Field Oriented Speed Control Research Articles

One-Instant Flux Observer design for Three-Phase induction motor with reduced bound active load rejection speed controller.

Latency in flux observation has an adverse effect on the performance of observer-based field-oriented speed control for three-phase induction motor (IM). The reduction of the convergent rate of estimation errors could improve the performance of speed-controlled IM based on flux observers. The main contribution is to design a fast convergent flux observer, which provides bounded estimation error immediately after one instant of motor startup. The proposed flux observer fused barrier function adaptive mechanism with integral sliding mode control principle to yield BFISMO. Rigorous stability analysis has been conducted to achieve global flux estimation error ultimate boundedness. Moreover, three controllers have been designed. The first control design is devoted to flux control based on a backstepping controller, while the other two controllers' design is dedicated to rotor speed control of the motor. The speed controller is developed by combining the backstepping control with disturbance observers to estimate the unmatched load torque named quasi-sliding mode observer (QSMDO), and nonlinear disturbance observer (NLDO). Based on numerical simulations, the performance and efficacy of the proposed BFISMO have been assessed by conducting a comparison study to other observer techniques. The results showed the superiority of the proposed observer over the conventional versions.

Improving energy efficiency and economics of motor-pump-system using electric variable-speed drives for automatic transition of working points

This work investigates the energy saving in a multi-water-pump system with two advanced electric variable speed drive (EVSD) techniques (i.e., multi-pump-single-drive (MPSD) and multi-pump-multi-drive (MPMD)) for controlling the water head and flow; and moreover, for specifying the candidate number of work pumps, and moreover the number of ON pumps with MPSD or MPMD. These techniques are based on field-oriented speed control of induction motor (IM) for driving the motor-pump set. To save energy, the working point of motor-pump set is moved from the uneconomic rates to the most efficient head and flow rates. The new point is located at a modified performance curve for achieving the target flow and head. In contrast with referenced techniques, the consumed power is just enough for that transition with no excessive flow and/or head. The suggested drive technique is verified via simulation results. Moreover, dynamic performance of the pump-motor set is assessed at diverse conditions of flow and head. Accordingly, a comparison between MPSD and MPMD is presented at different speeds with efficiency analysis at rated operating point. The efficiency is increased, and energy is saved with MPMD system. Experiments validate the effectiveness of the adopted IM drives when the operating point is transitioned at different load circumstances.

Performance Improvements of Induction Motor Drive Supplied by Hybrid Wind and Storage Generation System Based on Mine Blast Algorithm

This research investigates the performance improvements of induction motor (IM) drive supplied by a hybrid wind/battery storage system based on the optimal mine blast algorithm. This is done by using IM field-oriented speed control as an independent dynamic load and a battery as a storage power unit. To ensure the accuracy and quality of energy equilibrium in autonomous wind power systems, there is an urgent and necessary demand for battery storage units. So in principle, the overall system of the complete model is configured to be combined with an uncontrolled rectifier, a steady magnetic synchronous generator (PMSG), a buck converter, and a lead–acid battery (LAB) in addition to an induction motor. According to the imposed controller, the loads required power can be obtained effectively by the prescribed battery storage and the wind generation units. Considering the suggested vector control to adjust the induction motor velocity through a three-phase inverter, it will be obtained 220 V/50 Hz, which is the principal target of this research. Moreover, the system with the proposed optimal control is compared with the optimal control based on genetic algorithm (GA) and the classical PID control. It is, therefore, possible to conclude that the results of numerical calculations and simulations illustrate that the studied system has strong achievement and perfect predictor of the electric parameter waveforms.

Effects to System Performance of Different PWM Techniques in Field Oriented Speed Control with back-to-back Converter of PMSG

In this paper, the performance of space vector pulse width modulation (SVPWM), sinusoidal pulse width modulation (SPWM) and hysteresis current control (HCC) techniques used in speed control with back to back converter of permanent magnet synchronous generator (PMSG) used in wind turbines are comparatively analyzed. The comparative analysis includes dynamic response, total harmonic distortion (THD), torque ripple and current ripple. Furthermore, SVPWM and SPWM are compared in terms of the using DC link voltage. Analysis of system is realized with MATLAB/Simulink program. PMSG used in simulations is surface mounted, bipolar and its power is 1.8 kW. Also, the energy of PMSG is transferred to grid with Field Oriented Control (FOC). According to analysis results, it has been observed that SVPWM generally has more effective results than both HCC and SPWM control techniques. Finally, it is observed that SVPWM can produce about 15 percent higher than SPWM in output voltage.

