Serial-Parallel IGBT Connection Method Based on Overvoltage Measurement

This paper deals with a novel method which allows the serial connection of Insulated Gate Bipolar Transistors (IGBTs). The different dynamic characteristics of serially connected IGBTs during turn ON and OFF cause a short-term overvoltage stress in the transistors. In contrary to the commonly used techniques, the presented method reduces additional commutation losses by actively correcting turn ON and OFF delays. The presented method uses overvoltages as measured by a peak detector. The correction circuit doesn't require a high speed Analog-Digital converter (ADC) or high speed computation. The target power switch unit consists of two serial connected transistors with two identical parallel branches. The well-known 2-level inverter topology equipped with the power switch unit can be connected directly to the high-voltage grid. This converter topology was demanded by our industry partner for 11 MW mining machines. The paper contains a laboratory experiment conducted on a serial-parallel IGBT power switch unit with a tested output power of 1 kW.