Showing papers in "Ieej Transactions on Industry Applications in 1992"
19 citations
TL;DR: The details of control characteristics of the NPC inverter are described and a new PWM control to cover the whole operating ranges are proposed and the digital simulations and the experimental results are described to clear the effects of new control methods.
Abstract: Pulse width modulated inverters using GTOs are aptly used high quality AC motor drives. A nuetral point clamped (NPC) inverter with three level output voltage is of great advantages to large capacity AC motor drives: lower ripple currents and higher output voltages.GTOs in inverters call for the minimum on-time to discharge the capacitive energy of snubber circuits. The NPC inverter cannot control the pulse-wise voltage for a small reference on account of the minimum on-time.This paper describes the details of control characteristics of the NPC inverter and proposes a new PWM control to cover the whole operating ranges. The digital simulations and the experimental results are described to clear the effects of new control methods.Finally, the NPC inverter is compared with the conventional bridge inverter at the point of applying to AC moter drives.
19 citations
TL;DR: In this article, the authors report the method of electric power generation from tidal currents and test results of the system which was specially designed for this purpose, consisting of a vertical axis turbine, a accelerator, an electric generator, and a control unit.
Abstract: This paper reports the method of electric power generation from tidal currents and test results of the system which is specially designed for this purpose. The system consists of a vertical axis turbine, a accelerator, an electric generator, and a control unit. The turbine is vertical axis Darrieus rotor, and has three blades. The real test in tidal currents was conducted from 1983 to 1988, at Kurushima straits, and its results are discussed.
18 citations
17 citations
TL;DR: In this article, a flux-weakening technique is applied to the air-gap flux of a PM motor to reduce the field current as the speed increases, which results in constant power and wide speed range operation.
Abstract: Permanent magnet synchronous (PM) motors are widely used for industrial applications. In traction and spindle drives, the constant power operation and wide speed range are desirable. With DC motor drives, these are achieved by the appropriate reduction of the field current as the speed increases. In the PM motor, the direct control of magnet flux is not available. The air-gap flux, however, can be weakened by the direct axis armature reaction. This control technique is called “flux-weakening” instead of “field-weakening”. This paper describes a variable speed drive system of PM motor for the constant power and wide speed range operations. In the proposed control system, a novel flux-weakening technique is applied. The current vector is controlled so that the maximum torque per armature current can be obtained at low speeds and the terminal voltage is kept within its limited value at high speeds. The control performances are examined by the simulations and the experimental results.
16 citations
TL;DR: In this article, a low cost and high power active filter for a DC transmission system is proposed, where the voltage of the inverter is controlled to cancel the voltage drop of the internal resistance of the filter.
Abstract: Usually, to eliminate the harmonics of transmission lines, LC tuned filters are employed to let bypass these harmonic components. But the elimination ability is limited by its damping resistance. Therefore, active filters composed of high frequency PWM converters are desirable. Comparing with the LC tuned filters, the cost would be very high even in high power systems.In this paper, a low cost and high power active filters for a DC transmission system is proposed. It has active filter ability as well as low cost for high power uses. Its main circuit is composed of conventional LC filters in series with square wave voltage inverters. The voltage of the inverter is controlled to cancel the voltage drop of the internal resistance of the LC filter. So the Q factor of the filter can appear infinity. Calculation of the harmonic and the control are done by DSP (TMS 32010). In the experimental system and simulations, two three phase tuned filter 5-th and 7-th are employed. Excellent results under 1% distortion voltage are obtained.
13 citations
TL;DR: In this article, a ripple compensation circuit with a small auxiliary capacitor controlled by a 2-quadrant chopper connected in parallel to the smoothing capacitor is presented, which absorbs the ripple energy efficiently.
Abstract: The single-phase converter or rectifier always has a voltage ripple in the output DC voltage, because the instantaneous power of the single-phase AC line varies on the double frequency of the line. In order to obtain a smooth DC voltage, an energy storing element is necessary. The smoothing capacitor is used to reduce the ripple voltage in the DC output. Usually, it has much larger capacitance than that needed to absorb the ripple energy. This paper discusses the required capacitance to absorb the ripple energy, and represents a ripple compensation circuit with a small auxiliary capacitor controlled by a 2-quadrant chopper connected in parallel to the smoothing capacitor. The appended capacitor works under large ripple voltage and efficiently absorbs the ripple energy. The ripple compensation curcuit works as an equivalent capacitor which has a large capacitance.
