Abstract-A dual gate-turn-off thyristor current-source converter topology with sinusoidal inputs is proposed for high-power applications. The sinusoidal input current is realized by using pulsewidth modulation techniques to eliminate 11th and 13th harmonics and a transformer to cancel 5th, 7th, 17th, and 19th harmonics. Three switching patterns are proposed with a switching frequency of 360 or 420 Hz. The combination of these switching patterns provides a full-range control over the dc output current. Resonant modes of the proposed system are identified, and the criterion for the line capacitor design is provided. Simulation and experimental results are given to verify the theoretical analysis.

Abstract-A novel rectifier topology for high power (0.5 to 10 MVA) current source based ac motor drives is proposed. This rectifier is composed of a multi-winding transformer, a multi-level diode rectifier and a modified multi-level buck converter. The rectifier produces near unity input power factor and sinusoidal input current under any operating conditions. In addition, the proposed rectifier features reliable operation and low manufacturing cost. In this paper, the operating principle of the proposed rectifier is introduced. A number of design issues are investigated, which include PWM switching patterns, input power factor and line current harmonic distortion. Some design considerations such as the effect of the line inductance discrepancy on system performance are addressed. Experiments on a 5 kVA/208V four-level prototype are carried out for verification.Index Terms-Buck converter, medium voltage applications, multilevel converters, power factor control.

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-This paper presents a unique PWM switching pattern and a novel power factor control scheme for high power GTO ac/dc converters. This switching pattern has a switching frequency of 360Hz, which is the lowest possible frequency to achieve 5th and 7th harmonic elimination and an adjustable dc output current simultaneously. Using both feedback and feedforward control techniques, the proposed power factor control scheme can keep the converter input power factor at unity or a maximum achievable value. Simulation and experimental results are given to confirm the proposed PWM pattern and power factor control scheme.

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