Adaptive Flux Observer Research Articles

Evaluation of Start-Up Performance of Induction Motor Speed Sensorless Vector Control Using Adaptive Flux Observer Considering Inverter Voltage Error

Speed sensorless vector control for induction motors using an adaptive flux observer makes it difficult to output high and stable torque at a standstill condition when the output voltage error mainly due to dead-time of the inverter. This voltage error leads to a speed estimation error. Consequently, axis misalignment occurs, and a torque value that tracks the reference command value cannot be output. A method has been proposed to compensate for this voltage error by using a current command value; however, the compensation accuracy is limited because of the forward voltage drop and nonlinear characteristics of power switching devices. This study applies the conventional dead-time compensation to the model reference adaptive system, and the effect of varying the amount of compensation, instead of investigating the true dead-time length, on the start-up is evaluated using a 2.2 kW experimental system and through dynamic analysis.

Sensorless Adaptive Observers for Linearly Parameterized Class of Induction Machine

In this paper a new adaptive flux, speed, load torque and rotor resistance observer is proposed for induction machine drive system. The structure of the proposed observer is simple and it is able to give rise to different observers among which adaptive high gain and adaptive sliding mode. We adopt a mild change of coordinates that allows to easily design of adaptive observer. Computer simulation results verify the validity of the proposed estimation algorithm.

Enhanced Direct Torque Control of a Syn-RM, Using Adaptive Flux Observer, Including Magnetic Saturation and Iron Losses

Enhanced Direct Torque Control of a Syn-RM, Using Adaptive Flux Observer, Including Magnetic Saturation and Iron Losses

Virtual voltage vector based predictive current control of speed sensorless induction motor drives

Nowadays, predictive current control (PCC) strategy has been recognized as a promising option for the control of electric drives for their control flexibility, fast dynamic response and weighting factorless structure of objective function. However, such kinds of conventional control strategies make drives to suffer from the ingress of significant harmonics in stator current, increasing further the steady state flux ripple followed by a noticeable torque ripple. To ameliorate these aforementioned shortcomings of conventional scheme, the present work employs the concept of virtual voltage vector (V3) in PCC strategy. The mathematical steps of the proposed V3PCC make the scheme more frontward in delay compensation, and also less parameter sensitive than the conventional one. As a baseline for the performance analysis, the present V3PCC is compared with a weighting factorless V3 based predictive flux control (PFC) scheme in induction motor (IM) drive. A speed adaptive flux observer is considered for the speed estimation purpose in both the control schemes. The performance of both the sensorless schemes for IM drive are analysed in MATLAB/Simulink, and also experimentally verified in a 2.2 kW IM drive test bench.

Optimization of Observer Feedback Gains for Stable Sensorless IM Drives at Very Low Frequencies: A Comparative Study between GA and PSO

Instability of an adaptive flux observer (AFO) in the regenerating mode at low frequencies is a great challenge of sensorless induction motor (SIM) drives. Zero observer feedback gains (OFGs) in the regenerating mode at low frequencies are the main reasons for moving the dominant zero of the speed estimators to the unstable region. OFGs should be appropriately selected to transfer the unstable dominant zero to the stable region. In this paper, genetic algorithm (GA) and particle swarm optimization (PSO) techniques were used to design the OFGs for a stable observer. A fair comparison of the dominant zero location between the two approaches using the optimized OFGs is presented under parameter deviation. Analytical results and the design procedure of the OFGs using the two approaches are presented under deviations of stator resistance and mutual inductance to guarantee a stable dominant zero in the regenerating mode of IM. The dominant zeros obtained by PSO had a superior location to that obtained by GA for both stator resistance and mutual inductance deviations. It was observed that one of the gains had an almost constant value over a wide range of parameter deviations. However, the value of the other gain was dependent on the deviation of machine parameters. The advantage of using PSO over GA is that the relation between the gain and parameter deviation can be represented by a deterministic and mostly linear relationship. Simulation and experimental work of the SIM drive are presented and evaluated under the optimized OFGs.

