| 摘要 |
A line-commutated converter is connected in series, on the DC side, with a converter which can be positively commutated and with a load, both converters being supplied from the same power supply. The converters are driven such that the controllable valves of the converter which can be positively commutated are triggered by approximately the same control angle (- alpha ) before the natural commutation time which is common to both converters, at which (+ alpha ) the corresponding controllable valves of the line-commutated converter are triggered after this commutation time. This is achieved by means of two sawtooth-waveform voltages (SZu, SZu) which are offset through 180 DEG electrical and are in each case compared with an adjustable voltage (Vi-VB or -Vi-VB respectively). This approximately symmetrical triggering is effected in that the mean values of the output voltages of the two converters correspond. A superimposed control-angle regulation can be provided in order, for example, to compensate for the influence of the overlap angles caused by the commutation and to keep the mean values exactly the same. The method is suitable, in particular, in the case of a DC motor for multi-quadrant operation. <IMAGE>
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