Direct Field-oriented Control System Research Articles

Application of Super-Twisting Sliding Mode Controllers in Direct Field-Oriented Control System of Six-Phase Induction Motor: Experimental Studies

Abstract This paper presents the direct field-oriented control (DFOC) method of six-phase induction motor with the application of super-twisting sliding mode algorithm. The mathematical model of the six-phase induction motor has been described. The descriptions of the space vector modulation (SVM) method and the super-twisting algorithm have been presented. The DFOC method with super-twisting sliding mode controllers has been described. The experimental studies of the DFOC method with super-twisting controllers have been performed, and the results of these studies are presented and discussed.

Field-oriented control of five-phase induction motor with open-end stator winding

Abstract The mathematical model of the five-phase squirrel-cage induction motor and the system of the dual five-phase voltage source inverter have been presented. The control methods and control systems of the field-oriented control of the five-phase induction motor with an open-end stator winding are described. The structures of the direct fieldoriented control system (DFOC) and the Indirect Field-oriented control system (IFOC) with PI controllers in outer and inner control loops are analyzed. A method of space vector modulation used to control the system of the dual five-phase voltage source inverter has been discussed. The results of simulation studies of the field-oriented control methods are presented. Comparative analysis of the simulation results was carried out.

FPGA-Based Real-Time Emulation of Power Electronic Systems With Detailed Representation of Device Characteristics

This paper presents a field-programmable gate array (FPGA)-based real-time digital simulator for power electronic apparatus based on a realistic device-level behavioral model. A three-level 12-pulse voltage source converter (VSC)-fed induction machine drive is implemented on the FPGA. The VSC model is computed at a fixed time step of 12.5 ns, allowing a realistic representation of insulated-gate bipolar transistor (IGBT) nonlinear switching characteristics and power losses. The simulator also models a squirrel-cage induction machine, a direct field-oriented control system, and a pulsewidth modulator to achieve the real-time simulation of the complete drive system. All the models have been implemented using very high speed integrated circuit hardware description language (VHDL). Real-time simulation results have been validated using the measured device-level IGBT characteristics.

High-performance sensorless vector control of induction motor drives using artificial intelligent technique

This paper presents a sensorless speed observer method of an induction motor using an artificial intelligent technique in direct field-oriented control system. The proposed sensorless vector control system consist of an adaptive observer of rotor flux in order to accurately estimate stator resistance and speed simultaneously, without affecting drive performances. The observer is associated with a direct vector control drive to rotor flux orientation for induction motor and uses the stator voltages and currents as inputs. To improve performance in a wide operating range, and achieve low sensitivity to parameter variations and external influences, the system uses an intelligent adaptive mechanism based on fuzzy logic approach to estimate the speed and a simple PI controller to determinate the stator resistance. The algorithm developed is robust and effective; it also provides accurate estimates, a good trajectory tracking with the different dynamics presented. Numerical experiments are presented to illustrate the feasibility of the proposed technique. Copyright © 2010 John Wiley & Sons, Ltd.

Real-Time Digital Hardware Simulation of Power Electronics and Drives

This paper presents a digital hardware realization of a real-time simulator for a complete induction machine drive using a field-programmable gate array (FPGA) as the computational engine. The simulator was developed using Very High Speed Integrated Circuit Hardware Description Language (VHDL), making it flexible and portable. A novel device-characteristic based model suitable for FPGA implementation has been proposed for the 2-level 6-pulse IGBT-based voltage-source converter (VSC). The VSC model is computed at a fixed time-step of 12.5 ns allowing a highly detailed and precise accounting of gating signals. The simulator also models a squirrel cage induction machine, a direct field-oriented control system, a space-vector pulse-width modulation scheme (SVPWM) and a measurement system. A multirate simulation of the system shows the slow (machine) as well as the fast (VSC and control) dynamic components. Real time simulation results under steady-state and transient conditions demonstrate modeling accuracy and efficiency

Stator-Core and Rotor-Core Losses Compensation for Direct-Field-Oriented Induction Motor