Predictive Torque Control Strategy for Speed Adaptive Flux Observer Based Sensorless Induction Motor Drive in Flux-Weakening Region

In general, flux-weakening operation of induction motor (IM) drive to achieve control above the rated speed is challenging. The challenge further aggravates if the drive becomes speed sensorless. This article primarily focuses on the flux-weakening operation of adaptive flux observer-based speed sensorless IM drive working under a promising predictive torque control (PTC) regime. The flux-weakening operation, in this case, is more challenging because of the involvement of additional unavoidable estimation strategies essential for PTC algorithm, thereby further deteriorating drive's performance in the flux-weakening region if not addressed suitably. In this article, a simple flux and torque scaling factor-based approach is introduced in the PTC algorithm of the adopted sensorless IM drive to improve the performance in flux-weakening region. The drive's performance in terms of speed tracking is thoroughly investigated in MATLAB/Simulink. Moreover, stability study in the entire operating range has also been done in the same environment. Experimental results demonstrating the speed of operation up to 3.5 times the base speed as obtained with 2.2 kW IM drive interfaced with dSPACE ds1103 controller are also presented in this article.

Five phase permanent magnet synchronous motor decoupled model with dual frame frequency adaptive flux observer

In this paper, a five-phase permanent magnet synchronous motor (five phase PMSM) decoupled model is proposed to avoid the inaccuracy and computational complexity of conventional five phase PMSM model, which always ignores the mutual inductance between the fundamental and harmonic flux linkage. Unlike traditional inductances based five phase PMSM model, the proposed five phase PMSM decoupled model is built based on flux linkages. Moreover, to improve the accuracy of the proposed five phase PMSM decoupled model for model predictive control, a duel frame-frequency adaptive flux observer (DF-FAFO) is proposed, which can estimate both fundamental flux linkage and 3rd harmonic flux linkage online. The DF-FAFO can estimate the flux linkages accurately and minimize the unwanted harmonic ripple even if the torque is changed. The effectiveness of the proposed decoupled model and the DF-FAFO is demonstrated by simulations.

SPEED OBSERVER FOR SENSORLESS ENERGY GENERATION SYSTEMS BASED ON FIELD ORIENTED INDUCTION GENERATOR

The paper presents a novel adaptive speed – rotor flux linkage observer for sensorless field oriented control of induction generators. The proposed solution is based on Matsuse observer structure to- gether with specially designed correction terms and utilize current measurement and calculated stator volt- ages for real-time flux and speed reconstruction. A special coordinate transformation is used to avoid non- linear parametrization in the right side of flux linkages differential equations. Adaptive observer is designed in two steps: at the first step nonadaptive flux linkage observer is designed under condition of speed meas- urement; at the second step adaptive to rotor speed version of the flux linkage observer is designed. Infor- mation about rotor speed for adaptive flux observer is calculated by developed speed observer. A second Lyapunov’s method together with adaptive control theory are utilized for observer’s correction terms synthe- sis and stability proof. Designed adaptive observer under persistence of excitation conditions guarantees local exponential estimation of constant rotor speed and flux linkage vector components of induction ma- chine. From the practical point of view persistency excitation conditions are met if rotor flux linkages are nonzero. Proposed solution investigated by simulations. It is shown, that developed adaptive speed observer provides asymptotic estimation of induction motor currents, speed and flux linkage components under con- stant speed conditions. For varying speed proposed observer provides estimation of required variables with a small dynamic error. Proposed observer can be used in energy generation systems based on induction generators as well as in sensorless induction motor-based drive systems with constant or slowly varying ro- tor speed.

Speed Sensor-Less Predictive Torque Control for Five-Phase Induction Motor Drive Using Synthetic Voltage Vectors

The predictive torque control (PTC) is researched extensively for control of electrical drives because of its fast-dynamic response and robust control. In multiphase motors, it is mandatory to design a multiobjective cost function with more than two terms for controlling xy-subspace current and common-mode voltage (CMV). However, selecting the weighting factor for multiple control variables is time penalizing and increases the computational burden. Using a noisy speed input from the speed sensor in the prediction model reduces the steady-state performance in terms of higher torque ripple, flux ripple, and phase current total harmonic distortion (THD), especially during low speeds. In this article, PTC for a five-phase induction motor (IM) drive without speed sensor [sensorless PTC (PTC-S)] is presented. The adaptive full observer is incorporated to estimate the stator flux, stator resistance, and rotor speed. The proposed algorithm is capable to eliminate CMV and xy-current harmonics having advantages over the conventional PTC (PTC-C) algorithm. The elimination of CMV is achieved by the selection of set of voltage vectors from available 243 voltage vectors. The proposed speed sensor-less control is implemented with a three-level neutral-point clamped (NPC) inverter using synthetic voltage vectors. The use of a synthetic voltage vector eliminates the xy-subspace current and reduces the computational burden. The PTC-S is implemented with a seven-level hysteresis torque comparator, which reduces the torque ripple significantly. To further improve the effectiveness of the control algorithm, two-step delay compensation is implemented. The discussed algorithms are tested on a laboratory prototype for experimental evaluation. The proposed study also highlights the effect of torque ripple reduction on the speed adaptive flux observer for sensor-less operation. The experimental results show the effectiveness and applicability by comparing the steady-state and dynamic performances of PTC.

