A single-phase PWM controlled AC to DC converter based on control of unity displacement power factor

A modified pulse-width modulation (PWM) technique that improves the displacement power factor and the input power factor of a single-phase AC to DC converter is discussed. The modified converter is shown to have a high input power factor and allows the of DC voltage from zero to more than the maximum value of the source voltage. The displacement power factor is unity, and the input power factor is almost unity in the wide range of current command </p

A control strategy of three-phase PWM inverter with fluctuating input voltage

A digital control strategy for the three-phase PWM inverter is proposed for a sinusoidal output with a fluctuating input voltage. The pulse width is computed by sampling and predicting the fluctuating input voltage every time the pulse generates. Three predictive methods are proposed. The errors and the waveform distortion of the output voltage are analyzed and discussed, along with the proposed predictive methods. The validity of the control method was experimentally verified using a microprocessor-based control system </p

Behavior of Transistor Switching in AC Chopper Circuit

In this paper, an AC chopper circuit, using a power transistor, is described which chops the AC voltage with a commercial frequency. The circuit is composed of a diode bridge and a power transistor in series with a load and capable of adjusting the switching frequency, fc, and the time ratio, T=ton/(ton+toff). The switching frequency and the time ratio of the AC chopper circuit depend on switching-times, that is, delay time, rise time, carrier storage time and fall time, especially in the high frequency. The upper limit of the switching frequency (about 150kHz) and the output characteristics of the circuit are investigated

Influence of Magnetic Saturation of Iron-Core on Performance of Thyristor Phase Control Circuit

The influence of magnetic saturation of iron-core on the performance of thyristor phase control circuit with series RLC elements is described. The circuit is analyzed by applying an approximate model of three straight lines to the flux Φ vs. current i curve of the iron-core reactor. And the influence on waveforms, r.m.s. values, power factor and response are discussed

Current commands for high-efficiency torque control of DC shunt motor

The current commands for a high-efficiency torque control of a DC shunt motor are described. In the proposed control method, the effect of a magnetic saturation and an armature reaction are taken into account by representing the coefficients of an electromotive force and a torque as a function of the field current, the armature current and the revolving speed. The current commands at which the loss of the motor drive system becomes a minimum are calculated as an optimal problem. The proposed control technique of a motor is implemented on the microprocessor-based control system. The effect of the consideration of the magnetic saturation and the armature reaction on the produced torque and the minimisation of the loss are discussed analytically and experimentally </p

A computative decision of pulse width in three-phase PWM inverter

A novel PWM (pulsewidth modulation) technique is proposed for a three-phase sine-wave PWM inverter. The pulse width is designed to produce a sine-wave output voltage by numerical calculation based on a geometrical technique. The accuracy of output voltage and the harmonics in an output voltage waveform are discussed and compared with the results of the conventional triangulation method. A modified method is introduced for obtaining a PWM inverter with fluctuating input voltage. The validity of the method is verified in an experiment using a microprocessor-based control system.</p

Fuzzy control of SMES for levelling load power fluctuation based on Lukasiewicz logic

&#60;P&#62;Provided that superconducting magnetic energy storage (SMES) is located near the consumer in the power system, levelling of fluctuating load power and compensation of reactive power can be achieved. Thus, loss in the power system can be reduced and the power system stability can be improved. An SMES control strategy for levelling the fluctuating load power based on Lukasiewicz logic is proposed. The control characteristics are discussed by comparing a simulation with the control results of other methods proposed by the authors. The variance achieved by the proposed method is smaller than those obtained with the other control methods. Thus, the proposed control method is superior to other control methods </p

AC Chopper Circuit with Lagging Reactive Load

An ac chopper circuit, which chops an ac voltage in a complete cycle for any lagging reactive load, is devised. The circuit is constructed of two ac-switches composed of power transistors and diodes. The load voltage is smoothly controlled by varying the time ratio of ac-switch. Transistors operate in a highfrequency chopping mode, thereby the ripples of the source current and the load current are easily filtered. Furthermore the input power factor of this model is better than that of the thyristor phase control circuit. In this paper, the construction and the driving method of this model are described

A single-phase PWM AC to DC converter with a step up/down voltage and sinusoidal source current

A pulse width modulation (PWM) AC-to-DC converter is proposed for a variable DC voltage supply. This converter has an advantage of controlling the DC voltage from zero to more than the maximum value of the AC source voltage and having a sinusoidal source current. The input characteristics and the control characteristics of DC voltage are clarified by computer simulation and they are confirmed by the experiment using a microprocessor-based control system. The dynamic characteristics are discussed by simulation and experiment </p

Analysis of Brushless-dc Motor Drive System Taking Account of a Load

In the power converter of ac drive system the switching behavior of semiconductors causes the distorted voltage and current waveforms, thus the drive characteristics are affected by them. It is, especially, an essential problem that the distorted current waveforms induce the torque ripple. It is assumed in the previous analysis that the input voltage of inverter is a ripple-free dc one. In industry, however, the input voltage of inverter is gained by rectifying the ac voltage. The torque ripple is caused by not only the behavior of inverter but also the behavior of converter. It is required to develop the analysis taking account of the both behaviors. In this paper, the analysis of brushless-dc motor drive system is proposed taking account of the ac supply, power converter, motor and load. This analytical method is the most suitable one for the analysis of practical system. The effects of factors, e.g. filter constants, inverter frequency, phase relation between ac supply and inverter cycle, load and inertia on the speed variation are revealed by this analysis. Further, the decision of filter constants is discussed from a view of speed variation