Rotor Time Constant Variation Research Articles

Correction of Field Orientation Inaccuracy Caused by Resolver Periodic Error and Rotor Time Constant Variation for Indirect Field-Oriented Control Induction Motor Drives

This article proposes an algorithm correcting the field orientation inaccuracy caused by resolver periodic error and rotor time constant variation. It is found that the periodic error brings harmonic current vectors and torque ripples while the rotor time constant variation makes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> currents deviate from the reference values. The cross-product of fundamental and harmonic current vectors contains the information of resolver periodic error. The gradient descent method with a variable step is introduced to compensate the periodic error. During the process, the cross-product is minimized. A new form of cross-product calculation is derived to reduce the computation time. The rotor time constant is identified by the reactive-power based model reference adaptive system (MRAS). Voltages and currents in the stationary reference frame are used in the reference model to avoid the influence of resolver periodic error. Appropriate parameters of the MRAS are selected to guarantee the stability. The algorithm is integrated with an induction motor drive which is based on indirect field-oriented control. The feasibility of the proposed algorithm is verified by simulation results and experiments.

Fuzzy Improvement on Luenberger Observer Based Induction Motor Parameters Estimation for High Performances Sensorless Drive

In this paper we present a new improved sensorless vector control of induction motor based on an improved adaptive Luenberger observer. The proposed observer is designed to estimate both speed and motor parameters from measured stator currents, stator voltages and estimated rotor fluxes. The proposed sensorless drive has for purpose to compensate at the same time both stator resistance and rotor time constant inverse variation, which change during operation. Indeed, in the proposed adaptive Luenberger observer, a Fuzzy Logic Controller will be adopted as an adaptation mechanism. The proposed observer stability is proved by the Lyapunov’s theorem and its feasibility is verified by series of experimental tests. The relevant results and the effectiveness of the improved system are clearly shown through obtained experimental results with an induction motor of 1 kW driven by dSPACE system.

Offline method for experimental identification of load‐dependentsaturation of induction motor taking into account variation of inverse rotortime constant

Accurate knowledge of induction machine parameters has a direct impact on the overall performance of field-oriented control strategies. In the case of rotor flux oriented control, parameter mismatch causes a discrepancy in the estimated rotor flux position and amplitude. Magnetising inductance is one of the parameters whose detuning has a direct impact on the setpoints of the control loops and estimation of hardly or non-measurable quantities. Conventional iron saturation, which can be obtained by a standard no-load test, is not the only type of saturation occurring in the machine. Depending on the rotor design, the magnetising inductance and the rotor leakage inductance may also strongly saturate as a function of load and, thus, rotor current. Based on the authors’ previous work, a new, improved experimental method for identifying the load-dependent saturation of induction motor, which takes into account variation of the inverse rotor time constant, is proposed. Experimental results conducted on 12 kW motor show improved static and dynamic behaviour of the drive compared to the constant parameter model.

Rotor Resistance Estimation of Vector Controlled Induction Motor Drive using GA/PSO t uned Fuzzy Controller

Induction motor with indirect field oriented control is preferred for high performance applications due to its excellent dynamic behavior. However, it is sensitive to variations in rotor time constant, especially variation in rotor resistance which needs to be estimated online. Conventionally the model reference adaptive system with fuzzy logic controllers as adaptation is used, which works satisfactorily for one particular operating condition and fails under variable operating condition. Therefore the need arises for a fuzzy controller whose parameters are tuned using evolutionary algorithm. In this paper, the input/output gain and the membership function parameters of the fuzzy system are optimized using genetic algorithm and particle swarm optimization to obtain an optimal designed fuzzy controller for rotor resistance estimation. The system is investigated in MATLAB/Simulink environment. Results shows that the steady state error in estimation of rotor resistance by the proposed controller under stringent operating condition is better with the proposed controller as compared to the conventional trial and error based fuzzy controller. Index Terms: Induction motor (IM), Indirect Rotor flux Field Oriented Vector Control (IRFOC), Rotor Flux Model Reference Adaptive system (RF-MRAS), Proportional Integral (PI) controller, Mamdani fuzzy controller, Genetic Algorithm (GA), Particle Swarm Optimization (PSO).

A Novel Rotor Resistance Estimation Technique for Vector Controlled Induction Motor Drive Using TS Fuzzy

Induction motor with indirect field oriented control is well suited for high performance applications due to its excellent dynamic behavior. But, the indirect field oriented controller is sensitive to variations in rotor time constant, especially variation in rotor resistance. In this study a scheme based on the Rotor flux Model Reference Adaptive Controller is used for on line identification of the rotor resistance and thus improving the steady state performance of the drive. The overriding feature of this estimation technique is the accurate identification of rotor resistance especially during transient and steady state conditions when the drive is operating at full load and at zero motor speed condition. Moroever, the effectiveness of the TS fuzzy controller utilizing rotor flux for online estimation of rotor resistance for four quadrant operation of motor drive is investigated and compared with the conventional PI and Mamdani fuzzy controller Simulation results in MATLAB/Simulink environment.have been presented to confirm the effectiviness of the technique.

