CONVERTER DEVICE AND CORRESPONDING METHOD

It is presented a converter device arranged to convert power between a first high voltage direct current, HVDC, connection, a second HVDC connection and an AC connection. The converter device comprises: a first power converter comprising a phase leg provided between terminals of the first HVDC connection, the phase leg comprising a positive arm, an inductor, an AC connection and a negative arm. Each one of the positive arm and the negative arm comprises converter cells and one of the converter cells is a first host converter cell. Each converter cell comprises two main switching elements and a storage element, the two switching elements being arranged serially in parallel with the energy storage element. The converter device also comprises a power converter section comprising a first converter cell comprising at least two switching elements connected serially in parallel with the energy storage element of the first host converter cell. The converter device is arranged to control the switching elements of the first switching element string in dependence of the state of the main switching elements of the first host converter cell.