12 citations
TL;DR: In this article, the authors investigate the possibilities of Pmax control using the output power, the output voltage and the output current instead of the solar cell output power and examine about the optimal power converter using step up and down chopper circuit to operate the solar cells at an optimal voltage using these variables.
Abstract: As well known, a solar cell has an optimal operating point to be able to get the maximum power Pmax. But it may vary depending on the miss match between the solar cell output and the load. So, many Pmax tracking controllers using microprocessor have been popularly used. In the conventional control system, the solar cell output power is used as a control variable.In this paper, we investigate the possibilities of Pmax control using the output power, the output voltage and the output current instead of the solar cell output power. And we also examine about the optimal power converter using step up and down chopper circuit to operate the solar cell at an optimal voltage using these variables. And then, we show some experimental results to confirm the successful operation.From the investigations, we may be concluded that the control variables using the output voltage and the output current is useful and for general applications connecting to the DC load composed of the resistive load and the voltage source, the output current control is better than the others.
12 citations
TL;DR: In this article, a new approach focusing on the fact that this kind of disturbance constitutes cyclic function of the rotational angle was proposed, which is set in the "angle domain" instead of the "time domain" so as to eliminate such disturbances completely without regard to the rotation speed.
Abstract: High precision and good command response are the most important requirements in performance of constant speed rotation control systems. It is the rotational speed fluctuations caused frequent by rotational angle dependent disturbances that have hindered all efforts to improve the precision of such systems.This paper proposes a new approach focusing on the fact that this kind of disturbance constitutes cyclic function of the rotational angle. The proposed design is set in the ‘angle domain’ instead of the ‘time domain’ so as to eliminate such disturbances completely without regard to the rotational speed.The results of the simulation reported in this paper will prove that the constant speed rotation control system designed according to the proposed approach removes all rotational speed fluctuations apart from speed setting changes.
12 citations
12 citations
TL;DR: In this paper, an analysis of the original brushless synchronous generator without exciter is presented, where the output voltage can be adjusted in a wide range by controlling the stator dc current.
Abstract: Recently, a demand for small-capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines.
It is desired that the structure of small-capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled.
This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.
TL;DR: In this paper, an 8-shape levitation coils arranged on the vertical surface of the guideway were examined using numerical examples and experimental data, and the results showed stable running and balanced displacement which agreed with calculated values.
Abstract: A levitation method has been introduced which uses 8-shape levitation coils arranged on the vertical surface of the guideway. These coils can act as a guidance means as well as the levitation means. The characteristics of this system are examined using numerical examples and experimental data. The cables connecting right and left coils are not connected to a high-voltage power source unlike the usual guidance system which is combined with propulsion. Thus the electric insulation of the cables is not a problem at present. Numerical examples show that the levitation characteristics of the combined levitation and guidance system are almost the same as in the system without the guidance function, and that it attains reduced running resistance with necessary guidance stiffness obtained. A test run was done at Miyazaki Test Line equipped with coils of this type arranged about 120 m, and the results show stable running and balanced displacement which agrees with calculated values.
TL;DR: In this article, the authors proposed a fully digital current control method with DSP for the vector control of the induction motor, which makes the delay between the PWM signal and the actual output voltage constant.
Abstract: This paper proposes a fully digital current control method with DSP for the vector control of the induction motor.First, we present a new dead time compensation circuit, whch makes the delay time between the PWM signal and the actual output voltage constant. Therefore, the synchronous current sampling with the PWM signal can detect the accurate fundamental frequency component from the ripply current.Moreover, we discuss the current regulator which improves the response of the primary current and compensates the parameters deviation of the motor. And, we show that this control system is possible to get the quick response and the low current ripple in spite of the slow sampling rate by the experimental results.
TL;DR: In this article, the authors proposed a new method which predicts the frequency response of a synchronous motor by using values of DC decay test in the armature winding at standstill, which can predict easily and exactly a low frequency response below one Hz.
