IMPROVEMENT OF THE IGBT MATHEMATICAL MODEL WITH NONLINEARITY OF JUNCTION CAPACITANCES
Journal Title: Вісник Кременчуцького національного університету імені Михайла Остроградського - Year 2018, Vol 1, Issue 108
Abstract
Purpose. To improve the IGBT mathematical model in state variables, which takes into account the dynamic capacitance of semiconductor junctions between the terminals of the device. Methodology. Theoretical research is based on Darlington scheme for the representation of IGBT, Kirchhoff laws, the transients theory in electric circuits, the superposition method and the methods of mathematical analysis. IGBT is represented by the equivalent circuit, which includes a controlled current source, that implements a family of static volt-ampere characteristics of the transistor, as well as voltage variable capacitors, which represent parasitic capacitances between the transistor leads. The driver rep-resents by source of the pulse EMF, which is applied through the ballast resistor to the gate of the transistor. Results. The mathematical model of IGBT in state variables has been improved. The model differs from the known by taking into account the dynamic capacitance of semiconductor transitions between the terminals of the device. The model is presented as a system of first order nonlinear differential equations with reference to voltages on parasitic capacitances between the transistor leads and algebraic coupling equations. The IGBT mathematical model in a resistive loaded circle is realized as Simulink model, which allows to investigate transients during switching of the transistor. Originality. Today, the question of the mathematical model working out, that takes into account the features of the switching of IGBT in the asynchronous electric drive, is not solved completely. In particular, during the simulation of a frequency controlled electric drive, the frequency converter is considered to be an ideal source of pulse voltage, or its characteris-tics are linearized and it is represented as a dynamic element of the second order. Also, power keys are often considered ideal. During the analysis of a frequency controlled electric drive, the motor is often considered as a symmetric ma-chine, but does not take into account asymmetry of supply voltage, that occurs when switching keys. In the work analyt-ical expressions for IGBT dynamic parasitic capacitances are calculated using partial derivatives of corresponding volt-ages on capacities from expressions that approximate the static dependencies of the parasitic capacitances of the device from the voltage between the collector and emitter and the dependencies is the catalog data. Practical value. The im-provement IGBT mathematical model will allow investigating the processes in power semiconductor converters, ana-lyzing their joint work with motor loading in normal and emergency modes, and developing the newest protection de-vices. Also, the use of such model makes it possible to conduct research of processes in the event of a fault or current leakage to the ground through the resistance of the human body in cables, which the motor connects to the converter, under different modes of neutral network operation. References 13, figures 3.
Authors and Affiliations
S. Vasylets, K. Vasylets
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