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Journal ArticleDOI

Load-Commutated Inverter/Synchronous Motor Drive Without a Shaft Position Sensor

01 Jan 1979-IEEE Transactions on Industry Applications (IEEE)-Vol. 1, Iss: 1, pp 63-71
TL;DR: In this article, a load-commutated inverter consisting of two bridges connected in parallel is used to provide two-way power flow by reversing the dc current. But the control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor internal operating conditions.
Abstract: Synchronous motor drives are beginning to enjoy renewed popularity for certain applications such as flywheel energy storage. One of the reasons is that a synchronous motor drive can be made self-commutating so that the inverter becomes equivalent to a conventional phase-control bridge converter without large commutating components. The drive to be controlled consists of an inductor alternator coupled to a flywheel that will be used for temporary energy storage. The flywheel speed will vary over a two-to-one range; thus full performance can be achieved using a load-commutated inverter. A simple auxiliary commutating circuit is provided only for initial starting. The drive must operate both from a fixed dc voltage source (battery) and from a variable dc voltage source (dc motor), as it is intended for use in a battery-powered vehicle for load leveling. The load-Commutated inverter consists of two bridges connected in parallel so as to provide two-way power flow by reversing the dc current. The control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor Nare internal operating conditions. This control method maintains the silicon-controlled rectifier (SCR) turn-off time as a constant percentage of the period of the generated back electromotive force (EMF) as speed and current are varied during operation. The inverter turn-off time is thus maintained by feedback control rather than the use of special function generators. A 20-kVA laboratory development drive system has been built and successfully tested using this control strategy.
Citations
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Journal ArticleDOI
Kenichi Iizuka1, Hideo Uzuhashi1, Minoru Kano1, Tsunehiro Endo1, Katsuo Mohri1 
TL;DR: In this article, the motor voltage is chopped by commutator transistors to change the motor speed, and the motor rotor position is determined by the back electromotive force induced in the stator windings.
Abstract: The microcomputer control of a brushless motor without a shaft position sensor is studied. A method which permits the determination of the permanent magnet rotor position by the back electromotive force (EMF) induced in the stator windings and the starting technique which uses the motor as a synchronous motor at standstill are explained. The motor voltage is chopped by commutator transistors to change the motor speed. The control system consists of a 4-b single-chip microcomputer and two quad-comparators.

455 citations

Proceedings ArticleDOI
02 Oct 1994
TL;DR: In this paper, a position sensorless control scheme for a doubly excited induction machine is proposed, which uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability.
Abstract: A novel control strategy to realize decoupled control of torque and reactive power for a doubly excited induction machine using a position sensorless scheme is proposed. The critical issues related to the torque angle estimation and control for a doubly excited induction machine are discussed. Compared to the other position sensorless schemes for a doubly fed machine, the proposed control method uses only the rotor voltages and currents as the feedback signals, which substantially reduces the costs and enhances the reliability of the position sensorless control of a doubly fed AC machine. Computer simulation and experimental results are given to verify the position sensorless control scheme. >

317 citations

Journal ArticleDOI
02 Oct 1994
TL;DR: In this paper, an indirect sensing method for rotor flux position for brushless permanent magnet (BPM) motors operating over a wide speed range, while keeping maximum torque per ampere and/or maximum efficiency capabilities, is described.
Abstract: This paper describes an indirect sensing, or sensorless, method for rotor flux position for brushless permanent magnet (BPM) motors operating over a wide speed range, while keeping maximum torque per ampere and/or maximum efficiency capabilities. The method described is particularly applicable to trapezoidal back emf type of BPM motors. The typical trapezoidal waveform of the motor internal voltages (or back emf) contains a fundamental and higher order frequency harmonics. In particular, the third harmonic component is extracted from the stator phase voltages while the fundamental and other polyphase components are eliminated via a simple summation of the three phase voltages. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition, and is practically free of noise that can be introduced by the inverter switching, making this a robust sensing method. In contrast with indirect sensing methods based on detection of the back-emf signal that require heavy filtering, the third harmonic signal needs only a small amount of filtering to eliminate the switching frequency and its side bands. As a result, the method described here is not sensitive to filtering delays, allowing the motor to achieve a good performance over a wide speed range. Motor starting is also superior with this method since the third harmonic signal can be detected and processed at lower speeds than for the conventional method of back-emf sensing.

