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Condition Monitoring for Power Electronics Reliability (COMPERE). Shaoyong Yang Angus Bryant Phil Mawby July 18 th 2008. 1. Progress since last ESR meeting. 1. literature survey: a review paper drafted as part I. Questionnaire: a report based on 56 responses; a paper being drafted.
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Condition Monitoring for Power Electronics Reliability (COMPERE) Shaoyong Yang Angus Bryant Phil Mawby July 18th 2008 1
Progress since last ESR meeting 1. literature survey: a review paper drafted as part I. • Questionnaire: a report based on 56 responses; a paper being drafted. • A webpage for COMPERE http://www2.warwick.ac.uk/fac/sci/eng/eed/research/peater/research/compere • Simulation work plan ready for discussion. • Preliminary simulation with power device thermal models in Matlab/Simulink & Saber. • Others: ECPE workshop in Toulouse, 25-26 June LSA/MSA workshop at Aston University, 10 July 2
Simulation work plan • Select a model (done) • A control programme in plecs (tried). heat sink + packaging to be considered. • A lifetime interpreter. 3
Saber thermal models • Dynamic model, IRG families all encrypted. • IGBT self-heat (based on Hefner’s several papers). Assumptions, e.g., linear drift charge less accurate. • Saber model can only work as a comparison! 4
Matlab/simulink model (1) • Compact modelling of IGBTs and diodes. • Angus and Phil developed. • Integrated device optimisation & parameter extraction. • Proven for a wide range of conditions. • Full temperature dependency, –150°C to +150°C. • Excess carrier density modelled: • Critical to on-state and switching behaviour. • Ambipolar diffusion equation (ADE) describes carrier distribution. • Fourier series used to solve ADE. • Boundary conditions set by depletion layers, MOS channel, emitter recombination, etc. 5
Matlab/simulink model (2) • Excess carrier density (stored charge) is one-dimensional for 90% of CSR. • Fourier series solves 1D carrier density p(x,t) in CSR: • Fourier terms pk(t) solved by ordinary differential equations • Boundary conditions: CSR edges x1,x2 and gradients dp/dx (set by currents). • Depletion layer voltage Vd2 provides feedback to keep p(x2)=0. • Classic MOS model used to determine e- current In2. 6
Matlab/simulink model (3) Base region resistance (conductivity modulation) Emitter recombination (injection) Carrier storage region (CSR) with Fourier series solution Depletion layer equations Classic MOSFET model Miller capacitance Kelvin emitter inductance 7
Simulation work • Parameterisation of models using a chopper cell. • Look-up table (LUT) generation file (2b delivered) • If (V, I) belongs to the LUT, use it; • Otherwise re-run and generate it. • Parameterisation of heat-sink using an inverter leg (2b delivered) . Converter simulation Simulation controller Look-uptable EXTERNAL CONDITIONS LOSS DATA Device temp. Power diss. Heatsink model Compact models System modelling Device modelling 8
Parameterisation of power devices (1) • Parameterise power devices using the chopper cell circuit - Initial fit by hand - All parasitics required (esp Ls) - C&R: use if necessary; otherwise C=100pF,R=100Ohm. - Switching and on-state matching to parameterise devices. 9
Power converter modelling (1) • Look-up table: • - Generated from device models. • - Gives losses as a function of load current and temperature. • - Simple converter/heatsink model simulates device temperature. • - Rapid and accurate estimation of device temperature for whole load cycle. 12
Power converter modelling (2) • Plecs: combined electrical and thermal simulation of power electronic systems in Simulink • Power devices like simulink models, but with thermal info, e.g., diode: Vf, Ron, Thermal (Pon,Poff,Pcon,Rth, Cth) 13
Full system simulation • Standard Federal Urban Driving Schedule. • Simple drive model gives inverter electrical conditions. • Resulting IGBT temperature profile plotted in relation to the vehicle speed. • Peaks in temperature correspond to acceleration/deceleration. 14
Thermal mechanical model Stress-strain plot Rth variation model 15
Experimental work • Thermal cycling • An environmental chamber to add thermal stress on devices. include new, ageing and partly faulted ones. • Passive tests may be tried to study the solder fatigue. • 2. Power cycling tests (PCT) • To check the bond wire lift-off (VCE,sat) • + solder fatigue (Rth) • Issues: • To obtain test samples and borrow industrial expertises. • To discuss with Durham on the test conditions for PCTs. 16
Future work • A target system as a benchmark • Clarify topologies, power ratings and work conditions • Select target devices and parameterise them. • Carry out converter simulations. • Development of thermo-mechanical model • Further literatures. Any test information? • 3. Experimental work to be carried out • First to parameterise the power devices, and then to study the packaging reliability. 17