Online Stator Interturn Short Circuits Monitoring in the DFOC Induction-Motor Drive

This paper deals with monitoring of interturn short circuits of induction-motor (IM) stator windings operating under the direct field-oriented control (DFOC). Time transients are presented to illustrate the performance of the field-oriented speed control under the stator-winding damage. Novel detection algorithm is introduced, based on an analysis of the internal signals from the control structure: controller outputs and control path decoupling variables. The spectral analysis of these signals is used to detect the stator-winding incipient damages. Significant changes of the constant component ${f}_{{dc}}$ and the double-fundamental harmonic component $\text{2}{f}_{s}$ observed in these signals’ spectra under the stator-winding failure become the basis for the failure diagnostics in various operating conditions of the DFOC IM drive. The superiority of the proposed detection algorithm over the classical motor current signature analysis (MCSA) method is described. The online monitoring process is shown. Simulation and experimental results are presented to validate the proposed detection algorithm.

Speed Observer and Reduced Nonlinear Model for Sensorless Control of Induction Motors

We consider field-oriented speed control of induction motors without mechanical sensors. We augment the traditional approach with a flux observer and derive a sixth-order nonlinear model that takes into consideration the error in flux estimation. A high-gain speed observer is included to estimate the speed from field-oriented currents and voltages. The observer design is independent of the feedback controller design. By high-gain-observer theory, we define a virtual speed output for the sixth-order nonlinear model, which can now be used to design a feedback controller whose performance is recovered by the speed observer when the observer gain is chosen high enough. We then focus on the traditional field oriented control (FOC) approach where the flux is regulated to a constant reference and high-gain current controllers are used. By designing a flux regulator to maintain the flux at a constant reference, and a current regulator to regulate the q-axis current to its command, we derive a third-order nonlinear model that captures the essence of the speed regulation problem. The model has the speed and two flux estimation errors as the state variables, the q -axis current as the control input, and the virtual speed as the measured output. It enables us to perform rigorous analysis of the closed-loop system under different controllers, and under uncertainties in the rotor and stator resistances and the load torque. In this paper, we emphasize the design of feedback controllers that include integral action. The analysis reveals an important role played by the steady-state product of the flux frequency and the q-axis current in determining the control properties of the system. The conclusions arrived at by using the reduced-order model are collaborated by simulation and experimental results.

Speed sensorless field-oriented control of induction motor with interconnected observers: experimental tests on low frequencies benchmark

Field-oriented speed control of induction motors (IMs) without mechanical sensors (speed sensor and load torque sensor) are considered. The methodology is divided into two parts. First, interconnected high-gain observers are designed to estimate the mechanical and magnetic variables from the only measurement of stator current. Secondly, the speed and flux estimation are used by a controller to achieve the speed/flux tracking. The flux regulation problem is simple and the traditional approach is followed by using proportional integral (PI) controller. For the speed-regulation problem, it is stated that flux regulation quickly happens by using a high- gain PI controller to regulate the g-axis current to its reference. Stability analysis based on Lyapunov theory is proved to guarantee the 'observer + controller' stability. To test and validate the controller-observer by considering the sensorless control problem of IM at low frequency, a significant benchmark is implemented. The trajectories of this benchmark are designed to validate the controller and observer under three operating conditions: low speed, high speed and very low speed. Furthermore, robustness tests with respect to parameter variations are given in order to show the performance of the proposed observer-controller scheme.

Global asymptotic stability of indirect field-oriented speed control of current-fed induction motors

In this short paper, we show that the indirect field-oriented controller for current-fed induction motors guarantees the global asymptotic stability of speed tracking error for time-varying speed and rotor flux references. The load torque is assumed to be constant but is unknown.

Online estimation of stator resistance of an induction motor for speed control applications

Speed control of induction motors requires the accurate estimation of the fluxes in the motor. But the flux estimate, when estimated from the stator circuit variables, is dependent on the stator resistance of the induction motor. As a consequence, the flux estimate is prone to errors due to variations in the stator resistance, especially at low stator frequencies. A scheme is presented in this paper for an online estimation of the stator resistance under steady state operating conditions, using variables that can be measured from the terminals of the motor alone. The scheme is based on estimating the steady-state magnitudes of the stator and rotor flux space phasors using the reactive power. An analysis of the effect of the stator resistance variations on the flux estimate is presented. A simulation of a rotor field oriented speed control of a VSI-fed induction motor using stator circuit variables is performed incorporating the online stator resistance estimation strategy.

Software Pulsewidth Modulation for μP Control of AC Drives

The on-line pulsewidth modulation (PWM) of a voltage source inverter for converter-fed ac drives is presented. The modulation is realized by software, thus allowing a direct interface between the microprocessor-based speed control and the on-off commands for the inverter. An efficient modulation technique is achieved by asynchronous switching of the inverter phases; a current control loop provides fast feedback, so that a fast step response of the stator currents can be obtained. All control functions, including field-oriented speed control of an induction motor, are performed by a 16-bit microprocessor. Experimental results obtained with a 22-kW induction motor prove that the proposed scheme provides a very good performance of the drive from standstill up to the field weakening range.