Blanking-time effects in the context of modular multilevel converters

Blanking-time (or blocking-time) effects in power-electronic converters have been known since long. They introduce disturbances which are not easily handled by control means. Their compensation is not straightforward, because they depend on the sign (direction) and to a much lesser degree on the magnitude of the current flowing through the switching devices. Depending on the topology of the converter and the relation between blanking time and pulse period, the influence on the output quantities is relevant. This paper analyses blanking-time effects based on measurements performed on a modular multilevel converter - where these effects also influence the harmonic content of the DC voltage considerably. A straightforward FPGA-based compensation mechanism is implemented and its mitigation effect documented.