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ReliPE

Work packages

 

WP1: Provide reference components and topologies

Objective: Electrical and thermal dynamic models will be developed for numerical as well as for real time simulation of temperature stress conditions of the component hot-spot areas. A set of representative converter topologies and semiconductor components for high voltage power conversion will be provided. By case studies, the provided tools will be demonstrated by assessing thermal stress and efficiency for the relevant high voltage converter topologies depending on operation modes.

WP highlights (May 2017): 

  • Providing accurate thermal models for 1000A/3300V IGBT test objects (ref. WP4) for case simulations.
    • By FEM simulations and by experiments.
    • Including cross-coping effects between IGBT chips and free-wheeling diode chips. 
  • Developed thermal electrical simulation models (Simulink) for two MMC topology variants, and test simulations.

WP2: Evaluation of lifetime test methods

Objective: To provide lifetime models that are applicable for real high voltage converter applications based on prevailing models used for accelerated testing. Furthermore to contribute towards standardization of semiconductor lifetime test methods.

WP highlights (May 2017):

  • Review of existing life time test methods regarding their applicability for the converter normal operation modes
    • Decided to elaborate two published models, especially focusing formula validity for low ΔT (temperature swings) of hot-spots
    • Decided to investigating correlations between stress conditions such as between high and low ΔT 
  • Processing results from the  WP4 IGBT test programs and inputs to continuing experiments.
    • Initial model valuation based on two power cycling test runs; One high and one low temperature swing of IGBT junction temperature

WP3: Ruggedness of IGBTs

Objective: To contribute towards development of robust components aiming to reduce downtime of high voltage converters. Primary focus is aimed at obtaining a stable behavior during and after fault conditions. The WP will mainly be processed by a PhD scholarship hosted by the research partner TU Chemnitz.

WP highlights (May 2017):

  • PhD work on analysis of fault ruggedness of IGBT
    • Interim FEM simulations of effects from thickness of emitter metallization 
  • Provide test equipment for short circuit experiments
      • A 6kV double pulse short circuit tester constructed and commissioned 
  • Experimental work on short circuit ruggedness
      • Provided special test objects for ruggedness experiments

WP4: Accelerated lifetime experiments

Objective: To support the development of improved lifetime models for IGBT devices by accomplishing a power cycling lifetime test program applying representative commercial high power IGBT test objects. Furthermore, to adapt the models for representing the new and more rugged components coming into the market.

WP highlights (May 2017):

  • Power cycling of 1800A/4500V commercial press-pack type IGBTs
      • Accomplished test to clarify root cause for the early failures experienced with these test objects in the previous OPE project 
  • Test program for validation of power cycling lifetime formulas
      • A number of 50 1000A/3300V IGBT modules provided for the first phase of the power cycling test program.
      • 1st test run (ΔT=70, Tjmin=60) completed
      • 2nd test run (ΔT=40, Tjmin=60) started March 2017
  • Thermal impedance (Zth) characterization of the 1000A/3300V test objects for input to WP1
      • Including thermal crosstalk between IGBT and free-wheeling diodes chips
      • A separate control and monitoring hw/sw for the Zth validation under construction

WP5: Real-time condition monitoring and prediction 

Objective: To exploit results achieved in WP1, WP2 and WP4 for development of a methodology for online estimation of present component status and of remaining lifetime or time to repair. Secondly, the methodology should be able to detect abnormal operation conditions and give early warning of failures.

WP highlights (May 2017):

  • Reassessing methodologies examined in the previous research (OPE project)
      • The validity of applying Miners rule is found to be questionable due to mutuality between different stress conditions levels
      • Inputs to the WP4 test program for special investigations like regarding correlations between different stress conditions
  • Dynamic real-time estimation of IGBT hot-spot temperature conditions (semiconductor chips) based on dynamic models for thermal impedances
      • Implementing a 1st approach by applying National Instruments hw/sw tools
      • 1st approach assuming only conduction losses
      • A mix of monitoring and calculating variables
      • 2nd approach to include switching losses  
  • Other methodologies as references for own investigations
      • Provided a commercial driver system for reference measurements 
  • Methods for real-time power cycling accumulation and sorting
      • Initial works
      • Algorithms for power cycling counting
      • Assuming dynamic online estimation of semiconductor hot-spot temperature conditions 
  • Methods for online estimation of remaining lifetime based on accumulated history
      • Detailed planning following outcome from abovementioned highlights

WP6: Contribution to education

The objective of this WP is to strengthen the education of applied power electronics at NTNU on topics related to reliability of power semiconductors. Furthermore, to provide post-experience courses for researchers and engineers.

WP highlights (May 2017):

  • A two year PostDoc position at NTNU
    • Employment under processing, assumed startup mid 2017
    • Topics within methods for failure detection, condition monitoring and lifetime prediction of power semiconductors
  • Student projects NTNU
    • SINTEF offering topics for student specialization project and master project
    • Co-supervisors by SINTEF staff
    • In 2016-2017 a student specialization project and master project on assessment of accelerated life time test methods used for IGBTs, and applicability for Silicon Carbide devices 
  • Student exchange SINTEF/NTNU and TU Chemnitz 
    • Topics from planned ReliPE Work Packages
    • TU Chemnitz internship students visiting SINTEF/NTNU; Supervised by SINTEF staff
    • NTNU student visiting TU Chemnitz; Supervised by TU Chemnitz staff
    • In 2017 two TU Chemnitz students are at SINTEF for six month internships