Novel stabilisation algorithm for the DC-link of a 3-level-NPC converter with active front end

Examples of typical applications for three-level NPC inverters are the operation of high power induction machines e.g. for mining applications or generators with active front ends in wind energy plants. This type of inverter needs balancing of the DC-link. In order to achieve an optimal volume to power ratio and minimal losses, a control based method will be used. Especially in mining applications there are strict requirements on safety, e.g. the drive must be electrically disconnected from the inverter in case of failure or emergency. A new method to control and stabilize the DC-link voltage, which considers these requirements, will be presented. The developed method is then tested in different scenarios and, lastly, used for the control of a complex mechanical simulation model.