Abstract: It is almost impossible to measure the starting performance of middle and large synchronous motors in a factory, because it needs a large capacity of equipments to test their performance.A new method is required to predict their performance by simple tests using a small capacity. This will make the motor's design and accessories more rationalized.Authors propose a new method which predicts the frequency response by using values of DC decay test in the armature winding at standstill.The key points of this method are summarized as follows:(1) DC voltage is applied to the armature winding (two terminals with the third one open) of a synchronous motor through a resistance. When two terminals are closed, the winding is shortcircuited and the current in the armature winding decays. The whole process of current decay is recorded. The impedance on motor terminals per phase are decided by Fourier transformation of the current decay.(2) This new method is quite useful. It is possible to predict easily and exactly a low frequency response below one Hz.The starting performance of a synchronous motor is predicted and agrees with actual data.
TL;DR: This work proposes the novel estimation technique of the instantaneous speed by utilizing the armature current together with the encoder information, and implements it by using a DSP, and proves that it can greatly improve the system stability and achieves the excellent disturbance rejection performance.
Abstract: We propose the instantaneous speed observer for high performance control of servomotors which use inexpensive low precision shaft encoders. Due to the recent development of DSP (Digital Signal Processors), we have been able to control servomotors with a very short sampling period. We usually obtain the speed information from the increased pulse number of a shaft encoder in a sampling period. However, in this simple method, we lose the speed resolution easily. If we get accurate speed information by clocking the period of encoder pulse, the system will be easily unstable in the lower speed range because a long deadtime is inserted in the feedback loop. To overcome these problems, we propose the novel estimation technique of the instantaneous speed by utilizing the armature current together with the encoder information. As this observer inherently includes the disturbance observer. We can use it for the effective disturbance rejection control. We implement this system by using a DSP, and prove through laboratory experiments that it can greatly improve the system stability and achieves the excellent disturbance rejection performance.
TL;DR: In this paper, a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command is presented. But the method is not suitable for field-oriented induction motor drive.
Abstract: Several field oriented induction motor drive methods without rotational transducers have been proposed. These methods have a disadvantage that the rotor resistance variation causes the estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper presents a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command. >
TL;DR: In this article, a current control loop is composed of the γ-δ axes in which the ρ axis is coincident to the stator current, and an initial tuning of the equivalent mutual inductance is achieved by detecting the deviation component of the stators voltage on the δ axis at the no load running condition.
Abstract: In the vector control system using the slip frepuency control method, the rotor resistance of an induction motor is used for calculating a slip frequency. So that the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of the compensation for the rotor resistance change which is robust for the stator resistance change. A Current control loop is composed of the γ-δ axes in which the γ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved particularly in the low speed region. The experimental results of the current response and the compensation for the rotor resistance deviation were shown, too.Moreover though the mutual inductance has been treated as an invariable value, the value does change by a frequency and an excitine command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no load running condition. Furthermore in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance were shown.
TL;DR: In this article, the frequency of the harmonic fluxes, which are the main factor of vibration and noise, is discussed, and the modes and frequencies of electromagnetic radial force wave induced by these harmonics are calculated.
Abstract: The small squirrel cage three-phase induction motor has been used in all types of industry for a number of years. Motor radial vibration and noise caused by electromagnetic force are addressed in this paper.At first, the frequency of the harmonic fluxes, which are main factor of vibration and noise, is discussed. Then modes and frequencies of electromagnetic radial force wave, induced by these harmonic fluxes, were calculated.Natural frequency responses and modes of experimental motors were measured. Also frequencies and modes of vibration were measured on a running experimental motor. The experimental data was compared with the calculated values.As a result, it was newly confirmed that modes of the running motor were determined to be a function of the natural frequency mode of the structure, not by modes of the electromagnetic radial force wave. It became clear that these modes did not rotate around the core. They were stationary waves.
TL;DR: In this paper, the flux estimator is interpreted as a flux observer, and then a linear model of the system is proposed by deriving the equations of the flux estimation in a synchronously rotating reference frame.
