Novel Sensorless Control Algorithm for SyR Machines Based on Low Speed Active Flux

This work deals with encoderless control of synchronous reluctance machines at low and zero speed. The algorithm is based on active flux method, often exploited to retrieve the rotor position at sufficiently high speed. being a model based technique, the active flux commonly fails when the speed is too low due to lack of back-emf and so low signal-to-noise ratio, and is impossible at standstill. The active flux concept is now generalized and extended to cover also the low speed range, where the control is enhanced by HF voltage injection. The fundamental and HF machine models are decoupled, permitting to exploit the model based algorithm also at standstill. The proposed technique was experimentally tested in a 1.1 kW motor prototype with promising results

Sensorless Commissioning and Control of High Anisotropy Synchronous Motor Drives

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Sensorless Commissioning of Synchronous Reluctance Machines Augmented with High Frequency Voltage Injection

This paper deals with the self-commissioning of synchronous reluctance motors. Previous work has demonstrated that the motor flux maps can be accurately identified at standstill by exciting the machine with square-wave voltage pulses of large amplitude, of the same order of the machine nominal voltage. This was made without the need of rotor locking and without using position sensors. The knowledge of the d and q axes position was obtained by a preliminary sensorless commissioning and then used for directing the d and q voltage pulses accordingly, in open-loop fashion. At free shaft, the position tends to oscillate under such alternated excitation, introducing position error and thus inaccuracy. For high values of the torque current component the rotor can even start spinning suddenly, thus stopping the identification. The loss of control impedes of identification of the flux maps above a certain limit, at least in the q direction. In the past, polynomial fitting was used to extrapolate the flux map in the missing parts of the dq current domain, with good results. In this paper, the rotor position is closed-loop estimated during the motor commissioning, so to counteract the occurrence of sudden spin and extend the explored current area in the q direction. An additional pulsating voltage, also of the square-wave type, is superimposed to the main excitation voltage, and the position is tracked through current demodulation. In this way, the area explored in the dq current plane is substantially extended, if compared to previous method. The proposed approach is verified through experimental results on one synchronous reluctance motor prototype

Standstill Determination of PM Flux Linkage Based on Minimum Saliency Tracking for PM-SyR Machines

Permanent Magnet assisted Synchronous Reluctance (PM-SyR) motors often present relevant magnetic saturation, especially if overload capabilities want to be exploited. The knowledge of current-to-flux relationship is mandatory for proper motor control, and it becomes even more critical in case of sensorless applications. Reliable self-commissioning tests have been recently developed for Synchronous Reluctance (SyR) motors without producing any rotor movements. This procedure can be extended to PM-SyR motors, but, being at standstill, it does not retrieve the flux contribution related to the PMs. This paper integrates the identification of the flux characteristic including a novel test for estimating the PM flux, obtaining the complete magnetic characteristic of PM-SyR motors. The global identification session is performed at standstill and without a position transducer, while the load can either be connected or not. These conditions are considered the most demanding for selfcommissioning tests. The machine is first excited with a proper sequence of bipolar high voltage pulses to determine its current dependent flux component. Then, the PM flux linkage is retrieved at standstill by evaluating the local saliency along the negative q axis. The proposed method was experimentally verified on a 10 kW PM-SyR motor prototype, with an estimation error of 0.42%

Sensorless standstill commissioning of synchronous reluctance machines with automatic tuning

This paper deals with the sensorless selfcommissioning of synchronous reluctance motors at standstill. Previous work demonstrated that the injection of high test voltage pulses can be successfully used to determine the flux linkage maps of the Synchronous Reluctance machine without position transducer and with no need of rotor locking. In this work, the tuning aspects of the above self-commissioning technique are analyzed for making it self-tuning. A method for detecting unwanted rotor movement during the test is introduced and used to assess the test’s end and to maximize the id, iq area of inspection. Furthermore, the paper analyzes a number of theoretical and practical implementation issues, first mathematically and then in experiments. The effects of possible error sources are evaluated, including imprecise estimation of the stator resistance and of the inverter voltage distortion, and iron loss. Experimental results are presented for three Synchronous Reluctance motor prototypes

Automatic Tuning for Sensorless Commissioning of Synchronous Reluctance Machines Augmented with High Frequency Voltage Injection

