IMPROVED PROTECTION METHOD FOR A SEMICONDUCTOR MODULE BASED CHAIN-LINK OR MMC CELL BY A DC CROW-BAR

A control device for an arrangement of switches, the switches being arranged to form at least one current path or branch, wherein each of the at least one current paths or branches comprises two switches and wherein two AC terminals (AC1, AC2) being connected to the current paths and wherein the control device being adapted to monitor and determine an electrical condition of any of the switches, based on predetermined measurable conditions and wherein the control device is further adapted to output a control signal, if a predetermined threshold of the monitored and determined conditions is reached and/or exceeded for a specific amount of time, wherein the control signal is inputted into a semiconductor based short-circuiting device for activation of said device, wherein the semiconductor based short-circuiting device is switched electrically parallel to the current paths and is further configured to short-circuit the two AC terminals (AC1, AC2) and to short-circuit a capacitor, switched electrically parallel to the current paths, in such a duration of time, that a majority of energy stored in the capacitor is dissipated in the semiconductor based short-circuiting device and a minority of the energy stored in the capacitor is dissipated in the switches.