Design of an Adaptive Flux Observer for Sensorless Switched Reluctance Motors Using Lyapunov Theory

This paper proposes an adaptive flux observer for a sensorless switched reluctance motor. The observer adaptive gains are designed using the Lyapunov theory to guarantee both the accur ...

Performance and Stability Improvement of AFO for Sensorless IM Drives in Low Speeds Regenerating Mode

This paper proposes an adaptive flux observer (AFO) method of sensorless induction motor (IM) drives. The AFO gains are designed to ensure accurate estimated speed, especially at very low frequencies in the regenerating mode of operation. Stability analysis of AFO with the designed gains is presented using the Lyapunov theory. These gains are calculated to be adaptively dependent on the IM variables and parameters. The observer gains play a significant role on the stability and precision of AFO in the regenerating mode. The influence of the machine parameters mismatch on the AFO stability with zero feedback gains as well as the proposed feedback gains is provided. The sensitivity to stator resistance is also analyzed. The complete sensorless IM drive with the proposed AFO is executed by both MATLAB/Simulink program, and also in the laboratory. Analytical and experimental results under various working conditions are provided to prove the effectiveness of the proposed AFO, especially at very low stator frequencies.

Analysis of Magnetic Properties of AlNiCo and Magnetization State Estimation in Variable-Flux PMSMs

Variable-flux permanent-magnet synchronous machines have gained a lot of attention for their ability to expand the speed range and reduce loss over an electric vehicle drive circle by manipulating magnetization state (MS) dynamically. In this paper, a combined-magnet-pole variable-flux machine (CMP-VFM) using both AlNiCo and NdFeB is analyzed. To obtain the variation laws of MS quickly and precisely, a 3-D neural-network hysteresis model of AlNiCo is proposed, and the accuracy and time consumption of the proposed neural-network hysteresis model are evaluated. In order to optimally utilize the speed expansion and loss minimization capability with precise MS control, a flux observer based on model reference adaptive theory is proposed for the closed-loop flux control of CMP-VFM and validated by simulations. The simulation results prove that the accuracy of the proposed adaptive flux observer is almost not affected by parameter disturbance.

Adaptive Flux Observer for Nonsalient PMSM with Noised Measurements of the Current and Voltage

An algorithm of adaptive estimation of the magnetic flux for the non-salient permanent magnet synchronous motor (PMSM) for the case when measurable electrical signals are corrupted by a constant offset is presented. A new nonlinear parameterization of the electric drive model based on dynamical regressor extension and mixing (DREM) procedure is proposed. Due to this parameterization the problem of flux estimation is translated to the auxiliary task of identification of unknown constant parameters related to measurement errors. It is proved that the flux observer provides global exponential convergence of estimation errors to zero if the corresponding regression function satisfies the persistent excitation condition. Also, the observer provides global asymptotic convergence if the regression function is square integrable. In comparison with known analogues this paper gives a constructive way of the flux reconstruction for a nonsalient PMSM with guaranteed performance (monotonicity, convergence rate regulation) and, from other hand, a straightforwardly easy implementation of the proposed observer to embedded systems.

Sensorless high-order sliding modes vector control for induction motor drive with a new adaptive speed observer using super-twisting strategy

This paper proposes a high-order super-twisting sliding mode control method applied to an induction motor fed by a power voltage source without speed sensor. Based on the vector control principle, high-order super-twisting sliding mode controllers in speed loop and flux loop are designed respectively. The super-twisting sliding mode control is utilised to improve the response speed and robustness of motor control systems. Meanwhile, high-order sliding modes are adopted to eliminate the chattering phenomenon. We also present the mechanism of adaptive super-twisting speed and rotor flux observers with the only assumption that from stator voltages and currents are measurable. The objective is to improve the speed control, the rotor flux control under load torque disturbances and parameter variations. The simulation results prove clearly a good robustness against load torque disturbances, the estimated fluxes and the rotor speed converge to their real values. Our study is close to reality; all the simulations are based on real models simulated within the Matlab SymPower System environment in continuous time.

