Monitoring of paralleled IGBT/diode modules

A method is presented to monitor the state of a converter with an unlimited number of paralleled insulated gate bipolar transistor (IGBT)/diode modules with individual gate drives. The monitoring functions can be implemented without extra signal processing or load-side components. The method is based on the active gate-controlled current balancing (CB) principle. This principle is reviewed in the first part of this paper, and the necessary supplements to implement the monitoring functions are shown. In the second part, experimental measurements are shown. This new control method allows monitoring the state of a converter and balancing the losses and current sharing between paralleled power devices, without the need to match the devices nor the gate drives. Thus, the overall reliability can be increased without increasing the costs. Since no matching of the devices is needed, the handling and logistic costs can be significantly reduced. IGBT/diode modules for standard paralleling are selected, and only modules of the same class can be paralleled without excessive derating. The presented method allows switching off one of the paralleled branches in the case of parameter degradation and to keep the converter operating at a lower power.