Research in the field of power devices has led to the development of power semiconductors that allow high switching frequencies. Especially the IGBT (Insulated Gate Biploar Transistor) is suitable for three-phase ac-to-dc converters in the medium power range (1 kW - 100 kW).
Because of the high switching frequencies the harmonic contents of the line-side converter voltages can be kept small, which results in reduced line-side reactors compared to conventional converter systems.
For full exploitation of the capability of the new devices appropriate pulse width modulation (PWM) is necessary.
This paper studies the reasons for line current distortion caused by a three-phase ac-to-dc converter in order to conclude the requirements for appropriate PWM schemes.
Quality criteria for the selection of the best PWM schemes are presented. The quality criteria are then applied under consideration of minimum switching state time of the converter valves.
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