Showing papers on "Inverter published in 1988"

Direct self-control (DSC) of inverter-fed induction machine

Abstract: The new direct self-control (DSC) is a simple method of signal processing that gives converter-fed three-phase machines an excellent dynamic performance. To control the torque of, say, an induction motor, it is sufficient to process the measured signals of the stator currents and the total flux linkages only. In the basic version of DSC, the power semiconductors of a three-phase voltage source inverter are directly switched on and off via three Schmitt triggers, comparing the time integrals of line-to-line voltages to a reference value of desired flux, if the torque has not yet reached an upper-limit value of a two-limit torque control. Optimal performance of drive systems is accomplished in steady state as well as under transient conditions by combination of several two-limit controls. >

Programmed PWM techniques to eliminate harmonics - A critical evaluation

Abstract: Programmed pulsewidth modulators (PWMs) eliminating several lower-order harmonics generate high-quality output spectra, which in turn result in minimum current ripple and reduced torque pulsations, thereby satisfying several performance criteria and contributing to overall improved performance. Several programmed PWM switching patterns to eliminate harmonics in the output spectra of single-phase and three-phase inverters are possible. Each of these leads to a specific advantage in single- and three-phase inverters, depending on the application. First, the superiority of programmed PWM techniques over the conventional carrier-modulated PWMs is established. Next, a critical evaluation of the programmed PWM schemes on the basis of applications for single- and three-phase inverters is used to provide a framework and guidelines for the selection of the appropriate technique for each application area. Evaluation criteria include harmonic loss factor and total harmonic distortion factors defined at the input and output of the inverter terminals. Finally, a simple low-cost solution for obtaining the required PWM switching points is proposed. Selected results are verified experimentally. >

Deadbeat controlled PWM inverter with parameter estimation using only voltage sensor

Abstract: A technique based on deadbeat control theory is proposed to obtain a nearly sinusoidal PWM (pulsewidth-modulated) inverter output voltage using only a voltage sensor. The closed loop sampled-data feedback scheme inherently results in very fast response to load disturbance and nonlinear load, producing low total harmonic distortion. Parameter estimation of the plant provides a type of self-tuning of the proposed controller. A theoretical analysis, simulation, and experimental results are presented for a single-phase PWM inverter controlled by an Intel 8086 microprocessor. >

A high-performance inverter-fed drive system of an interior permanent magnet synchronous machine

Abstract: A high-performance, fully operational four-quadrant control scheme for the interior permanent magnet (PM) synchronous machine is described. The machine operates smoothly with full performance in the constant-torque region as well as in the flux-weakening constant-power region in both directions of motion. The transition between the constant-torque region and the constant-power region is very smooth at all conditions of operation. Control in the constant-torque region is based on the vector stator flux, while constant-power region control is implemented through the feedforward vector rotator. The control system is digitally implemented using a distributed microcomputer system, and all of the essential feedback signals such as torque, flux, etc. are estimated with precision. A 70 hp drive system using a neodymium-iron-boron (NeFeB) PM machine and transistor pulse width modulation inverter was designed and extensively tested in the laboratory on a dynamometer, and performance was found to be excellent. >

Waveform compensation of PWM inverter with cyclic fluctuating loads

Abstract: A repetitive voltage compensation technique that generates a high-quality sinusoidal output voltage from a single-phase pulse width modulation (PWM) inverter used for uninterruptible power supplies is described. A repetitive control technique eliminates the steady-state error in the distorted output voltage caused by cyclic loads. The proposed PWM inverter system uses microprocessor-based closed-loop digital feedback with a sinusoidal reference. The PWM pattern is determined at every sampling instant by the proposed algorithm, implemented by a microprocessor using a set of detected output voltages and the reference signals through one cycle. The system has low distortion and very fast response for AC phase-controlled loads. >

An Adaptive Hysteresis-Band Current Control Technique of a Voltage-Fed Pwm Inverter for Machine Drive System

Abstract: An adaptive hysteresis-band control method where the band is modulated with the system parameters to maintain the modulation frequency to be nearly constant is described Although the technique is applicable to general AC motor drives and other types of load, an interior permanent magnet (IPM) synchronous machine load is considered Systematic analytical expressions of the hysteresis band are derived as functions of system parameters An IPM machine drive system with a voltage-fed current-controlled PWM (pulse width modulation) inverter has been computer simulated to study the performance of the proposed method >

