Abb Technology Ag

Anders J Pettersson

Gunnar Asplund

Lennart Harnefors

Roland Siljeström

Lars Döfnäs

A device for converting a DC voltage into an AC voltage and vice versa comprises a control system to control the voltage conversion and at least one phase leg () with a first (Uvp) voltage source connected in series between a first DC terminal () and a first AC terminal () and with a second (Uvn) voltage source connected in series between the first AC terminal () and a second DC terminal (). Each of the voltage sources comprises at least a first and a second submodule () in series-connection, where each submodule () comprises at least two power electronic switches () connected in parallel with at least one capacitor (). The control system comprises a central control unit () and at least two subunits (), where the central control unit () transmits to each subunit () a reference AC voltage (ua_ref) and a switching carrier signal (s_sw) and where each subunit () controls the switching of the power electronic switches () of one of the submodules () according to a PWM pattern so that each time the switching carrier signal (s_sw) crosses the reference AC voltage (ua_ref) either the voltage across the capacitor () or a zero voltage are applied to output terminals () of the corresponding submodule ().

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Ludvika, Sweden

Anders J Pettersson