A microcontroller-based induction motor drive system using variablestructure strategy with decoupling

The sliding-mode control concept is applied in the outer loop of a speed drive system utilizing a series-connected wound rotor induction machine (SCWRIM). A design procedure is outlined for the sliding-mode speed controller. The methods of decoupling and torque linearization for the SCWRIM are derived using the field-orientation as well as the torque angle control concepts. Sliding-mode control with cascaded integral operation is used to reduce torque chattering and steady-state error. Accelerator sliding lines are introduced to enable better utilization of the torque capability of the drive system. The parameter-insensitive response provided by this method of control is demonstrated. The effects on the dynamic and static performance with varying drive inertia and load disturbance are studied and compared with the conventional approach using PI control. The influences of sampling effects on sliding-mode control performance are also illustrated and discussed. Microcontroller-based implementation of the speed drive system is employed. Both simulation and experimental results are presented     

Gate drive level intelligence and current sensing for matrixconverter current commutation

This paper is concerned with the process of current commutation in matrix converters. The mechanisms involved in the commutation process are described and practical waveforms are presented. A novel commutation strategy is described that uses gate drive level intelligence in the form of a field-programmable gate array. Current direction is determined using device voltages and, therefore, the measurement problems associated with all other commutation methods are overcome. Practical results from an 18-kW matrix converter induction motor drive are presented     

Field-oriented control of an induction machine in a high frequencylink power system

A field-oriented controlled induction machine drive operating with a high-frequency single-phase sinusoidal voltage link is presented. System performance is investigated by computer simulation and is verified by test on an actual prototype system. A control loop is proposed for minimizing the link-voltage fluctuation. The capability of rapid demagnetization of the induction machine by current regulation is investigated. A new current modulation technique called switch mode selection is proposed and its performance is compared with the conventional delta modulation technique     

Vector-controlled induction motor drive with a self-commissioningscheme

Different vector-controlled structures are discussed, and their suitability for an economical and reliable industrial drive system is explored. From this, the design of a compact control hardware is derived, composed of an 80196 microcontroller and an ASIC (application-specific integrated circuit) for the generation of the pulsewidth modulation (PWM) signals. The drive system can be configured from a host computer or a hand-held servicing unit through a serial data link. Monitoring and diagnostic functions are included. A self-commissioning scheme permits the setting of the parameters for optimum dynamic performance of the induction motor. Various oscillograms demonstrate the behavior of the vector controller operating a 25-kVA PWM inverter     

A microcomputer-based control and simulation of an advanced IPMsynchronous machine drive system for electric vehicle propulsion

Describes a high-performance microcomputer-based control and digital simulation of an inverter-fed interior permanent magnet (IPM) synchronous machine that uses a neodymium-iron-boron magnet. The fully operational four-quadrant drive system includes a constant-torque region with zero speed operation and a high-speed field-weakening constant-power region. The control uses the vector or field-oriented technique in constant-torque region with the direct axis aligned to the stator flux, whereas the constant-power region control is based on torque angle orientation of the impressed square-wave voltage. All the key feedback signals for the control are estimated with precision. The drive system is basically designed with an outer torque control loop for electric vehicle application, but speed and position control loops can be added for other industrial applications. The distributed microcomputer-based control system is based on Intel-8096 microcontroller and Texas Instruments TMS32010 type digital signal processor     

Online estimation of the stator resistance and leakage inductance of a four-phase induction machine drive

This paper proposes a technique to determine online the stator resistance and the stator leakage inductance of a four-phase induction machine in a four-phase drive system. These parameters are obtained by solving a least squares minimization problem. The technique is conceived to be used online with the drive strategy without disturbing the machine electromagnetic torque. Experimental results are used to demonstrate the feasibility of the proposed technique.     

An improved sensorless vector-control method for an induction motor drive

In the present paper, a new improved sensorless vector-control method for an induction motor drive is presented. The proposed method is based on an improved closed-loop stator-flux estimator, based on the dynamic model of the asynchronous motor, which achieves precise stator-flux estimation over a wide area of operation. This new stator-flux estimator ensures stability of the overall control scheme in a very-wide-speed operation area, as it will be shown in this paper. The rotor-speed-estimation method is based on an observer based on the model reference adaptive systems (MRAS) theory. The control scheme is based on a stator-flux-oriented direct vector-control method, where both flux and speed controllers are optimal tuned. In addition, implementation of the proposed method is based on a simplified algorithm capable of running in a low-cost microcontroller, which is discussed in detail. Also, the motor-drive system, including the stator-flux estimator, the speed estimator, and the control logic are simulated and some characteristic simulation results are presented. These results reveal that the proposed method is able to obtain precise flux and speed control over a wide operation area, including very low operating frequencies.     