High performance CMOS surrounding gate transistor (SGT) for ultra high density LSIs

Abstract: A novel transistor with compact structure has been developed for MOS devices This transistor, whose gate electrode surrounds the pillar silicon island, reduces the occupied area for all kinds of circuits For example, the occupied area of a CMOS inverter can be shrunk to 50% of that using planar transistors The other advantages are steep cutoff characteristics, very small substrate bias effects, and high reliability These features are due to the unique structure, which results in greater gate controllability and in electric field relaxation at the drain edge >

Fully digital, vector-controlled PWM VSI-fed AC drives with an inverter dead-time compensation strategy

Abstract: A dead-time compensation method in vector-controlled pulse width modulator (PWM) voltage source inverters (VSIs) is proposed. The method is based on a feedforward approach that produces compensating signals obtained from the I/sub d/-I/sub q/ current and inverter output angular frequency references in the rotating reference (d-q) frame. It provides excellent inverter output voltage distortion correction for both fundamental and harmonic components. The correction is not affected by the magnitude of the inverter output voltage or current distortions. Since this dead-time compensation method allows current loop calculations in the d-q frame at a slower sampling rate, with a conventional microprocessor than calculations in the stationary reference frame, a fully digital. vector-controlled speed regulator with just a component current control loop is realized for PWM VSIs. Simulations and test results obtained for the compensation method are also described. >

Design methodologies for soft switched inverters

Abstract: A detailed design methodology is presented for soft switched inverters. The actively clamped resonant DC link inverter and the resonant pole inverter are taken as illustrative design examples with a detailed enumeration of component design rules, switching loss calculations, and system optimization. The soft-switched circuits are then compared with the conventional hard-switched voltage-sourced inverter under identical load conditions. >

An efficiency-optimizing permanent-magnet synchronous motor drive

Abstract: A permanent magnet synchronous-motor drive that uses and adaptive control to find the maximum-efficiency operating point at any speed and load is demonstrated. Active damping is provided by modulating the inverter frequency in proportion to the perturbations in the average inverter DC link current. All principal control functions, including efficiency optimization and frequency modulation, are performed by a real-time digital control algorithm, using only the filtered inverter DC link current as a feedback signal from the inverter. Laboratory tests and computer simulations demonstrate the performance of the efficiency-optimizing control and the frequency-modulation feedback loop. >

Analysis and design of a three-phase offline DC-DC converter with high-frequency isolation

Abstract: Single-phase offline switch mode rectifiers (or offline DC-DC converters) face severe component stresses in higher than 10kW applications. The authors show that in three-phase, switch-mode rectifier (SMR) topologies' component stresses are reduced, and performance is improved substantially. These improvements include faster response times, reduced switching stresses of the power semiconductor devices, and reduced size and ratings of associated reactive components. The authors also present an analysis and design approach for three-phase SMR converters under large-input voltage and load variations. Output voltage control is achieved by varying the duty cycle of the inverter power semiconductor switches. Theoretical results are verified experimentally. >

Integrated traction inverter and battery charger apparatus

Abstract: An integrated traction inverter and battery charger apparatus which is capable of operating in either drive or charge modes. The apparatus integrates the components of a prior art three-phase inverter with an AC line-powered prior art DC source charger in a manner which recognizes that an input capacitor and certain components of a three-phase bridge inverter are capable of performing dual functions and thus can be active in both modes. Therefore, in the integration of the prior art devices some of the components are eliminated allowing savings in cost and weight of, and space required by, the components of the integrated inverter/charger apparatus.

A high-power multitransistor-inverter uninterruptable power supply system

Abstract: The active and reactive load distribution between n paralleled single-phase uninterruptible power supply (UPS) inverters is equalized by virtue of n-1 load-sharing control loops. The approach permits the construction of UPS systems of any desired power rating at maximum utilization of the power components. The method of harmonic cancellation decreases the switching frequency of the power devices while maintaining good dynamic performance. The design details of a 45 kVA UPS inverter system with 150% steady-state overload capability are presented. The performance under various operating conditions is illustrated by oscillograms. >

PWM technique for power MOSFET inverter

Abstract: A sinusoidal PWM (pulsewidth-modulated) inverter suitable for use with power MOSFETs is described. The output waveforms in the proposed PWM inverter are investigated both theoretically and experimentally. A modulating signal for the three-phase PWM inverter is obtained by adding the harmonic components of integer multiples of three to the three-phase sine waves. By using the proposed modulating signal, the amplitude of the fundamental component is increased about 15% more than that of a conventional sine-wave inverter and the commutation number of the inverter is decreased to two-thirds of a conventional one. >

