Speed observer system for advanced sensorless control of induction motor

This paper presents a sensorless control system for induction motors, which is realized on a fixed-point digital signal processor (DSP) and field programmable gate arrays (FPGAs). An observer system has been developed for estimation of speed and the other state variables. The proposed observer system is verified for different conditions of motor operation. Experimental results for the control system fed by voltage source inverter controlled using predictive current controller are presented.     

Speed control of a PV powered DC motor driving a self-excited3-phase induction generator for maximum utilization efficiency

Photovoltaic (PV) powered DC motors driving dedicated loads (e.g. water pumps) are increasingly used in the remote rural areas of many developing countries. The key to their success is simplicity (direct coupling, no DC-AC conversion, no storage batteries, etc.). Because of the relatively high cost of the PV array, the system designer is interested in maximizing its utilization efficiency. A PV powered DC motor can also be used to drive a three-phase self-excited induction generator (SEIG). This arrangement is useful as part of an integrated renewable energy system (IRES), which takes advantage of the inherent diversity of wind and solar energy in most developing countries to improve power quality. The SEIG is driven by a wind-turbine, DC motor, or both. Another advantage of this arrangement is its versatile control characteristics through the DC motor control. This paper describes a technique to maximize the utilization efficiency of the PV array by controlling the field current of the DC motor through a DC chopper     

Speed control of a three-phase induction motor based on robust optimal preview control theory

A synthesized method for speed control of a three-phase induction motor (IM) based on optimal preview control system theory is implemented in this article. An IM model comprises three-input variables and three-output variables that coincide with the synchronous reference frame that is implemented using the vector method. The input variables of this model are the stator angular frequency and the two components of the stator space voltage vector, whereas the output variables are the rotor angular speed and the two components of the stator space flux linkage. The objective of the synthesized control system is to achieve motor speed control, field orientation control, and constant flux control. A novel error system is derived and introduced into the control law to increase the robustness of the system. The preview feed-forward controller, which includes the desired and disturbance signals, is used to improve the transient response of the system. A space vector pulse-width modulation (PWM) control technique for voltage source-fed IM is prepared for microprocessor-based control. Spectral analysis of the output voltage is evaluated to predict the effect of the proposed space vector modulation technique on the dynamic performance of the IM. The optimal preview controlled system is implemented, and its applicability and robustness are demonstrated by computer simulation and experimental results.     

Performance enhancement of an induction motor by secondaryimpedance control

The paper demonstrates the use of nonresistive secondary control of an induction motor to improve efficiency, power factor and torque. A mathematical algorithm is presented to predict the control requirements in terms of secondary capacitance. The required secondary capacitance is implemented by a novel electronic switching technique that effectively increases the value of the used capacitor. This overcomes the high-capacitance demand and provides a feasible solution. Experimental verification is presented in the results obtained from a small induction motor drive     

A rule-based acceleration control scheme for an induction motor

This paper presents a rule-based acceleration control scheme that aims to give an inverter-fed induction motor excellent dynamic performance. In every time interval of the control process, the acceleration increments produced by two different voltage vectors are compared, yielding one optimum stator voltage vector which is selected and retained. The online inference control is built using a rule-based system and some heuristic knowledge about the relationship between the motor voltage and acceleration. Because evaluation of integrals is not required and the motor parameters are not involved, the new controller has no accumulation error due to the integrals as in the conventional vector control schemes and the same controller can be used for different motors without modification     

A new composite adaptive speed controller for induction motor basedon feedback linearization

A new adaptive control technique is proposed to control the speed of the induction motor in this paper. First, the rotor flux is estimated with the simplified rotor flux observer on the rotor reference frame and the feedback linearization theory is used to decouple the rotor speed and the flux amplitude. Then, a new composite adaptive control algorithm based on an integral cost function is designed to control the speed of the induction motor. The overall speed control system is verified to be stable and robust to the parameter variations and external disturbances. Experimental results are provided to demonstrate the effectiveness of the presented approach. The good speed tracking and load regulating responses can be obtained by the proposed controller     

Field assessment of induction motor efficiency through air-gaptorque

Induction motors are the most popular motors used in industry. This paper further suggests the use of the air-gap torque method (see J.S. Hsu et al., ibid., vol.10, no.3, p.471-7, 1995) to evaluate their efficiency and load changes. The fundamental difference between Method E and the air-gap torque method is discussed. Efficiency assessments conducted on induction motors under various conditions show the accuracy and potential of the air-gap torque method     