A novel rotor resistance identification method for an indirectrotor flux-orientated controlled induction machine system

This paper proposes a novel rotor resistance identification method for an indirect rotor flux-orientated controlled induction machine drive. The method is effectively integrated with the intermediate current control loop of the system. A decoupled synchronous voltage control scheme is used to achieve a fast, accurate current control response and indicates the relative thermal change of the rotor resistance. A model reference adaptive control scheme is then used to track the variation of the rotor resistance. Other issues, such as the nonideal characteristics of the power devices, stator resistance variation and comparison with two other parameter identification methods, are included. This method is less complex and more effective than others, and this is supported by theoretical analysis, and verified by simulation and experimental results     

浅析电力拖动系统的自动控制和安全保护

在我国现代电力系统的发展和建设过程当中,针对电力拖动系统来说,对其进行自动控制以及安全保护,是电力发展过程中的重要研究内容.随着现代科技水平的不断提升,电力拖动系统的自动化控制发展水平逐渐提高,并且在实际的应用中发挥出了重要的价值.本文结合电力拖动系统的控制原理以及实现过程,以鼓风机系统为例进行分析,思考电力拖动系统的...     

An ice machine adapted into an autonomous photovoltaic system without batteries using a variable‐speed drive

The adaptation of a commercially available ice machine for autonomous photovoltaic operation without batteries is presented. In this adaptation a 1040 W_p photovoltaic array directly feeds a variable‐speed drive and a 24 V_dc source. The drive runs an induction motor coupled by belt‐and‐pulley to an open reciprocating compressor, while the dc source supplies a solenoid valve and the control electronics. Motor speed and refrigerant evaporation pressure are set aiming at continuously matching system power demand to photovoltaic power availability. The resulting system is a simple integration of robust, standard, readily available parts. It produces 27 kg of ice in a clear‐sky day and has ice production costs around US$0.30/kg. Although a few machine features might be specific to Brazil, its technical and economical guidelines are applicable elsewhere. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization of a synchronous reluctance machine for a sensorless drive with a wide field-weakening range

For more than one century, electrical machines have been utilized for electrical drives. Nowadays, in most applications the electrical machine is fed by an inverter. Three types of machines are available for such purposes: the asynchronous induction machine, the permanent magnet excited synchronous machine and the synchronous reluctance machine. Reluctance machines represent an alternative to the other types when utilized in high-performance drives with a wide speed range. Due to the rotor saliency, these machines have an inherent suitability for a position-sensorless control. The parameters of a 5 kW machine with a maximum speed of 8000 rpm are evaluated by means of nonlinear finite element analyses. With regard to an application in a high-performance drive with a wide field-weakening range and a position-sensorless control scheme, the characteristics are calculated for the conventional reluctance machine as well as the reluctance machine with additional permanent magnets in the rotor. The comparison of the characteristics of the conventional reluctance machine and the permanent magnet assisted reluctance machine clearly shows the improved performance in terms of electromagnetic torque and power factor due to the interior permanent magnets. Thereby, the suitability for the application in position-sensorless drives due to the high effective saliency is preserved.     

A harmonic elimination and suppression scheme for an open-end winding induction motor drive

In this paper, a harmonic elimination and suppression scheme for a dual-inverter-fed open-end winding induction motor drive is presented. Two isolated dc-link sources with voltage ratio of approximately 1 : 0.366 are required for the present drive. These two isolated do links feeding two inverters to drive the open-end winding induction motor eliminate the triplen harmonic currents from the motor phase. The pulsewidth-modulation scheme proposed enables the cancellation of all the 5th- and 7th-order (6n /spl plusmn/ 1, where n = 1, 3, 5, 7, etc.) harmonic voltages and suppresses the 11th- and 13th-order harmonic voltage amplitudes in the motor phase voltage, in all modulation ranges. The next higher order harmonics present in the motor phase voltages are 23rd, 25th, 35th, 37th etc. (6n /spl plusmn/ 1, n = 4, 6, etc.). By using triangular carrier wave and proper modulating waves for each inverter, the open-end winding induction motor can be operated in the entire modulation range, eliminating all the 6n /spl plusmn/ 1 harmonics (n = 1, 3, 5, 7, etc.) coupled with 11th and 13th harmonic suppression. The proposed scheme also gives a smooth transition to the overmodulation region.     

An implementation of a programmable cascaded low-pass filter for a rotor flux synthesizer for an induction motor drive

This paper investigates a programmable cascaded low pass filter for the estimation of rotor flux of an induction motor, with a view to estimate the rotor time constant of an indirect field orientation controlled induction motor drive. Programmable cascaded low pass filters have been traditionally used in stator flux oriented vector control of the induction motor. This paper extends the use of this filter to estimate the rotor flux for the indirect field orientation control by generating rotor flux estimates from stator flux estimates. This is achieved by using a three-stage programmable cascaded low pass filter. The three-stage programmable cascaded low-pass filter investigated in this paper has resulted in excellent estimation of rotor flux in the steady-state and transient operation of an indirect field oriented drive. The estimated rotor flux data have also been used for the on-line rotor resistance identification with artificial neural network. Modeling and experiment results presented in this paper demonstrate this method of estimating rotor flux clearly.     

