| 摘要 |
<p>An apparatus for converting a direct current into an alternating current comprises a direct-current converter (1) having an input and an output, which direct-current converter is continuously controllable, a capacitor (C), and a control unit (4) for controlling the direct-current converter. The apparatus furthermore comprises a second direct-current converter (2) having an input and an output, wherein the input of the second direct-current converter is connected in parallel to the input of the first direct-current converter and the outputs of the first and the second direct-current converter are connected in series. An unfolding bridge (3) is connected to the series-connected outputs of the direct-current converters, whilst the capacitor is connected to the output of the second direct-current converter. Furthermore, a first switching element (S1) is provided for interrupting the series connection and a second switching element (S2) is provided for connecting the unfolding bridge to the output of the first direct-current converter in the interrupted state of the series connection. The control unit controls at least the first switching element in dependence on the voltage Vc across the capacitor and the voltage Vabs across the unfolding bridge, in such a manner that the first switching element is opened when Vabs < Vc. <IMAGE></p> |