An integrated AC drive system using a controlled-current PWM rectifier/inverter link

Abstract: Two identical three-phase, bipolar transistor, controlled-current, pulsewidth modulation (PWM) power modulators are integrated so that one functions as a rectifier and the other as an inverter in an AC drive system. The rectifier input currents maintain near-60-Hz sinusoidal waveforms with unity power factor. A leading power factor is also possible. The modulators do not depend on the availability of bidirectional switch elements. Performance as a polyphase induction motor drive under motoring and regenerative braking is reported. The study includes digital simulation of operation as a synchronous motor drive. >

A simple motion estimator for variable-reluctance motors

Abstract: A simple motion estimator for inverter-driven variable-reluctance motors is presented. The estimator probes unexcited phases with short voltage pulses from the inverter, and evaluates the resulting currents to measure the phase inductances. From these inductances, instantaneous motor position is estimated. Individual position estimates are optionally combined by a state observer to produce smoothed position and velocity estimates. Next, the secondary phenomena of eddy currents in the motor laminations, inverter switching noise, magnetic coupling between motor phases, and quantization introduced by digital implementation are all examined for their effects on estimator performance. Each phenomenon is addressed by a modification of the estimation. Finally, the estimator is evaluated experimentally using an inverter-driven three-phase motor having six stator poles and four rotor poles. The estimator is implemented digitally with an Intel 8031 microcomputer and little extra hardware. Further, it is embedded into a closed-loop controller of the inverter and motor. >

Static power conversion method and apparatus having essentially zero switching losses and clamped voltage levels

Abstract: A high efficiency power converter is achieved utilizing a resonant DC link between a DC source, such as a converter rectifying power from an AC power system, to a variable frequency voltage source inverter. A resonant circuit composed of an inductor and capacitor is connected to the DC power supply and to a DC bus supplying the inverter and is caused to oscillate stably at a high frequency to provide a uni-directional voltage across the DC bus which reaches zero volts during each cycle of oscillation of the resonant circuit. The switching devices of the inverter are controlled to switch on and off only at times when the DC bus voltage is zero, thereby eliminating switching losses in the inverter. The resonant circuit can be caused to oscillate utilizing pairs of switching devices in the inverter or a separate switching device across the capacitor, which again are caused to switch on and off only at times of zero voltage on the DC bus. For AC to AC conversion, enabling bi-directional power flow, the switching devices of the power source which converts AC power to DC power may have switching devices which are also switched only at the times of zero voltage so that switching losses in these devices is also minimized. A clamp limits the maximum voltage applied to the switching devices, thereby reducing voltage stresses on the devices, and preferably returns energy to the resonant circuit during each cycle of oscillation.

Back EMF sampling circuit for phase locked loop motor control

Abstract: A sensorless control for DC permanent magnet brushless motor includes a feedback loop connected between the motor stator windings and the inverter which controls the timer at which current is provided to the various windings in sequence. The control of the invention includes a voltage sensing network for sensing the back EMF on each motor winding when it is unenergized and comparing this voltage with a null point. For maximum torque this voltage has an optimum value and variation from this value produces an error signal which is integrated to produce a VCO drive signal. This signal controls the frequency of a VCO which in turn controls the switching times of the inverter.

Studies on inverter-fed five-phase induction motor drive

Abstract: The advantages of higher-phase-order drives are reviewed, and results of investigations of a five-pulse inverter-fed induction motor are presented. Methods of improving the waveform of the motor phase current in the five-phase drive are examined theoretically as well as experimentally. A mathematical model based on complex symmetrical components is developed for theoretical investigations, and a prototype five-phase inverter-fed induction motor drive is fabricated to conduct experimental studies. Theoretical and experimental results under various operating modes are presented. The studies establish that the five-phase drive operates satisfactorily when it is fed from a pulsewidth-modulated inverter. >

Bidirectional digital signal transmission system

Abstract: A system for transmitting digital signals over a transmission line including a driver of an inverter employing CMOS FET's and a termination of an inverter employing CMOS FET's A sense/control circuit at the termination senses changes in the operating condition of the driver inverter and in response thereto controls the operating condition of the termination inverter Under steady state conditions the termination inverter establishes the appropriate voltage at an output connection coupled thereto without dissipating any power

Deadbeat control of pwm inverter with modified pulse patterns for uninterruptible power supply.

