Control of parallel connected power devices

An arrangement for controlling semiconductor power switches in parallel connected power devices,

• wherein the semiconductor power switches of each parallel connected power devices are arranged to connect either the positive or the negative pole of the intermediate DC-voltage of respective power device to an output phase of the power device,
• wherein at least one output phase of each power device of the parallel connected power devices is connected to a common output terminal such that the common output terminal is connected to at least two output phases,
• wherein:
• the arrangement is arranged to measure the voltages of output phases, which are connected in parallel, for the parallel connected power devices,
• to calculate the timing differences of output voltage state changes on the basis of the measured output voltages of at least two power devices of the parallel connected power devices, the calculating of the timing differences includes comparing a timing of each measured output voltage of the output phases for determining differences in timing of the output voltages of the output phases connected in parallel, and
• to advance or delay the control signals of the semiconductor power switches on the basis of the calculated timing differences such that the output voltage state changes in the phases which are connected together via output impedances occur as desired time instants.