Mohamed S. Zaky

Wide-Speed-Range Estimation With Online Parameter Identification Schemes of Sensorless Induction Motor Drives

Recently, the development of speed estimation methods for sensorless control of induction motor drives has found great interest in the research community. Parameter adaptation schemes play an important role for better speed estimation over a wide range from zero to high levels beyond the rated speed. Therefore, parallel identification schemes for both speed and stator resistance of sensorless induction motor drives are proposed for a wide range of speed estimation. These estimation algorithms combine a sliding-mode current observer with Popovs hyperstability theory. Low- and zero-speed operations of the proposed sliding-mode-observer (SMO)-based speed estimation combined with an online stator resistance adaptation scheme are investigated. A modified SMO-based speed estimation scheme for field-weakening operation is also introduced. The mismatch problem of magnetizing inductance in the field-weakening region is treated by an online identification scheme. Magnetizing inductance, estimated in this way, is further utilized within the SMO, so that the main flux saturation variation is taken into consideration. The performance of the proposed SMO and its speed estimation accuracy, with an indirect field-oriented controlled induction motor, are verified by simulation and experimental results over a wide speed range from zero to high values beyond the base speed.

Stability Analysis of Speed and Stator Resistance Estimators for Sensorless Induction Motor Drives

This paper presents an analysis by which the stability of a multiple-input-multiple-output system of simultaneous speed and stator resistance estimators for sensorless induction motor drives can be successfully predicted. The instability problem of an adaptive flux observer (AFO) is deeply investigated. In order to achieve stability over a wide range of operation, a design of the observer feedback gain is proposed. Furthermore, closed-loop control systems of the independent use of the two estimators are developed. Therefore, all gains of the adaptive proportional-integral controllers are selected and generalized to provide good tracking performance as well as fast dynamic response. The performance of the AFO using the proposed gains, with a sensorless indirect-field-oriented-controlled induction motor drive, is verified by simulation and experimental results. The results show a good improvement in both convergence and stability, particularly in the regenerative mode at low speeds, which confirm the validity of the proposed analysis.

A Performance Investigation of a Four-Switch Three-Phase Inverter-Fed IM Drives at Low Speeds Using Fuzzy Logic and PI Controllers

This paper presents a speed controller using a fuzzy-logic controller (FLC) for indirect field-oriented control (IFOC) of induction motor (IM) drives fed by a four-switch three-phase (FSTP) inverter. In the proposed approach, the IM drive system is fed by an FSTP inverter instead of the traditional six-switch three-phase (SSTP) inverter for cost-effective low-power applications. The proposed FLC improves dynamic responses, and it is also designed with reduced computation burden. The complete IFOC scheme incorporating the FLC for IM drives fed by the proposed FSTP inverter is built in MATLAB/Simulink, and it is also experimentally implemented in real time using a DSP-DS1103 control board for a prototype 1.1-kW IM. The dynamic performance, robustness, and insensitivity of the proposed FLC with the FSTP inverter-fed IM drive is examined and compared to a traditional proportional-integral (PI) controller under speed tracking, load disturbances, and parameters variation, particularly at low speeds. It is found that the proposed FLC is more robust than the PI controller under load disturbances, and parameters variation. Moreover, the proposed FSTP IM drive is comparable with a traditional SSTP IM drive, considering its good dynamic performance, cost reduction, and low total harmonic distortion (THD).

Sensorless Torque/Speed Control of Induction Motor Drives at Zero and Low Frequencies With Stator and Rotor Resistance Estimations

Stability, robustness, and estimation accuracy of the adaptive flux observer (AFO) for sensorless induction motor (IM) drives are the most critical issues at zero and very low frequencies. In this paper, the design of speed, stator resistance, and rotor resistance estimators, to improve the robustness of AFO to parameters variation, is proposed. These estimators are arranged to have a cascade multi-input multi-output structure, and simplified to a single-input single-output structure for stability analysis and gain selections. To design both the observer feedback gains and adaptive proportional-integral gains, the stability conditions of the estimators are derived to guarantee a stable AFO in all the four quadrants of operation. The sensitivity analysis against stator and rotor resistance variations is also provided. The detailed analytical, simulation, and experimental results are presented to validate the proposed AFO of sensorless IM drives in torque- and speed-controlled modes of operation, particularly at zero and very low frequencies.

High Dynamic Performance of Interior Permanent Magnet Synchronous Motor Drives Based on Feed-forward Load Torque Compensator

Abstract This article presents an improvement in the dynamic performance of interior permanent magnet synchronous motor drives by using a feed-forward load torque compensator along with a proportional-integral speed controller. In such a case, the load torque estimator compensates the speed control by setting a feed-forward torque value through the q-axis current reference value, so that the machine speed can reach the reference speed very fast. The experimental and simulation results indicate that the proposed control technique improves the interior permanent magnet synchronous motor speed performance in terms of tracking precision and travel time. Moreover, the performance of an interior permanent magnet synchronous motor drive system using a conventional proportional-integral controller is compared with the proposed controller. The results show that the proposed proportional-integral controller with a feed-forward load torque compensator has achieved superior performance compared to those of the conventional one. An acceptable speed response under load torque variations and parameter uncertainty is found.

