METHOD IN A CASCADED TWO-LEVEL CONVERTER, CONTROL DEVICE AND COMPUTER PROGRAM PRODUCTS

摘要

The invention relates to a method (20) for providing a switching order signal to a cell (21..., 2n) of a cascaded two-level converter (1). The (21..., 2n) comprises a capacitor parallel-connected with two series-connected semiconductor devices (3a, 3b). The cascaded two-level converter comprises two or more of the cells cascade connected and arranged in a phase, divided into two phase arms (7, 8), between a first pole (4a) and a second pole (4b) of a direct voltage side. The method (20) is characterized by the steps of : measuring (21) voltages of the capacitor of the cell; calculating (22) a compensated voltage reference based on a voltage reference and the measured voltages of the capacitors, wherein the voltage reference corresponds to a desired ac current to be output on an ac-side; using the compensated voltage reference (r) to calculate a switching order signal, and providing the switching order signal to the cells (21..., 2n).