Circuit and method for measuring stray inductance of current conversion circuit of three-level converter

Abstract

The invention discloses a circuit and a method for measuring stray inductance of a current conversion circuit of a three-level converter. The circuit comprises a first IGBT (insulated gate bipolar transistor), a second IGBT, a third IGBT, a fourth IBGT, a first clamp diode, a second clamp diode, a first resonant capacitor, a second resonant capacitor, a first direct-current support capacitor, a second direct-current support capacitor, a laminated busbar, a direct-current power supply and a freewheel reactor. The method includes forming different freewheel circuits by the freewheel reactor; exerting double pulses to each corresponding IGBT; taking an average value of resonance current frequencies at a turn-on moment and a turn-off moment; and precisely computing the stray inductance of the current conversion circuit by an LC parallel resonance characteristic realized by the resonant capacitors and the stray inductance of the circuit. The circuit and the method have the advantages that actual operation is facilitated, the stray inductance of the current conversion circuit of the three-level converter can be accurately measured, overvoltage levels of a power device under different current grades of the three-level converter can be accurately controlled conveniently, and accordingly establishment of a system control strategy can be guided.

Description

technical field [0001] The invention relates to the application field of power electronics, in particular to a measuring circuit and a measuring method for the stray inductance of a commutation circuit of a three-level converter. Background technique [0002] With the improvement of the power level of the power conversion system and the development of power electronics technology, the power density of the IGBT (insulated gate bipolar transistor) module is getting higher and higher, and the turn-on and turn-off performance is getting better and better, which means that the turn-off current and its slope is getting bigger and bigger. At this time, a voltage will be induced on the stray inductance of the commutation circuit of the three-level converter, and the voltage, together with the DC bus voltage, will be directly added to both ends of the turned-off IGBT, which may exceed the rated voltage of the IGBT and cause the device damage. Therefore, accurately grasping the valu...

AI Technical Summary

Problems solved by technology

[0003] There are two large commutation circuits and two small commutation circuits in the three-level converter. Since the commutation circuit contains multiple power devices, and the equivalent stray inductance of power devices is an order of magnitude different from that of laminated busbars Therefore, it is not possible to accurately judge the overvoltage level of the IGBT at a certain current level only by relying on the stray inductance value of the laminated busbar.

The traditional stacked busbar stray inductance test method relies on the voltage drop of the device at the moment the IGBT is turned on or off, so the measured results do not include the equivalent stray inductance of the IGBT itself, and the measurement process requires the current to be stable during the voltage drop period. The rate of change, the accuracy of the measurement is closely related to the test conditions

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