Research On Condition Assessment Method Of IGBT Module Based On Short Circuit Current

The increasingly serious energy crisis and deteriorative ecological environment have brought more issues that are prominent to the sustainable development.With the development and maturity of new energy generation technology,as a clean and renewable energy,wind energy has received unprecedented attention.Following a surge in installed capacity of wind power every year,wind power is becoming crucial to solve the current energy crisis.According to the data of the practical engineering application for many years,the power converter,a core component of wind power generation,is one of the weakest links in the wind power system with a highest failure rate of Insulated Gate Bipolar Transistor-IGBT.In the whole wind power system,the converter is responsible for the energy transmission.However,the great randomness of wind energy and the fluctuation of wind generation power will cause the junction temperature of IGBT module to fluctuate violently,and the great difference of thermal expansion coefficient of IGBT module packaging materials will be easy to cause the poor reliability problems such as common bond wire fatigue and solder layer fatigue etc.The failure of the converter can affect the normal operation of the wind turbine,and even leads to a serious grid accident due to large-scale wind power off the grid.It can be seen that the reliability of IGBT power module is vital to the safe and stable operation of the whole wind power system.It is required to assess and judge the current condition of the IGBT module in the system,decide whether to overhaul and maintain the equipment or change the device degraded to a certain extent according to the judging results to ensure the safe and stable operation of the whole system.This paper presents a method of condition assessment on IGBT devices' performance degradation.Test the value of short-circuit current of the IGBT module under a specific drive voltage by maintaining normal bus voltage.Then judge the sound condition of IGBT module according to short-circuit current value and its varation.The main work of this paper is as follows:Firstly,the paper ravels out the aging mechanism of IGBT module in detail,and analyzes the relationship between the performance degradation and short-circuit current of IGBT module theoretically.What's more,it analyzes the influence of bus voltage and junction temperature on short-circuit current.According to the method proposed in this paper,by measuring short-circuit current value of IGBT module under specific drive voltage and analyzing its variation,the influence of bus voltage and junction temperature can be eliminated,and the condition of IGBT module is directly judged.Secondly,this paper establishes an equivalent resistor network model of IGBT device emitter by analyzing the IGBT chip and its packaging structure characteristics in detail based on the physical structure of semiconductor.In this paper,a qualitative analysis of the relationship between the resistances of resistor network model is conducted,and the influence of resistance variation on the equivalent resistance value of resistor network as two-port network is analyzed.Finally,a simulation model is set up in Simulink to simulate the change of current path and current redistribution of IGBT current from emitter chip to copper substrate caused by resistance change.Finally,the correctness of the proposed method of condition change assessment is verified by experiments.An adjustable voltage drive circuit for IGBT short-circuit current measurement is designed to enable the IGBT to work in a short-circuit condition under a specific driving voltage.In the experiment,a test platform of IGBT short circuit is built and the performance degradation of IGBT is simulated by cutting off bond wire.The next is to test IGBT module's short-circuit current in different simulated aging mode when the bond wire is cut off.After processing and analyzing the percentages of short-circuit current deviations in various modes,a well-defined state interval is obtained,and in-depth study is conducted on the simulation degradation mode closest to the actual working conditions.At the same time,the change of the saturation voltage drop under the corresponding degradation mode is tested.The state zone of the percentage of saturation voltage drop deviation value is basically the same as the state zone with the percentage of the short-circuit current deviation value.The experimental results confirm to the theoretical analysis basically,which verifies the correctness of the IGBT module condition assessment method based on short-circuit current proposed in this paper.