A dual two-level inverter scheme with common mode voltage elimination for an induction motor drive

Pulse-width modulated (PWM) inverters are known to generate common mode voltages which cause motor bearing currents in the induction motor drives. They also result in leakage currents which act as sources of conducted electromagnetic interference in the drive system. The common mode voltage generated by a conventional three-level inverter can be eliminated by switching only the voltage space vectors which do not produce the common mode voltage. This paper presents a PWM switching strategy to eliminate common mode voltage using the open-end winding configuration for the induction motor. The switching strategy presented in this paper, does not generate any alternating common mode voltages in the drive system and hence the electrostatic coupling of the common mode voltage, which results in the bearing currents and the leakage currents, is avoided. The proposed scheme is devoid of neutral point voltage fluctuations and does not require neutral point clamping diodes, when compared to the common mode elimination scheme based on the conventional three-level inverter topology. Also, the present scheme uses a single dc-link with half the voltage compared to the conventional three-level inverter based scheme.     

Evaluation of performance criteria of CNC machine tool drive system

The stability, steady-state error analysis, damping factor, and setting time of discrete data drives for computer numerical control (CNC) machine tools are analyzed to obtain the necessary information for the design of a practical system. The stability of the drive is reviewed using Jury's test and the Mitrovic criterion. The variation of damping factor and settling time with respect to system parameters are presented based on the Mitrovic criterion     

Control of low velocity friction and gear backlash in a machine tool feed drive system

Precision-controlled mechanisms are commonly used in machining applications where the feed rates are low, direction reversals are necessary to obtain the desired work piece profile and precision requirements are in the order of micrometers or sub-micrometers. Under these conditions, friction and gear backlash effects contribute significantly to the dynamics of the system. This study investigated the use of neural network models to compensate for these effects. The approach was to switch between two controllers: (i) a proportional-plus-derivative controller together with a feedforward friction compensator when the transmission gears were engaged; and (ii) a feedforward backlash controller when the transmission gears were disengaged. The control scheme was experimentally verified using a retrofitted geared head engine lathe. The results obtained were compared to those obtained with a compensation method found in the literature.     

Sampling-induced resonance in an encoderless vector-controlled induction motor drive

This paper illustrates an effect of sampling in an encoderless vector-controlled induction motor drive with a digital controller. The analysis focuses on the speed observer and the speed control loop which is executed at discrete instants. It is shown that the estimated speed can fluctuate between samples in the speed loop and cause a sustained resonance via feedback. The shaft inertia is not available to smooth the ripple of the estimated speed and the associated resonance could adversely affect the inverter and machine. An analytical model is proposed to evaluate the risk of such a condition in the design and on-site adjustment of control gains. The requirement for a smoothing filter in the speed loop is identified.     

Control and performance of a doubly-fed induction machine intendedfor a flywheel energy storage system

A large-capacity low-speed flywheel energy storage system based on a doubly-fed induction machine basically consists of a wound-rotor induction machine, and a cycloconverter or a voltage-source pulse width modulation (PWM) rectifier-inverter which is used as an AC exciter. Adjusting the rotor speed makes the machine either release the kinetic energy to the power system or absorb it from the utility grid. Thus, the machine has the capability of achieving not only reactive-power control, but also active-power control based on the flywheel effect of the rotating parts. This paper proposes a new control strategy for a doubly-fed induction machine intended as a flywheel energy storage system, which is characterized by the combination of vector control and decoupling control. The control strategy enables the induction machine to perform active-power control independent of reactive-power control even in transient states. The validity of the theory developed in this paper, along with the effectiveness and viability of the control strategy, is confirmed by computer simulation. In addition, this paper discusses a transient behavior of a magnetizing current in the induction machine     

A novel DC chopper drive for a single-phase induction motor

The paper presents a new drive for single-phase induction motors. This drive employs a DC chopper circuit with a diode bridge rectifier connected with the stator in a nonconventional fashion. The speed of the single-phase induction motor is controlled by controlling the chopping frequency of the chopper switch. The attractive feature of the drive is that it effects both frequency and phase-angle control simultaneously. The drive performance has received both theoretical and experimental investigation     

Development of a protection system for an experimental SMES device

The development and testing of a quench detection and protection system for a small, liquid helium cooled, superconducting coil are described. The coil is being used as part of an experimental superconducting magnetic energy storage (SMES) device for power system applications. Special requirements are placed on the detection and protection system of such a coil as rapid energy exchanges are frequent. The detection signal is derived from a combination of the main coil voltage and a search coil voltage. The protection method is by way of an external parallel resistor. The problem of opening a circuit breaker in series with the coil is analyzed. Actual quench recordings are used to demonstrate the effectiveness of the system. The selection of the dump resistor value is considered