Abstract: A modified algorithm of pulse-width-modulation (PWM) inverter deadbeat control suitable for uninterruptible-power-supply (UPS) systems is presented. Two state variables are measured at each sampling interval, then, using the data, the pulse width is computed in real time in order to force the output voltage equal to the reference at each sampling instant which is called the deadbeat control. Two kinds of PWM pulse patterns are used to increase the fundamental component of the output voltage, considering the microprocessor computation time. Experimentation and simulation has verified that the proposed control scheme increased the output-voltage amplitude, providing an excellent transient response and accurate phase positioning for various load conditions. This algorithm is suitable for applications of high-power UPS systems, in which the switching frequency is in the range of a few kHz and the precise control of power flow is required. >

Deadbeat control of PWM inverter with modified pulse patterns for uninterruptible power supply

Abstract: A modified algorithm of pulse-width-modulation (PWM) inverter deadbeat control suitable for uninterruptible-power-supply (UPS) systems is presented. Two state variables are measured at each sampling interval, then, using the data, the pulse width is computed in real time in order to force the output voltage equal to the reference at each sampling instant which is called the deadbeat control. Two kinds of PWM pulse patterns are used to increase the fundamental component of the output voltage, considering the microprocessor computation time. Experimentation and simulation has verified that the proposed control scheme increased the output-voltage amplitude, providing an excellent transient response and accurate phase positioning for various load conditions. This algorithm is suitable for applications of high-power UPS systems, in which the switching frequency is in the range of a few kHz and the precise control of power flow is required. >

Control strategy for a three phase AC traction drive with three-level GTO PWM inverter

Abstract: A control strategy developed for two-level inverters is applied to the three-level gate-turn-off PWM inverter. This is done by replacing the three-level inverter by two coupled two-level inverters and taking the coupling condition into account. A control strategy based on the method of direct self-control is described. Results from computer simulation for a traction motor with 1400 kW nominal power are shown and discussed. >

A new injection method for AC harmonic elimination by active power filter

Abstract: An injection method for an active filter which eliminates the harmonics present in AC lines by injecting PWM harmonic compensating current is proposed. In the proposed method, the active filter produces a pulsewidth modulation (PWM) current that cancels the existing harmonics up to any order completely. To generate such PWM current, both inverter and DC current source is needed. The current source can be replaced by a large inductor without any external power source. This can be achieved by providing the inverter with rectifying capability because the inverter has the same circuit structure as the rectifier. Therefore, the proposed model of PWM injection current includes not only the harmonic components to suppress the existing harmonics up to any order, but also the fundamental one, to raise the inductor current to any desired value. The characteristics of the injection method are investigated through a digital computer simulation. Feasibility is proved by the experimental results. >

A new family of resonant rectifier circuits for high frequency DC-DC converter applications

Abstract: A family of rectifiers suitable for operation at high frequencies is presented. These rectifiers use naturally occurring component parasitics to control diode switching thereby minimizing parasitic ringing and improving rectification efficiency by reducing the flow of harmonic currents. The input impedance of the resonant rectifier is linear, which makes possible an accurate adjustment of the rectifier to present the proper load impedance to an inverter. When a resonant rectifier is coupled to a resonant inverter in this manner, a fully resonant DC-to-DC converter is produced. With these circuits it is possible to achieve a very low input/output ripple and EMI since voltages and currents seen by the filters are confined to a very narrow frequency range compared to conventional squarewave converters. >

Automobile generator apparatus

Abstract: An automobile generator apparatus for producing commercial line power when driven by an automobile engine comprises a generator, an inverter unit, a controller for controlling the generator field and an accelerator actuator. The accelerator actuator is mounted opposite the accelerator pedal in such manner as to prevent erroneous operation thereof. The generator field is controlled while monitoring both the low-voltage side output and the high-voltage side output so as to prevent a large output current from flowing through the low-voltage side load. A circuit is further provided for preventing the occurrence of an overvoltage as a result of field control transistor malfunction. The switching elements constituting the output stage of the inverter unit are controlled to vary the duty ratio of the output waveform so as to stabilize the inverter output voltage and controlled to remove the center portion of the output waves so as to cope with the startup load. The inverter unit is also provided with an improved constant voltage circuit. There is further provided a synchronized operation control for combining the outputs of a plurality of automobile generator apparatuses. The generator is a single-shaft, dual-output type wherein the windings of the high-voltage side coils are disposed at the bottom of slots in the stator while the windings of the low-voltage side coils are disposed near the entrance of the slots.