In-situ induction motor efficiency determination using the geneticalgorithm

Numerous methods exist for determining the efficiency of induction motors. Many of them require a no-load test, which is not possible for in-situ determination. The evaluation of motor efficiency based on the motor's nameplate or manufacturer's data, on the other hand, in many cases cannot ensure a fair assessment of induction motors employed in the plant. An extensive survey of techniques for efficiency measurement is given. A new method is proposed for in-situ induction motor efficiency determination, based on the genetic algorithm. Results are compared with torque-gauge results     

Adaptive fuzzy-neural-network control for induction spindle motor drive

An induction spindle motor drive using synchronous pulse-width modulation (PWM) and dead-time compensatory techniques with an adaptive fuzzy-neural-network controller (AFNNC) is proposed in this study for advanced spindle motor applications. First, the operating principles of a new synchronous PWM technique and the circuit of dead-time compensator are described in detail. Then, since the control characteristics and motor parameters for high-speed-operated induction spindle motor drive are time varying, an AFNNC is proposed to control the rotor speed of the induction spindle motor. In the proposed controller, the induction spindle motor-drive system is identified by a fuzzy-neural-network identifier (FNNI) to provide the sensitivity information of the drive system to an adaptive controller. The backpropagation algorithm is used to train the FNNI online. Moreover, the effectiveness of the proposed induction spindle motor-drive system is demonstrated using some simulated and experimental results.     

Self-tuning control of induction motor drive using neural networkidentifier

This study presents a new self-tuning PI speed controller with load torque observer and feedforward compensation based on neural network identification for an induction motor. A two-layer neural estimator is also used to provide a real-time adaptive estimation of the unknown motor dynamics. The widely used projection algorithm is used as the learning algorithm for this network, to minimize the difference between the motor's actual response and that predicted by the neural estimator. The proposed neural estimator uses this learning to adjust PI speed controller with a load torque observer to generate the control signal online, thereby bringing the motor output to a desired reference trajectory. The theoretical analysis, simulation and experimental results demonstrate the proposed scheme's effectiveness     

Temperature rise of an induction motor during plugging

The problem of three-dimensional transient heat flow in the stators of induction motors is solved using a finite-element formulation employing arch-shaped elements. The shape functions and exact solutions are derived algebraically for the utmost economy in computation. The temperature distribution has been determined considering convection from the surface and the two ends. The temperature distribution has also been determined by specifying the temperature of the surface and the ends. A simple cylinder is used as an example. The temperature at different locations in the stator of the induction motor has been computed during transients     

On-site efficiency evaluation of three-phase induction motor based on particle swarm optimization

On-site efficiency determination of induction motor is essential in industrial plants for saving the energy consumption. This paper presents a new application of particle swarm optimization (PSO) approach for field efficiency evaluation of induction motor based on a modified induction motor equivalent circuit. The stray-load loss is considered in the equivalent circuit by adding an equivalent resistor in series with the rotor circuit and its value is derived from the assumed stray-load loss recommended in IEEE Std. 112. The PSO approach uses the information about the stator current, stator voltage, input power, stator resistance and speed of the motor and determines the equivalent circuit parameters. Once these parameters are known, the efficiency of motor can be evaluated. The simulation results on a 3.75 kW motor are presented and compared with the results of torque gauge method (TGM), equivalent circuit method (ECM), slip method (SM), current method (CM) and segregated loss method (SLM). The results reveal that the proposed method can evaluate the efficiencies of motor with less than 3% error under normal load conditions. Consequently, the method can be used in motor energy management system for improving the overall energy savings in industry.     

Design and implementation of PLC-based monitoring control system for induction motor

The implementation of a monitoring and control system for the induction motor based on programmable logic controller (PLC) technology is described. Also, the implementation of the hardware and software for speed control and protection with the results obtained from tests on induction motor performance is provided. The PLC correlates the operational parameters to the speed requested by the user and monitors the system during normal operation and under trip conditions. Tests of the induction motor system driven by inverter and controlled by PLC prove a higher accuracy in speed regulation as compared to a conventional V/f control system. The efficiency of PLC control is increased at high speeds up to 95% of the synchronous speed. Thus, PLC proves themselves as a very versatile and effective tool in industrial control of electric drives.     