Sensorless control of synchronous reluctance motors relies on the knowledge of the machine current-to-flux maps. Previous work demonstrated the feasibility of sensorless identification of the flux maps, performed by exciting the machine with square-wave voltage pulses at standstill, and without the need of rotor locking. The rotor position was initially estimated and then used throughout the identification, in open-loop fashion. In some cases, rotor oscillation and eventually position drift led to stop the identification before the programmed dq current domain was covered entirely. In this paper, the rotor position is closed-loop tracked during the motor commissioning to counteract the occurrence of rotor movement. The hysteresis-controlled excitation voltage is augmented with a high-frequency square-wave voltage component, and the position is tracked through demodulation of the current response to such high-frequency component. The proposed approach is experimentally verified on a 2.2 kW synchronous reluctance motor prototype. The results show that the id, iq commissioning domain is substantially extended, resulting in more accurate flux maps. Moreover, self-tuning of the method is addressed and possible causes of error are analyzed and commented

Determination of PM Flux Linkage Based on Minimum Saliency Tracking for PM-SyR Machines without Rotor Movement

Permanent magnet assisted synchronous reluctance (PM-SyR) motors often present relevant magnetic saturation, especially if overload capability is exploited. The knowledge of current-to-flux relationship is mandatory for proper motor control, and it becomes even more critical in the case of sensorless applications. Reliable standstill self-commissioning tests have been recently developed for synchronous reluctance (SyR) motors without producing rotor movement. This procedure can be extended to PM-SyR motors, but being at standstill, it does not retrieve the flux contribution related to the permanent magnets (PMs). This article integrates the identification of the flux characteristics including a novel test for estimating the PM flux linkage, obtaining the complete magnetic characteristic of the PM-SyR motor. The identification session is performed at standstill and without a position transducer, independently of the mechanical load being connected or not. Such conditions are considered the most demanding for self-commissioning tests. The machine is first excited with a proper sequence of bipolar high voltage pulses to determine its current-dependent flux components. Then, the estimate of PM flux linkage is retrieved at standstill by evaluating the local saliency along the negative q-axis. The proposed method is supported by detailed finite element analysis and experimentally verified on two PM-SyR motor prototypes, confirming the accuracy of the PM flux linkage estimate

Self-Commissioning of Synchronous Reluctance Motor Drives: Magnetic Model Identification with Online Adaptation

3siA new magnetic model self-identification technique is proposed to build the flux-map look-up tables (LUTs) for synchronous reluctance (SyR) machines. Provided the shaft is free to turn, an alternating acceleration and deceleration sequence is envisaged for identification without a dedicated experimental rig or additional hardware. Respect to previous works, the stator flux and the stator resistance are adapted online during the run, thus eliminating the need for post-processing and the sensitivity to winding temperature variations during the test. Experimental validation on a 1.1 kW SyR motor test-bench shows promising results.partially_openopenVaratharajan, Anantaram; Pellegrino, Gianmario; Armando, EricVaratharajan, Anantaram; Pellegrino, Gianmario; Armando, Eri

Kinetic-Rotor Self-Commissioning of Synchronous Machines for Magnetic Model Identification with Online Adaptation

This paper proposes a new magnetic model self-identification technique for synchronous machines to build the flux-map look-up tables (LUTs). Provided the shaft is free to turn, an alternating self-acceleration and deceleration sequence is envisaged for identification without a dedicated experimental rig or additional hardware. Respect to previous works, the stator flux and the stator resistance are adapted online during the run, thus eliminating the need for post-processing and the sensitivity to winding temperature variations during the test. Experimental validations on a 1.1 kW synchronous reluctance (SyR) and a 11 kW permanent-magnet assisted synchronous reluctance (PM-SyR) motors are provided

Analysis and Exploitation of the Star-Point Voltage of Synchronous Machines for Sensorless Operation

In the field of sensorless drive of synchronous machines (SMs), many techniques have been proposed that can be applied successfully in most applications. Nevertheless, these techniques rely on the measurement of the phase currents to extract the rotor position information. In the particular case of low-power machines, the application of such techniques is challenging due to the limited bandwidth of the available current sensors. An alternative is offered by those techniques that exploit the star-point voltage rather than phase currents. This work aims at providing a model of the dynamic behavior of the star-point voltage and presenting a technique for extracting the rotor electrical position needed for sensorless operation of SMs. Two different circuitries for measuring the star-point voltage are also presented and then compared. The presented mathematical analysis and the measurement methods are validated both numerically and experimentally on a test machine