A novel technique for optimal efficiency control of a current-source inverter-fed induction motor

Abstract: A technique that optimizes flux level to improve the efficiency of an induction motor is discussed. When harmonics and saturation effects are considered, the slip of minimum loss, or optimal slip, depends on both the speed and the load torque. The measurements of speed and torque are achieved without conventional torque and speed sensors, using motor terminal quantities. The control strategy is divided into two stages. First, the optimal slip is searched by trial and error, and the results are tabulated in microprocessor memory. Then the motor is operated at optimal efficiency by simply tracking the optimal slip given in the table. Experimental results show good performance in energy saving and dynamic responses. >

Nonvolatile semiconductor memory device

Abstract: PURPOSE:To reduce the power consumption by adding a circuit for executing a control so that a boosting circuit does not operate at the time of rise of a power source, operates only at the time of write/erasion, and a second voltage is generated. CONSTITUTION:When the power becomes ON, the potential of a connecting point 12 of a power-ON reset circuit 8 ascends gradually by a time constant determined by a resistance 9 and a capacity 10 from a ground level. Until the potential of the connecting point 12 reaches a threshold voltage of an inverter 11, the inverse of CON of a control signal from the inverter 11 remains an H level. In this case, an output 2 of a NOR gate 1 becomes an L level, and from a NAND gate 3, no clock CLK is outputted. When the potential of the connecting point 12 exceeds the threshold voltage, the inverse of CON becomes L, and in case when write/erasion are not executed, the inverse of W+E becomes H, the output of the gate 1 is L and the CLK is not outputted to a boosting circuit 6 from the gate 3. In case of executing write/erasion, the CLK is supplied, the boosting circuit 6 operates and the second voltage 7 is outputted, and write/erasion of an EPROM can be executed.

Discharge lamp driving circuit

Abstract: A circuit for operating a discharge lamp at a low frequency AC voltage while repetitively interrupting at a high frequency the voltage component to be applied to the lamp. The circuit includes at least one switching transistor for repetitively interrupting the voltage to be applied to the lamp at the high frequency, for example, 40 KHz so as to allow the use of a light and less bulky inductor as the current limiting conductor to be connected in series with the lamp. A bridge inverter is provided to have at least one pair of switching transistors for alternately reversing a DC voltage to apply the resulting AC voltage to the lamp at the low frequency, for example, 100 Hz low enough to stably operate the lamp without suffering from acoustic resonance. The high frequency component is bypassed through a bypass capacitor connected in parallel with the lamp. By reason of the inverter producing the low frequency AC voltage, the circuit requires all-off period during which the switching transistors of the bridge inverter are simultaneously off for preventing the short circuiting of the power source. An oscillation-inducing inductor is connected in series with the lamp in parallel relation to the bypass capacitor so as to form a series oscillating circuit which causes to flow an alternating oscillating current to the lamp circuit throughout the all-off period. The resulting oscillating lamp current continues for a longer time to thereby retard the deionization of the lamp. Accordingly, the all-off time can be extended to such an extent as to give greater flexibility in designing the circuit which is free from short circuiting of the power source as well as from the increased reignition voltage.

PWM technique for inverter with sinusoidal output current

Abstract: A sinusoidal pulse-width-modulated (PWM) technique suitable for single-chip microprocessor-based control is described. The proposed scheme can be considered as a digital alternative to the conventional subharmonic method in the sense that online real-time PWM control is possible and synchronization between carrier wave and signal wave is unnecessary. The scheme features a maximum output voltage that is 15% greater than for the subharmonic method, and the number of switchings is 30% less. A description of the PWM pulse-creation principle is given. Most invertor loads have a low-pass filter nature. Taking this into account, a performance function (PF), which is the time-integral function of the inverter output voltage, is introduced. An optimal PWM pattern is obtained by minimizing the distortion factor of the PF. As the calculation of the optimal pattern needs only three multiplications, it can be executed online with a minimum read-only-memory capacity using a conventional microprocessor. The experiment was carried out with an Intel 8096 CPU. The results demonstrate the validity of the proposed scheme. >