Discretized square wave extraction method and apparatus for IGBT coupling thermal impedance

Abstract

The invention provides a discretized square wave extraction method for an IGBT coupling thermal impedance. The method comprises: an IGBT is heated a conductive voltage drop of an FWD under a small current density is measured; the FWD is heated and a saturation voltage drop of the IGBT under the small current density is measured; according to the conductive voltage drop of the FWD and the saturation voltage drop of the IGBT under the small current density, junction temperature changing curves of the IGBT and the FWD are obtained indirectly and calculation is carried out to obtain a continuously-changing coupling thermal impedance curve; and fitting is carried out on the coupling thermal impedance curve to obtain coupling thermal impedance information of the IGBT and the FWD is obtained. According to the invention, with a simple method, the coupling thermal impedance of the IGBT module is extracted by measuring an end electrical feature quantity and then a perfect IGBT integrated thermal network model is established. The IGBT module is viewed as a black box and the internal packaging structure is ignored; under the circumstance that module packaging is not damaged, measurement of the coupling thermal impedance is realized based on discretized square wave measurement according to a principle of measuring thermal impedance by using an existing thermal sensitive parameter method. Moreover, the method has advantages of simpleness, effectiveness, fast response, and accurate measurement.

Description

technical field [0001] The invention relates to the field of power electronics, in particular to a method and device for extracting a discretized square wave of IGBT coupling thermal impedance. Background technique [0002] As an important part of the renewable energy power generation system and the electric drive system, the power converter works for a long time under the harsh working conditions of dealing with large-scale random fluctuations in power, and its reliability and expected service life are low. Insulated gate bipolar transistor (insulated gate bipolar transistor, IGBT), as the core component of power flow converter, is the component with the highest failure rate. Researching the reliability of IGBT is of great significance to improve the reliability of power converters. In actual application, because the power converter works for a long time under the harsh working conditions of dealing with large-scale random fluctuations in power, the junction temperature ins...

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Problems solved by technology

The infrared scanning method can be used to measure the junction temperature online to provide junction temperature data for thermal resistance calculation, but the module needs to be destructively unsealed, and due to the uneven distribution of chip surface temperature, the error between the measured junction temperature and the actual temperature is large. Causes a large deviation in the measured thermal resistance

Using the finite element analysis method, the accurate IGBT comprehensive thermal network model can be established through the finite element simulation software, which has the advantages of high precision and complex structure processing, etc., but this method strongly depends on the IGBT physical structure and the heat conduction characteristic parameters of each layer, and the relevant parameters It is not easy to obtain, and the simulation analysis time is long, the solution is cumbersome, and it cannot reflect the aging process of the module

The thermosensitive electrical parameter method is widely used because it does not need to destroy the packaging structure of the IGBT and does not require the physical structure parameters of the chip. However, multiple chips inside the IGBT module often share an external electrical port, and the existing conventional methods are difficult to pass. Measure the electrical characteristic quantity of the end to extract the coupled thermal impedance of the IGBT module

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