoretical formulation is validated with finite-element analysis and experiments on a prototype machin
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