Abstract: One of the representative vector-controlled induction motor drive system without a speed sensor is composed of a rotor flux estimator, a PI torque current controller and a conventional vectorcontrolled current source. However, the stability analysis of this system has not appeared in the literature.In this paper, the flux estimator is interpreted as a flux observer, and then a linear model of the system is proposed by deriving the equations of the flux estimator in a synchronously rotating reference frame. By computing the trajectories of the poles and zeros and the transient responses, the following results are obtained.(1) If the rotor flux is estimated using only the stator equations (voltage model), the system becomes unstable when the actual stator resistance is smaller than the value used by the controller.(2) By choosing a small time constant of the first order lag element in the flux estimator (reciprocal number of observer gain), the poles and zeros on the imaginary axis move to the stable region. However, another pair of poles has reverse performance.(3) From the viewpoint of stability, the gain of the PI torque current controller should be chosen as large as possible and the stator and rotor resistances in the controller should be set to smaller values than their actual values.
TL;DR: In this article, a method of determining parameters of PWM rectifiers based on the degrees of total harmonic distortion (THD) was proposed, which enables us to calculate approximate THD values without conducting any simulations or experiments.
Abstract: This paper describes a method of determining parameters of PWM rectifiers based on the degrees of total harmonic distortion (THD). The inductance value of AC reactors and capacitance value of DC capacitor give a great influence on the amplitude of the harmonics in the AC input currents and DC output voltage, respectively. So far simulation-based harmonic analysis is dominant. In this paper we propose the harmonic distortion determining factor that provides a simpler and broader manner of obtaining THD values, that is, it enables us to calculate approximate THD values without conducting any simulations or experiments. Finally experiment using a DSP is carried out to confirm the usefulness. An optimal regulator theory is applied to the controller design.
TL;DR: In this paper, the disturbance observer is applied to each joint to improve the robustness against the disturbance effect and the joint acceleration controller is realized in the joint space, where the workspace motion equation is derived and the workspace force controller is constructed based on its motion equation.
Abstract: The paper describes a workspace force controller of the multi-degrees-of-freedom manipulator. First, the disturbance observer is applied to each joint to improve the robustness against the disturbance effect and the joint acceleration controller is realized in the joint space. Secondly, the workspace motion equation is derived and the workspace force controller is constructed based on its motion equation.In the proposed force controller, the equivalent mass matrix of the workspace is defined clearly and the impedance of the manipulator is selected arbitrary. This is a remarkable point of the proposed method. Several experimental results are shown to verify the proposed controller.
TL;DR: In this paper, the authors proposed a real-time control algorithm for a series-resonant high-frequency linked converter with a DC input and a single-phase sinusoidal AC voltage output.
Abstract: This paper proposes a open-loop and real-time control method of a series-resonant high-frequency linked converter with a DC input and a single-phase sinusoidal AC voltage output.Resonant converters have lately attracted considerable attention because they can perform zero-current or zero-voltage switching, which produces little switching loss, and high frequency operation which realize compact converters. The conventional resonant converters are mainly DC-to-DC converters and DC-to-AC ones, and their control algorithms are based on the transient operations from microscopic viewpoint. Therefore, the macroscopic transient characteristics of the converters including their load has not been studied sufficiently from macroscopic viewpoint. Moreover, the conventional control algorithms of DC-to-AC converters require detection of the voltage or current in the resonant circuit or the switching devices to realize stable resonant operation and zero-current or zero-voltage switching.In this peper, an approximate analysis of the basic series-resonant converter is performed, and then simple equations and an equivalent circuit of the converter are obtained by introducing some rules to the switching sequences of the converter. Based on the equations and the equivalent circuit, a realtime and openloop control algorithm of the series-resonant converter is derived in the same way as the conventional PWM inverters/converters to obtain a single-phase sinusoidal and rectangular voltage waveform.Experimental results to confirm the feasibility and the usefulness of the proposed control algorithm are presented.
TL;DR: In this article, the PWM cycloconverter was used to control flow of power bidirectionally, and charge the DC power supply and compensate instantaneous reactive power in a high frequency link DC/AC converter with three phase output voltages.