Passivity-based sliding mode position control for induction motor drives

In this paper, a passivity-based sliding-mode controller is proposed to control the motion of an induction motor. At first, the induction motor is proved to be a state strictly passive system. Then, a sliding-mode position controller with an adaptive load torque estimator is designed to control the position of the induction motor such that the chattering effects associated with a classical sliding-mode position controller can be eliminated. The stability analysis of the overall position control system is carried out by the passivity theory. The proposed approach is robust with regard to variations of motor mechanical parameters and load torque disturbances. Finally, experimental results are included to demonstrate that good position tracking can be obtained without the rotor flux observer.     

Combined vector control and direct torque control method for high performance induction motor drives

A new control method is proposed for three phase high performance induction motor drives. The control system enjoys the advantages of vector control and direct torque control and avoids some of the implementation difficulties of either of the two control methods. In particular, the proposed control system includes a current vector control in connection with a switching table. An extensive comparative performance evaluation of a motor under the proposed control method confirms the effectiveness of the method and its partial superiority over either vector control or direct torque control despite its relative structural simplicity.     

Optimal efficiency speed control of induction motors by variablerotor impedance

An optimal method to control the speed of a wound-rotor induction motor by variable external rotor impedance is presented. The rotor impedance is adjusted so that, for any desired torque and slip values, the total copper losses are minimized. Motor efficiency is improved compared with the case of conventional speed control by variable rotor resistance only. An example illustrates the copper loss reduction and dynamic behavior of the drive. Simulation study results that show the percentage copper loss reduction is generally likely to be higher for lighter loads. For constant-torque loads, the reduction percentage reaches a peak at the lower slip values, whereas for fan-type loads the most significant percentage copper-loss reduction occurs at both the higher and lower slip values. The response time of the rotor speed for startup or a sudden change in the speed setting is considerably smaller than that achieved by pure rotor resistance control     

Efficiency increase of an induction motor by improving coolingperformance

Improving the efficiency of induction motors, which are the most energy consuming electric machines in the world, saves much energy. The efficiency can be increased by improving cooling performance as well as by using better materials or by improving electromagnetic performance with better design. This paper presents the relationship between the efficiency or the losses and the temperature of coils with experiments as well as simulations by changing parameters such as the load and the flow rate of cooling air. The losses and the efficiency are calculated from an equivalent circuit method as well as experiments. Coil temperatures variation affects much on the efficiency. The internal cooling method is better than that of external cooling for the coil temperature reduction. Several cooling methods are compared focusing on the fan efficiency and performance, from which the values of the efficiencies of the motors are expected. The fan efficiency as well as the fan performance should be considered for the optimum fan design to increase the total efficiency of a motor. The simulations are validated by the comparison with the experiments     

On local linearization of control systems

We consider the problem of topological linearization of smooth (C ^∞ or C ^ω) control systems, i.e., of their local equivalence to a linear controllable system via point-wise transformations on the state and the control (static feedback transformations) that are topological but not necessarily differentiable. We prove that the local topological linearization implies the local smooth linearization, at generic points. At arbitrary points, it implies the local conjugation to a linear system via a homeomorphism that induces a smooth diffeomorphism on the state variables, and, except at “strongly” singular points, this homeomorphism can be chosen to be a smooth mapping (the inverse map needs not be smooth). Deciding whether the same is true at “strongly” singular points is tantamount to solve an intriguing open question in differential topology.     

A microcomputer-based induction motor drive system using currentand torque control

This paper proposes an induction motor drive with current and torque control. The current control based on the current error with the current controller yields h_l signal. The torque control based on the torque error with the torque controller yields a h_l signal. According to the h_l signal, the h_l signal and the appropriate voltage vector is selected by using a look-up table to control the induction motor drive to obtain a rapid speed response. The torque controller, current controller, and d-q frame transform are constructed by the hardware which reduce the running time of the microcomputer to obtain a high performance drive. Computer simulations and experimental results demonstrate that the proposed method can obtain a high performance induction motor drive. Meanwhile, employing the advantages of the added zero voltage vector to reduce the inverter switching frequency greatly increasing the efficiency of the inverter     

Optimal efficiency control strategy for interior permanent-magnet synchronous motor drives

In this paper, the problem of efficiency optimization in vector-controlled interior permanent-magnet (PM) synchronous motor drives is investigated. A loss model controller is introduced that determines the optimal d-axis component of the stator current that minimizes power losses. For the implementation of the suggested controller, the knowledge of the loss model is not required since an experimental procedure is followed to determine its parameters. Furthermore, it is shown that the loss model of the interior PM motor can be used as a basis for deriving loss minimization conditions for surface PM synchronous motors and synchronous reluctance motors as well. Experimental results of an interior PM motor are presented to validate the effectiveness of the proposed method and demonstrate the operational improvements.