Adaptive Switching Plane of Integral Variable Structure Control for Speed Control of Permanent Magnet Synchronous Motor Drives

Abstract This article presents a robust speed controller for field-oriented controlled permanent magnet synchronous motor drives. The proposed controller is designed using integral variable structure control combined with a linear quadratic regulator. The linear quadratic regulator scheme is used to decide the optimal feedback gain to shape the system dynamics by tuning the integral variable structure control switching plane to guarantee the robustness of the control algorithm in both reaching and sliding phases. The complete drive is implemented in real time using a digital signal processor control board (DS1102, Texas Instruments, dSPACE GmbH, Germany). The tracking properties and robustness of the proposed scheme are examined through both simulations and experimental work. It guarantees accurate control performance in the presence of parameter variation, step speed change, and load disturbances. The performance of the permanent magnet synchronous motor drive system with a conventional proportional-integral controller is presented in comparison with the proposed controller. The results show a significant improvement in both the transient and steady-state responses over the conventional proportional-integral controller.

Design of Multiple Feedback Control Loops for a Single-phase Full-bridge Inverter Based on Stability Considerations

Abstract Single-phase inverters employ LC filters for the purpose of reducing pulse-width modulation harmonics. The drawback of LC filter is its stability problem at resonance frequency. Passive damping offers simple and reliable solution, but it decreases the overall system efficiency. Active damping is lossless and provides flexibility of controlling the damping performance; however, it is sensitive to parameters variation. This article presents stability analysis of a single-phase full-bridge inverter to improve dynamic performance and stability. Design of LC filter is carried out considering both undamped and damped structures. The effect of filter parameters on pole-zero locations of the inverter is presented, and variation of the phase margin over a wide range of parameters variation is examined. Active damping using closed-loop current control of the full-bridge inverter to mitigate the resonance oscillation is designed and compared with passive damping. The disturbance rejection via dynamic stiffness with and without active damping is examined to justify the proposed current controller. Simulation and experimental results are presented to validate the effectiveness of the proposed design. It is found that the proposed control of the inverter provides excellent voltage regulation with low total harmonic distortion and ensures good performance and robust stability under parameters variation.

Gain Scheduling Adaptive Proportional-integral Controller for a Field-oriented Control of Hybrid Stepper Motor Drives

Abstract This article presents a gain-scheduling adaptive proportional-integral speed controller for field-oriented control of hybrid stepper motor drives. The proportional-integral gains are designed to be a function of the speed error and are allowed to vary within a pre-determined range. This, therefore, eliminates the problems suffered by the conventional proportional-integral controller. The performance of the proposed gain-scheduled proportional-integral controller with field-oriented control is simulated and compared with that of the conventional fixed proportional-integral controller under starting, speed reversal, repetitive operation, and parameter variations, as well as load disturbances. The experimental system of the hybrid stepper motor drive is implemented using a digital signal processor DS1102 control board (Texas Instruments, dSPACE GmbH, Germany) to examine and evaluate the performance criterion of the proposed controller under different operating conditions. Simulation and experimental results show good improvement in transient as well as steady-state responses of the proposed controller over the conventional fixed proportional-integral one. Moreover, field-oriented control of a hybrid stepper motor modifies the dynamic performance and current distortion rather than the stepping mode of the open-loop control system.

Robust Sliding Mode Speed Controller-based Model Reference Adaptive System (MRAS) and Load Torque Estimator for Interior Permanent Magnet Synchronous Motor (IPMSM) Drives

Abstract This paper presents a robust sliding mode control (SMC)-based model reference adaptive system (MRAS) aimed at improving the dynamic performance of interior permanent magnet synchronous motor (IPMSM) drives. MRAS following a speed controller for IPMSM drives is developed. The error signal between the plant speed and MRAS speed is augmented to permit the prescribed specifications be maintained using SMC. The load disturbance is detected using a load torque estimator and is compensated through the q-axis current reference value. The load torque estimator is used to provide a feedforward value in the speed controller in order to decouple the load torque from the speed control. This method can improve IPMSM dynamic performance against the disturbance torque without increasing SMC gain due to both chattering and stability limitations. The complete field-oriented control of an IPMSM drive with the proposed controller is successfully implemented in real time using the DSP-DS1102 control board for a laboratory 1-hp motor. A performance comparison of the proposed controller with the conventional PI controller is also provided. The efficacy of the proposed controller is verified by simulation and experimentation under different operating conditions. It is found that the proposed controller provides an excellent speed response under load torque disturbance and parameter uncertainty.

Power Factor Correction of Four-Switch Three-Phase Inverter-Fed Sensorless Induction Motor Drives with Partial Electrical Free Measurement

Abstract In this article, a novel partial electrical free measurement method to improve the power-factor of four-switch three-phase (B4) inverter for sensorless induction motor drives is proposed. This method uses a simple-free of measuring current or voltage for the power factor correction circuit. The proposed controller of the B4 inverter improves the power factor to be closed to a unity with a high power quality performance and with a minimum total harmonic distortion of the supply current. The complete drive system is carried out utilizing Matlab/Simulink. Also, it is executed in real-time using a prototype system composed of a dSPACE DS-1104 digital control board and a laboratory 1.1 kW three-phase squirrel cage induction motor. The simulation and experimental waveforms prove the efficacy of the proposed drive system under various operating conditions. It is found that the proposed drive system has a reduced number of switches and sensors with a minimum cost which suitable for low commercial power applications. Moreover, it enhances noise isolation between power circuit and controller.