Research Of Parameter Extraction Method And Key Characteristic In Transient Commutation Loop Of Power Converter

Affected by the coupling characteristic between the stray parameters and the power devices,the commutation transient in power electronic converter contains significant nonlinear phenomenon.The evaluation of key parameters,including voltage stress and switching loss,and the extraction of the stray parameters in the commutation loop are essential steps.They contribute to the analysis of the robustness and reliability of the power electronic system.For improving the accuracy of parameters extraction results and achieving the analysis of the key characteristic in commutation loop,a frequency-based stray parameters extraction method is established.The quantitative analysis for typical parameters in switching transient is studied.The above research breaks through the test range limitation of the traditional stray parameter extraction method,and the extraction accuracy is greatly improved.Also,the field-circuit coupling analysis for reverse recovery process reveals the influence mechanism of the key parameters,and the calculation results provide new method for evaluating the design of power converter.Firstly,a frequency-based extraction method for stray parameters in commutation loop is proposed.Based on the frequency characteristics of the switching transient in silicon carbide device,the stray inductance and parasitic capacitance in vital section of the commutation loop can be accurately extracted.This frequency-based extraction method of stray parameters has low test cost and easy data processing.Compared with the traditional time-domain extraction method,it overcomes the problem of bandwidth matching and synchronization between current and voltage probes,and avoids errors caused by artificial selection of test periods.The extraction range and accuracy are greatly improved.In addition,this method can also be used to extract equivalent series inductance in capacitor and stray inductance in power device package.Secondly,the quantitative analysis method of the key parameters during the reverse recovery process in freewheeling diode is explored in stages.Based on the interactive principle between the commutation circuit and the device semiconductor,the calculation expression of the key parameters in the reverse recovery process is theoretically deduced.The field-circuit coupling model is established to verify the accuracy of the interactive analysis.The results show that the current dropping slope and other parameters are only determined by circuit-related factors,while the voltage overshoot,turn-off loss and other parameters are affected by the chip structure,doping concentration and other semiconductor parameters with the circuit parameters such as stray inductance.In addition,the quantitative calculation results of key parameters can be used to evaluate the rationality of device selection and circuit design in the converter.Finally,the parameters and key characteristic analysis in commutation loop is simulated and experimentally verified.A portable stray parameter extraction platform is designed to achieve accurate extraction of stray parameters from laminated busbars,copper busbars,DC capacitors and power devices.In addition,the simulation and experimental comparison of the diode reverse recovery process verify the calculation accuracy of the key parameters.