Search

This paper presents a three-phase voltage-source 36-pulse converter that draws almost sinusoidal currents. The converter results from the combination of a series-connected 12-pulse voltage-source rectifier with a passive voltage-injection circuit and a bidirectional switch, referred to as hybrid injection. The voltage-injection circuit uses a single-phase rectifier bridge and a single-phase transformer. Both the voltage-injection circuit and the bidirectional switch operate at six times the supply frequency and have a low rating. In this paper, the converter operation is explained and analyzed. Subsequently, the converter is evaluated experimentally using a 4-kW 400-Hz prototype, where the [THD.sub.I] of the line currents was measured to be below 1.2%. Index Terms--AC-DC power conversion, aircraft power systems, power quality, rectifiers.

A three-phase, multilevel rectifier using active voltage injection with one MOSFET device is presented. The injector consists of a bidirectional switch that modifies the behavior of a 12-pulse rectifier resulting in either 24-pulse or multilevel pulsewidth-modulated (PWM) operation. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for 24-pulse operation and 1.06% for PWM operation. The MOSFET current is 2.9% of the load current. The circuit operation, idealized waveforms and modulation strategy are explained and experimental results are presented. Index Terms--High-power factor rectification, three-phase multipulse rectifier.

A new converter topology for a three-phase multi-pulse rectifier circuit is described. This converter draws almost sinusoidal currents from the ac system with very low harmonic content and typically less than 3% total harmonic distortion. The topology uses only passive components and has a lower component count than other rectifier circuits with similar performance. Two six-pulse rectifier bridges are connected in series, fed by a series connection of transformers, to form a 12-pulse system. An additional low power harmonic injection circuit enhances the performance of the circuit to obtain low harmonic current pollution levels that are comparable with those achieved from a 24-pulse rectifier. The circuit operation is explained and experimental results are presented. Index Terms--Autotransformers, rectifier bridges, sinusoidal currents, three-phase multipulse rectifier circuit.

Two techniques are presented to balance the filter capacitor voltages of a multipulse rectifier with the active injection operating on a variable-frequency supply. The active injector consists of a low-rated bidirectional switch that modifies the behavior of a 12-pulse rectifier at either low or high frequency, resulting in 24-pulse or multilevel pulse width modulation operation, respectively. The operation of the rectifier and the injector, the practical issues that unbalance the capacitor voltages, and the methods to correct this imbalance are explained together with experimental results obtained with a 4-kW prototype. [ABSTRACT FROM AUTHOR]