Robust Control Method of Induction Machine against Temperature Variation

This paper proposes a control method robust against the rotor temperature variation for the induction machine used in the xEV traction application. The rotor resistance (or time constant) of the induction machine varies with the rotor temperature so that its torque control performance will be degraded if this variation is not properly compensated. In this paper, firstly a direct vector control method, which is based on the rotor flux estimator using the current model in the synchronous reference frame, is adopted in order to control the DQ-axis rotor fluxes independently. Secondly, the rotor time constant variation is compensated utilizing the flux estimation difference between the voltage and current models. This method has no transition region which is inevitable in the conventional method that uses the current model in the low speed region and the voltage model in the high speed range for estimating the rotor flux. The robustness to the temperature change of the proposed method is validated through the experiment in the motoring and regeneration modes.

A Novel Identification Method of Rotor Time Constant of Induction Motor

Vector control system is dependent of parameters of motor, and rotor time constant usually changes with temperature. Through analyzing the influence of rotor time constant variations on the control system performance, a novel identification method based on adaptive flux observer is presented. Different with traditional pole assignment method, it implies robust control theory and Lyapunov stability theory, by solving a linear matrix inequality (LMI) to obtain the feedback gain matrix. The simulation results show that this method can identify the rotor time constant of induction motor accurately, and it has rapid converge, good indiscrimination degree and strong robustness.

NEW CONTROL STRATEGY FOR SENSORLESS VECTOR CONTROL IM DRIVES WITH ROTOR TIME CONSTANT ESTIMATION

A sensorless induction motor vector control scheme is proposed taking into account the compensation of the inverse rotor time constant variation. The model reference adaptive system (MRAS) method based on back EMF is considered for concurrent estimate of the speed and inverse rotor time constant. Two observers are used simultaneously; the deterministic MRAS observer that estimates the speed and inverse rotor time constant, and a Kalman Filter observer for rotor flux estimation. The induction motor speed control is made possible by combining the hybrid MRAS and Kalman Filter structure. Theoretical background including the stability is confirmed by the numerical simulations, and the results seem to be satisfactory for a large speed bandwidth and torque load.

A Fuzzy Method for Rotor Time Constant Estimation for High-Performance Induction Motor Vector Control

This paper describes an on-line rotor time constant estimation in a field-oriented control of an induction motor. The detuning of the indirect field-oriented induction motor drive due to rotor time constant variation may have led to low efficiency and poor transient response. The proposed fuzzy tuning mechanism is used to avoid this problem. Computer simulations confirm the effectiveness of the proposed control method.

A new current model flux observer for wide speed range sensorless control of an induction machine

A new closed loop current model flux observer is designed to estimate the rotor flux, position and velocity of an induction machine. The current observer includes carefully designed sliding mode functions which are derivative of the fluxes along the /spl alpha/ and /spl beta/ axes. Therefore, when the estimated current converges to the measured one, the flux estimation is a mere integration of the sliding mode function. The rotor speed can then be derived from the sliding mode functions and the estimated flux. In the current and flux observers all of the terms that contain the rotor time constant and the rotor speed have been replaced by the sliding mode functions, thus making the proposed current and flux estimations completely insensitive to the rotor time constant variation and any error in the estimated speed. Simulations and experiments are performed under a variety of conditions to validate the effectiveness of the proposed algorithm.

Adaptive estimation of rotor time constant for indirect field-oriented induction motor drive

A novel estimation model based adaptive control for indirect field-oriented induction motor drive is presented. A new coordinate reference frame is utilised to describe the dynamical model of an induction motor. Then, the new reference frame based estimator is proposed to adaptively estimate the redefined state variables and the rotor time constant, necessarily used in indirect field-oriented control. Moreover, a modified estimation model also based on the same reference frame is further presented to simplify the estimation and adaptation computation. By utilisation of the estimation approach, robust indirect-field-oriented control with respect to rotor time constant variation due to the effect of thermal changes is obtained. Finally, simulation and experimental results demonstrate the validity of the approach for practical applications.

Field oriented control of induction machines employing rotor end ring current detection

The usual method of induction motor torque control uses the indirect field orientation principle in which the rotor speed is sensed and slip frequency is added to form the stator impressed frequency. Unfortunately, the rotor resistance varies as the motor heats up under load thereby changing the rotor time constant which has a deleterious effect on the torque response. In this paper two new field oriented control schemes are presented which employ rotor end ring current detection and thereby remove the dependence of the controller accuracy on temperature so that the controller is entirely independent of rotor time constant variations. The field orientation schemes do not require an incremental encoder for rotor position sensing. The motor torque can be accurately controlled even down to zero speed operation. >