| 摘要 |
<p>In an apparatus for converting alternating voltage to direct voltage and conversely with a series connection of at least four units (1-4) each comprising a semiconductor device (10-13) of turn-off type and a diode (14-17) connected in anti-parallel therewith between two poles of a diode voltage side, a flying capacitor (25) is connected between two outer midpoints (24, 26) between two units of the series connection, while the midpoint of the series connection is connected to an alternating voltage phase line (19). An arrangement (27) is adapted to control the units (1-4) for transferring the apparatus between a main operation mode and an alternative operation mode depending upon function parameters of the apparatus. The semiconductor devices of the outer units (1, 4) are then kept continuously turned on in the alternative operation mode and only semiconductor devices of the inner units (2, 3) are then switched. The control arrangement (27) controls the voltage of the pulses on the phase output (18) of the apparatus to be lower in the alternative operation mode.</p> |
