Sensorless Commissioning and Control of High Anisotropy Synchronous Motor Drives

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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

Integrated Isolated OBC for EVs with 6-phase Traction Motor Drives

This work deals with a new topology of on-board integrated battery charger intended for road electric vehicles equipped with a 6-phase traction motor drive. The proposed OBC topology deeply integrates the battery charger within the e-drive powertrain, thus reducing cost and volume of the charger respect to non-integrated solutions. Moreover, galvanic insulation is provided, differently from all fully integrated charger in the literature. Finally, the charger has embedded PFC capability, so the AC grid current is absorbed at unitary power factor and low THD. Extensive simulation results show the feasibility of the proposed solution

Injectionless Sensorless Control of Synchronous Reluctance Machine for Zero to Low Speeds Region

An alternative to the high frequency injection approach for sensorless control at zero and low speed region is proposed for synchronous reluctance machines (SyR) using finite-control-set model predictive control (FCS-MPC). The saliency based position estimate aims to exploit the switching current ripple which is pronounced owing to the nature of MPC especially around zero and low speed region due to the minimal back-emf. A demerit of the high frequency injection techniques is the bandwidth hindrance of position observer by the demodulating low pass filter (LPF). In the proposed method, no such filters are required and consequently, high bandwidth is achieved. Guidelines for the calibration of observers are addressed. In addition, the effects of cross-saturation on position estimation is inherently considered. The experimental validation on a 1 kW SyR shows stable operation under torque and speed transients, and proves the feasibility of the proposed technique

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 Self-Commissioning of Synchronous Reluctance Machine with Rotor Self-Locking Mechanism

The paper proposes a sensorless technique for standstill self-commissioning of synchronous reluctance machines. Previous works have demonstrated the potential of simultaneous excitation of $d$ and $q$ axis with hysteresis square-wave voltage injection for the exploration of current plane with insignificant rotor movement. The proposed structure retains the hysteresis control for $q$ axis while $i_d$ is closed loop controlled using a weak PI regulator. Akin to the parking technique, a DC current is imposed in a fixed reference frame to inhibit any rotor movement and realize the self-locking mechanism. This permits systematic inspection of the $dq$ current plane for accurate cross-saturation modeling. In addition, a new approach for the identification of cross-saturation in $d$ axis from the high frequency component in $i_d$ current is developed. The experimental tests on 1.1 kW synchronous reluctance motor test bench prove the validity of proposed technique

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 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

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

Sensorless Magnetic Model and PM Flux Identification of Synchronous Drives at Standstill

This paper proposes a sensorless self-commissioning technique for PM-assisted synchronous reluctance motors. The identification of the machine’s flux maps is performed at standstill without any position transducer and with no need of rotor locking. The machine is first excited with alternated high voltage pulses, injected in the estimated d and q directions of the rotor to determine its saturation curves. Then, direct current values are applied in a fixed stator direction so that the rotor aligns in specific positions giving information on the PM flux linkage. Experimental results are provided on a PM-assisted synchronous reluctance motor prototype, confirming the validity of the proposed method. The key original feature of the proposed work is the estimation of magnet flux linkage at standstill. For the motor under test, the magnet flux linkage was sensorless estimated at standstill with an error lower than 3%