Statistical Method of Estimating Semiconductor Switching Transition Time enabling Condition Monitoring of Megawatt Converters

Detection of Insulated Gate Bipolar Transistor (IGBT) switching transition time (ttr) is a promising Temperature Sensitive Electrical Parameter (TSEP) for condition monitoring of IGBT power modules in converters for wind turbines. The accuracy required on ttr detection is in nano seconds, which typically requires precision timing circuitry, or Analog to Digital Conversion (ADC) rates in hundreds of Mega Samples Per Second (MSPS). A method on calculating the statistically estimated switching transition time (t̂tr) is proposed in this paper. During multiple switching transitions of an IGBT, the IGBT collector-emitter voltage (vce) may be sampled with sample rates in sub MSPS rates, yet with statistical accuracy on estimated t̂tr in nano seconds. A stand alone Converter Monitoring Unit (CMU) which samples vce and IGBT current (ic), was mounted in the converter of a multi Mega Watt (MW) field test wind turbine. The proposed method is validated by testing it on field data from the CMU and by testing it on synthetically generated data. The proposed method is an enabler for low-cost monitoring of converters for wind turbine field applications.