Abstract: High frequency link DC/AC converters for UPS are characterized by small size and weight of the isolation transformers. Two types are considered in the high frequency link DC/AC converters. One is called a DC/DC converter type, and the other is a cycloconverter type. The DC/DC converter type can be constructed easily, but the efficiency is low because of many steps of power conversion The system configuration for the cycloconverter type with a single phase output has been proposed, but the cycloconverter type which directly converts high frequency voltage into three phase line voltages is not studied.In this paper, the system configuration and the control method of the high frequency link DC/AC converter with three-phase output voltages using the PWM cycloconverter are proposed. This system can control flow of power bidirectionally, and charge the DC power supply and compensate instantaneous reactive power. Simulations and experiments are carried out to confirm the feasibility of the proposed system.
TL;DR: In this paper, the load current of converter is detected without delay time and ripple by multiplying the output currents or motor currents and the inverter PWM signals and the very simple control method is proposed.
Abstract: Rectifiers composed of diodes or thyristors have many harmonics in line currents. Recently, PWM converters have been actively studied to reduce the harmonics. In order to put them into practical use, not only PWM control method but also the following control methods must be established.(1) Method for reducing the capacity of dc link capacitor.(2) Restarting method from instantaneous power interruption.For reducing the capacity of do link capacitor, it is necessary to suppress the fluctuation of dc link voltage at a sudden change of load. In this paper, the load is inverter for variable speed induction motor drives. The load current of converter, that is the inverter input current, is detected without delay time and ripple by multiplying the inverter output currents or motor currents and the inverter PWM signals. By adding the detected signal to do link voltage control loop as a compensating component, the fluctuation of dc link voltage at a sudden load change can be suppressed. As a result, the capacity of the dc link capacitor or can be reduced to smaller than one-fifth of that in the conventional diode rectifier. For restarting from instantaneous power interruption, the very simple control method is proposed. When the dc link voltage becomes low limitation value setted at a little bit lower than that obtained in diode rectifier in the period of power interruption, the PWM signals to converter are blocked. After recovery from power interruption, when the dc link voltage reaches the low limitation value, the PWM control signals are supplied to the converter again and it is restarted the operation. From the experimental results, it was confirmed that the PWM converter can be restarted from the instantaneous power interruption very smoothly.
TL;DR: In this article, an on-line FMS scheduling system, which takes in consideration the routing flexibility is proposed, where the FMS is modeled utilizing a Timed Petri net representation, which provides real time information about the production evolvement and the status of each machine and equipment.
Abstract: An on-line FMS scheduling system, which takes in consideration the routing flexibility is proposed in this paper. The FMS is modeled utilizing a Timed Petri net representation. This representation provides real time information about the production evolvement and the status of each machine and equipment. With this information the proposed system starts to search for the scheduling of the next orders to be assigned. The search is performed by a beam search based on-line decision method. The developed algorithm, integrating the Timed Petri net representation to the beam search, is described. To test the developed system Just-in-Time production objective was established. The performance of the system is evaluated through exhaustive simulations. The achieved results are very promising, as the proposed system leads not only to a better achievement of the production objective, but also to smaller variance under different scheduling conditions, suggesting greater reliability.
TL;DR: In this article, the dynamic and static characteristics of an attractive type magnetic levitation system with 3φ AC electro-magnets are analyzed and a transfer function of the system is given.
Abstract: This paper is investigating characteristics of an attractive type magnetic levitation system with 3φ AC electro-magnets. The system has iron rails with primary windings on the ground and levitation magnets with secondary windings placed on the levitated object, and the object is levitated by feed-back control of magnetically induced current of the levitation magnet. In this system, the levitated object has no part contacting the ground and needs no on-board battery.In the paper, dynamic and static characteristics of the AC levitation system with 3φ AC magnets are analyzed and a transfer function of the system is given. The transfer function is determined by the magnet constants which can measured by using the method to measure constants of a transformer. The dependency of the system characteristics and stability on the magnet and the feed-back constants are discussed based on the analysis. To investigate the validity of the analysis, an experiment has been performed by making a one-point support model system. Experimental results well agreed with the analytical results considering that the system is non-linear and has AC coupling circuit, and we consider that the analysis described in the paper is valid.