S.B. Dewan

A PWM AC to DC converter with fixed switching frequency

For a PWM (pulsewidth-modulated) AC-to-DC converter, a predicted current control strategy with fixed switching frequency (PCFF control) is proposed. Its principle and implementation are described, and experimental results are provided which show that the converter under PCFF control has bidirectional power transmission ability with high dynamic performance. The line currents are close to sinusoidal with unit power factor. The PCFF control produces a better switching pattern than hysteresis current control. This results in a reduction of harmonics in the line currents and lower stress on the switching devices.<<ETX>>

Analysis of an AC-to-DC voltage source converter using PWM with phase and amplitude control

A comprehensive analysis is presented of a pulse-width modulated AC-to-DC voltage source converter under phase and amplitude control. A general mathematical model of the converter, which is discontinuous, time-variant, and nonlinear, is first established. To obtain closed-form solutions, the following three techniques are used: Fourier analysis; transformation of reference frame; and small-signal linearization. Three models, namely, a steady-state DC model, a low-frequency small-signal AC model, and a high-frequency model, are consequently developed. Finally, three solution sets, namely, the steady-state solution, various dynamic transfer functions, and the high-frequency harmonic components, are obtained from the three models. The theoretical results were verified experimentally.<<ETX>>

Analysis of a PWM AC to DC voltage source converter under the predicted current control with a fixed switching frequency

A detailed analysis of a pulse-width modulated AC to DC voltage source converter under the proposed predicted current control with a fixed switching frequency (PCFF) is presented. A steady-state analysis, a dynamic response analysis, a high-frequency component analysis, and their solutions are also provided. The results show that the converter under the PCFF control has a fast dynamic response, ease of control, and a good switching pattern. The theoretical derivation is experimentally verified. >

PWM-CSI inverter for induction motor drives

A number of issues involved in designing a current source inverter system for a large induction motor drive are discussed. Using two modulation techniques-selective harmonic elimination in the upper frequency range and trapezoidal modulation in the lower frequency range-control of voltage, current, and torque harmonics is achieved while limiting the gate turn-off switching frequency to 180 Hz. Each modulation range is divided into a number of subranges to exploit the available switching capacity and to avoid harmonic resonances involving the capacitor and the motor inductance. In addition to basic principles, simulation waveforms and test results are included from a laboratory experimental system.<<ETX>>

Generalized techniques of selective harmonic elimination and current control in current source inverters/converters

This paper presents generalized techniques for realizing PWM patterns which provide selective harmonic elimination and current magnitude modulation (SHEM) for current source inverters/power converters (CSI/C). A combination of chops and short circuit pulses are positioned in such a way that lower order harmonics are eliminated selectively besides current magnitude modulation with minimum switching frequency. Generalized equations and tables which show the relationship of various PWM-SHEM parameters to the position of short circuit pulses and the number of chops per 30/spl deg/ are provided and discussed in detail. >

A large-scale PWM solid-state synchronous condenser

The description, steady-state analysis, and the closed-loop control design of a microcontroller-based large-scale pulsewidth-modulated solid-state synchronous condenser (PWM-SSSC) for reactive power compensation are presented. The key advantage of PWM-SSSC over its predecessors is the fact that large passive magnetic components are replaced by silicon. This provides a more compact and efficient systems at a cheaper price. A series of PWM switching patterns in the low-switching-frequency range (F/sub SW/<500 Hz), which are most suitable for high-power gate turn-off (GTO) thyristors, is presented. Formulations and solutions of the Newton-Raphson method for possible low-switching-frequency PWM patterns, performance comparisons for multiple solutions, different control strategies, and the filter design are presented. Cumbersome z-domain methods for pulsed stability analysis are completely avoided by using direct s-domain computations. A systematic approach for tuning the controller parameters is introduced by extending the concept of absolute stability.<<ETX>>

General Analysis of Three-Phase Inverters

A method of analysis for three-phase inverters is described. The method is based on Park vectors [1], [2] and predicts the waveforms of inverter quantities under various load conditions. The procedure discussed can be used to determine the commutation sequence of a pulsewidth modulated inverter. The current distribution of the inverter can be obtained from the current vector. The vectors of the inverter voltage and currents are determined for passive R-L and R-C loads. Oscillograms of the current vectors are shown for different loads.

Analysis of a PWM AC to DC voltage source converter under predicted current control with fixed switching frequency

A detailed analysis of a pulse-width modulated AC-to-DC voltage source converter under the proposed predicted current control with a fixed switching frequency (PCFF) is presented. It includes a steady-state analysis, various dynamic response analyses and a high-frequency component analysis. The results show that the converter under the PCFF control has a fast dynamic response, ease of control, and a good switching pattern. The theoretical derivation is experimentally verified.<<ETX>>

Synchronous Motor Drive with Current-Source Inverter

Steady-state properties of a variable-speed drive using a synchronous motor fed by a controlled current-source inverter are derived from an equivalent circuit model, including saturation, and are confirmed by experiment. The system is shown to be stable under all operating conditions. Control strategy for open-loop operation is discussed.

A comparison of power circuit topologies and control techniques for a high frequency ballast

A comparison of power circuit topologies and fluorescent lamp current control strategies for medium to high power rapid-start high-frequency ballasts is presented. Issues such as output current harmonic content, current crest factor, and starting current are addressed. It is found that the LCC type and the LCLC type power converter satisfy the lamp requirements. The LCLC type converter has the added advantage of having the lowest kVA rating. Experimental results for the LCC type power converter under voltage mode control are provided.<<ETX>>