218 citations

Journal ArticleDOI
TL;DR: In this article, a neutral point diode clamped (NPC) converter system was proposed for high capacity wind power units in large wind farms, which accommodates higher voltage and power ratings of a high-capacity wind power unit.
Abstract: Recent and ongoing developments in wind turbine technology indicate a trend towards utilization of high capacity (e.g., up to 5 MW) wind power units in large wind farms. Higher capacity of the wind turbine necessitates operation of the corresponding electric machine and the static converter system at higher voltages. This paper presents a neutral point diode clamped (NPC) converter system that inherently accommodates higher voltage and power ratings of a high capacity wind power unit. The overall control strategy of an NPC-based wind power unit and the details of the ac side and the dc side controls of the NPC converter system are also described. The generator-side NPC converter provides torque-speed control of the turbine-generator unit. The network-side NPC converter controls real and reactive power flow to the network and thus regulates the dc bus voltage and the ac side power-factor (or voltage) respectively. The paper also presents a new control approach to balance the dc capacitor voltages. The NPC converter system is augmented with a dc chopper that controls the synchronous generator field current. The NPC-based converter system is used to interface a 3 MW, direct-drive (gearless), synchronous machine based wind power unit to the utility grid. Performance of the overall NPC-based wind power unit, under the proposed controls, is evaluated based on time domain simulations in the power systems computer aided design (PSCAD) electromagnetic transient for DC (EMTDC) environment.

185 citations


Cites methods from "Load-Commutated Inverter/Synchronou..."

  • ...The structures of the machine current regulators, based on the availability of the rotor angle θr and speed ωr via either measurement or estimation [13], is as follows:...

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Journal ArticleDOI
Bimal K. Bose1
01 Feb 1982
TL;DR: In this paper, the authors reviewed the present status of ac drives technology in which the salient technical features of ac machines, converters, controls, and performances of the integrated drive systems have been discussed, and the appropriate trend of the technology has been indicated.
Abstract: The technology of solid-state adjustable speed ac drives was launched in the 1960's. Since then many innovations in devices, circuits, control theory, and signal electronics have made a considerable contribution to this technology. With the heritage of past experience, and the projection of present trends, an almost certain prediction can be made that adjustable speed ac drives will find widespread applications in industry before the end of this decade. The paper reviews the present status of ac drives technology in which the salient technical features of ac machines, converters, controls, and performances of the integrated drive systems have been discussed, and wherever possible, the appropriate trend of the technology has been indicated.

103 citations

References
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Journal ArticleDOI
TL;DR: In this article, the analysis presented in a previous paper is extended to include a consideration of synchronizing and damping torque during continuous and transient oscillations, the description of an equivalent circuit which has been found useful in calculating the decrement of the short circuit current of interconnected machines, and the derivation of simple approximate formulas for the roots of the equation determining the wave shape of the current on three-phase short circuit.
Abstract: The analysis presented in a previous paper is extended to include a consideration of synchronizing and damping torque during continuous and transient oscillations, the description of an equivalent circuit which has been found useful in calculating the decrement of the short circuit current of interconnected machines, and the derivation of simple approximate formulas for the roots of the equation determining the wave shape of the current on three-phase short circuit.

320 citations

Journal ArticleDOI
TL;DR: An extension of the 2-reaction theory of synchronous machines as developed by R. H. Park is given in this paper for machines having capacitance in the armature circuit.
Abstract: An extension of the 2-reaction theory of synchronous machines as developed by R. H. Park is given in this paper for machines having capacitance in the armature circuit. General equations for predetermination of the performance under certain abnormal conditions of machines having balanced 3-phase capacitance in the aramture circuit are presented.

79 citations

Journal ArticleDOI
TL;DR: In this paper, a synchronous control of an induction motor is presented, which achieves the necessary system stabilization by controlling only the motor frequency, by adjusting the phase of the converter firing signals.
Abstract: Conventional methods of controlling an induction motor utilize regulation of stator current and motor slip frequency in order to maintain system stability. This control strategy requires a shaft speed feedback and fast-response current regulation. An alternative method of controlling an induction motor is presented which achieves the necessary system stabilization by controlling only the motor frequency. The control inherently regulates the motor torque angle by properly adjusting the phase of the converter firing signals. By synchronizing the inverter firing pulses to the motor back electromotive force (EMF) possible adverse inverter operating modes are avoided. The concept of synchronous control eliminates the preprogrammed functional relations previously required and allows the control to adapt to any desired motor flux level. Any desired outer regulating loop can be incorporated to form a fast-response wide-range ac drive system.

46 citations

Journal ArticleDOI
TL;DR: In this article, a load-commutated inverter synchronous motor drive system employing a simple auxiliary commutation circuit for machine startup is analyzed, and results hybrid computer simulation are presented.
Abstract: A load-commutated inverter synchronous motor drive system employing a simple auxiliary commutation circuit for machine startup analyzed, and results hybrid computer simulation are presented. The commutation circuit employs a single commutation capacitor connected to the neutral of the machine and two auxiliary thyristors, which are used only during machine starting. A practical operating scheme is developed for the forced commutated inverter, which insures commutation over all load currents by actively allowing the commutation capacitor to charge to a voltage proportional to load, current. Results of key computer runs are given including inverter waveforms, transient waveforms during transition from forced to load commutation, as well as the effect of forced commutation and load commutation on pulsating torque. The forced-commutation circuit is used only for synchronous machine startup. However, due to its simplicity it also is an attractive alternative to be considered for other types of current-fed inverter ac drives.

45 citations