On-line measuring method of high-power IGBT collector current

The on-line measurement of the high-power IGBT collector current is important to the hierarchical control and short-circuit and overcurrent protection of its driver and the sensorless control of the converter. The conventional on-line measurement methods for IGBT collector current are not suitable for engineering measurement such devices as the large-size, high-cost, low-efficiency sensor, current transformer or divider, etc. Based on the gate driver, the paper uses a resistance capacity circuit paralleled with the IGBT power emitter and auxiliary emitter terminals to fulfil the IGBT collector current on-line estimation by measuring the capacity voltage. The theoretical analysis verifies the feasibility of this method. However, the very small resistance of IGBT power emitter leads to the narrow bandwidth of the estimated current. The improved method is adopted to increase the accuracy of current estimation and solve the problem of narrow bandwidth existing in the high-power IGBT steady-state collector current. The simulation and experiment results prove the method to feasible and effective.