Abstract: In a power-electronic circuit arrangement for compensating for mains system voltage reductions and mains system disturbances, a second auxiliary voltage source is provided, whose voltage is chosen to be less than that of the first auxiliary voltage source. The second auxiliary voltage source can be coupled to the feeder converter with the aid of a switch. The circuit according to the invention can thus operate in two different modes: when the first auxiliary voltage source is coupled to the feeder converter, the available voltage is sufficiently high to compensate for mains system failures or mains system voltage reductions. However, when less severe disturbances occur, the second, lower auxiliary voltage source is coupled to the feeder converter, and mains system disturbances can in consequence be compensated for without any major switching losses.

Abstract: An invertor having a plurality of invertor bridges which operate in parallel and whose output voltages are summed. The invertor bridges are driven with pulse duration modulation according to an auxiliary control voltage. The auxiliary control voltages of the individual invertor bridges have a constant phase difference between one another. The output voltages of the bridges are summed by a center tap which is grounded by a ground connection. Effective suppression of the common-mode current distortion is achieved by having the switch arranged in the ground connection.