On-state voltage drop based power limit detection of IGBT inverters

Power density is a key performance factor in order to reduce the cost and size of a power converter. Because of the unknown junction temperature, today´s design margins are relatively high to ensure safe and a reliable operation. In this paper, the on-state voltage drop is measured online for all insulated gate bipolar transistors (IGBTs) in the inverter, using advanced gate driver. The die temperature is estimated and monitored on each device during power converter operation. Based on the monitored temperature in real time, the maximum power capability is detected. The output power is increased until a safe operating temperature of power modules. This enable a power density is increased by 11.16 kW /litre to 19.13 kW /litre in a low voltage power stack which is typically used in wind power converters. Experiment results are shown for safe operation of converter at around 1.2 MW, which is built in a standard size for the 600-700 kW. Furthermore, the 1700 V, 1000 A power module is replaced with a 1400 A module to increase the load current.