HARMONIC CORRECTION OF 3-PHASE RECTIFIERS AND CONVERTERS

摘要

An AC-DC converter for connecting an AC supplyand a DC has a rectifier, and a harmonic correction circuitformed of (a) thyristor inverter legs connected at a commonoutput point to form a Y switch, or separately at positiveand negative terminals and (b) a voltage selection circuitfor selecting a voltage derived from one of the positiveand negative DC rails, or the AC lines, to control currentshape and turn-off the thyristors. The thyristors areturned on by, and may also be turned off by, a controller.The voltage selection network may be a resonant circuitthat uses ramping of the voltage at the outputs from thethyristors to turn the thyristors off or switchescontrolled by the controller. A converter for converting DCto AC power has an inverter bridge, a DC input lineinductor on each DC rail, a generator for generating awaveshape output that has a frequency equal to the numberof AC lines times the frequency of the AC supply; and amultiplexer for multiplexing the output of the generatoronto the AC lines to reduce total harmonic distortion ofcurrent in the AC lines. The DC to AC converter may use thethyristor networks used for the AC to DC converter for themultiplexing function, under control of the controller. Thegenerator may be a voltage selection network or switchnetwork that selects a voltage source from one of thepositive DC rail, the negative DC rail and a center tap onthe DC rail.6-