This paper focuses on a stator-core and rotor-core losses compensation technique devoted to a direct field-oriented control system of an induction motor incorporating parameter identification. The fundamental control algorithm is based on direct field orientation, which essentially requires rotor flux estimation using several motor parameters and detection of line currents and a rotor position. In order to suppress the flux estimation error caused by parameter mismatches, the magnetizing inductance and the rotor resistance are identified insensitively to the stator resistance by utilizing instantaneous reactive power. However, due to a model mismatch associated with the stator-core loss and rotor-core loss, neither the field orientation nor the parameter identification can be achieved as is expected, which mainly results in degradation of flux and torque control accuracy. This paper describes characteristics of the motor parameters precisely measured under various operating conditions, the influence of both stator-core loss resistance and rotor-core loss resistance on the field orientation and the parameter identification, and a compensation technique to obtain higher controllability than conventional field-oriented control techniques. Effectiveness of the proposed technique has been examined through experimental tests as well as computer simulations, and the absolute accuracy and linearity of the motor torque has been improved as a result.

Stability Analysis of the Direct Field Oriented Control System of the Induction Motor without a Speed Sensor using the Adaptive Rotor Flux Observer

The vector control of the induction motor without a speed sensor required the estimations of the rotor flux and the rotor speed. Since the estimations use the machine parameters and the stator voltage and current components as input quantities, the stability of the systems is sensitive to the variations of the machine parameters and the measured stator voltage errors and the current control errors compared with the vector control systems with a speed sensor.In this paper, the small signal stability analysis is carried out on the direct field oriented control system of the induction motor without a speed sensor using the adaptive rotor flux observer (MRAS method) and allows for the stability effects of the stator resistance and rotor resistance and the gain of the speed controller to be studied. The stability effects of the MRAS method are compared with that of the vector control system of the induction motor without a speed sensor based on _??_1q-feedback control (_??_1q-feedback method). Furthermore, theoreitical step responses of the rotor speed are compared with the experimental results.

A Method of Speed Sensorless Direct Field Oriented Control based on Flux Observer for Current Source Inverter Drive Induction Machine.

Many sensorless vector control systems have been proposed to increase the reliability and to reduce costs of the systems. However the parameters of an induction machine are changed by the temperature, the estimated speed may be incorrect value. When a constant torque drive system is constructed by a sensorless system and a current source inverter (CSI), the accuracy of the estimated speed influenced directly the response of the torque.In this paper, a direct field oriented control system is constructed by the flux observer which is low sensitivity to the rotor resistance variation and a proposed speed estimation scheme in a torque control system driven by a CSI. We compared experimental results by a voltage source inverter system and by the CSI system which is adopted our sensorless vector control scheme. At a lower speed condition, the system identifies the stator resistance, and we can estimate rotor speed correctly. Then the CSI system drives stably the induction machine without the speed sensor in a lower speed condition, and it can be applied to the constant torque drive systems.

Observers for field-oriented control of induction motor drives

One of the major problems associated with direct field-oriented control of induction motors is the sensitivity of the observer to variation of motor parameters. Various types of observer have been proposed but no complete study of sensitivities has been carried out. An analysis of the sensitivity of one class of observer, against the motor parameter variations, is presented. From the results of the analysis, a suitable observer is chosen and implemented as a part of a complete direct field-oriented control system. The results of the implementation are also presented. >

Direct Field Oriented Control of Induction Motor without Speed Sensors using Adaptive Flux Observer.

The field oriented control method is widely used for induction motor drives. In these applications, a speed sensor such as a shaft encoder is used. However, a speed sensor cannot be mounted in some cases such as motor drives in a hostile environment and high speed motor drives. Several field oriented control methods without speed sensors have been proposed. Most of them can be applied to only the indirect field oriented control but the direct field oriented control. And a stability has not been explained clearly.Therefore, a new method of estimating the induction motor speed based on the adaptive control theory is proposed. Characteristics of the direct field oriented control system with the proposed speed estimation scheme are verified by experiments. Further, the influence of the stator and rotor resistance variations on the speed estimation is analyzed, and its compensation method is also proposed.