Design and implementation of a speed adaptive flux observer for the induction motor using Sylvester criterion

The paper presents the design and implementation of a flux and speed observer for the induction motor drive. The method employs an observer with linear feedback that yields the motor fluxes and also estimates the speed using an adaptive law. The convergence conditions are formulated based on Lyapunov's nonlinear stability theory. The gains of the observer are designed using Sylvester criterion. The method proposed is reasonably simple and yields a series of inequalities that provide insight into the design choices and stability margins of the observer. The paper shows that the observer is not globally stable - however, with proper design of the adaptation gains, it can be made locally stable. The observer with the corresponding adaptive speed estimate does not perform during low speed regeneration - the speed estimate diverges; to solve this issue, the paper shows a modified adaptation law that yields a stable speed estimate.

Design and implementation of a speed adaptive flux observer for the induction motor using Sylvester criterion

The paper presents the design and implementation of a flux and speed observer for the induction motor drive. The method employs an observer with linear feedback that yields the motor fluxes and also estimates the speed using an adaptive law. The convergence conditions are formulated based on Lyapunov's nonlinear stability theory. The gains of the observer are designed using Sylvester criterion. The method proposed is reasonably simple and yields a series of inequalities that provide insight into the design choices and stability margins of the observer. The paper shows that the observer is not globally stable - however, with proper design of the adaptation gains, it can be made locally stable. The observer with the corresponding adaptive speed estimate does not perform during low speed regeneration - the speed estimate diverges; to solve this issue, the paper shows a modified adaptation law that yields a stable speed estimate.

Speed-Sensorless DTC of a Matrix Converter Fed Induction Motor Using an Adaptive Flux Observer

ABSTRACT This paper aims at combining some of the best features of an available induction motor (IM) drive system while introducing a simplified adaptive flux estimation algorithm for sensorless operation. The use of a matrix converter (MC) is proposed to achieve improved source side power quality and input power factor correction of an IM drive. Direct torque control (DTC) of an IM is realized through appropriate switching of the MC and the control strategy is implemented with speed-sensorless operation by using a relatively simplified adaptive flux observer. DTC through speed and flux estimation is realized in the stationary reference frame. Primarily, three objectives are achieved, viz. speed regulation while directly controlling the motor torque (and flux), improved source side power quality owing to the use of MC, and substantially simplified sensorless estimation strategy. Additionally, economic benefits are also achieved owing to negligible energy storage requirements of the drive and sensorless operation.

A robust adaptive flux observer for a class of electromechanical systems

ABSTRACT The problem of designing a flux observer for magnetic field electromechanical systems from noise corrupted measurements of currents and voltages is addressed in this paper. Imposing a constraint on the systems magnetic energy function, which allows us to construct an algebraic relation between fluxes and measured voltages and currents that is independent of the mechanical coordinates, we identify a class of systems for which a globally convergent adaptive observer can be designed. A new adaptive observer design technique that effectively exploits the aforementioned algebraic relation is proposed and successfully applied to the practically important examples of permanent magnet synchronous motors and magnetic levitation systems.

Sensorless Induction Motor Drives Using Adaptive Flux Observer at Low Frequencies

Operation at low frequencies of sensorless drives using machine model-based estimation methods is a challenging issue. This paper proposes an adaptive flux observer (AFO) method of speed estimation for sensorless induction motor drives. The observer feedback gains are designed to guarantee accurate speed estimation, especially at low frequencies in the regenerating mode operation. A complete sensorless IM drive with the proposed AFO is executed in the laboratory. Extensive experimental results under different operating conditions are provided to prove the effectiveness of the proposed AFO, particularly under low stator frequencies in both motoring and regenerating modes of operation.

Combined Speed and Direct Thrust Force Control of Linear Permanent-Magnet Synchronous Motors With Sensorless Speed Estimation Using a Sliding-Mode Control With Integral Action

A sliding-mode-based control scheme with integral action for combined speed and direct thrust force control of a linear permanent-magnet synchronous motor is proposed. A nonlinear state-space model for the combined dynamics of speed and thrust force as system states is utilized for the synthesis of the sliding-mode control law. Direct integral action is also included in the control law to eliminate the steady-state error in the speed tracking. The sensorless speed estimation is performed by using an adaptive flux observer with a modified dual boundary layer sliding-mode component. Lyapunov stability analysis to prove the global asymptotic stabilities of both the controller and observer is provided. The effectiveness of the proposed method is validated experimentally and demonstrates excellent transient and steady-state speed control performance.