Help: Inverter loss simulation result different from test

[jeffwjz]

I have been working on an inverter loss simulation in Simulink, the module I used is a universal bridge with 3 legs. The inverter parameters (eg. forward voltage drop, on resistance) are obtained from manufacturer datasheet.

Two methods are used. The first method is to fetch DC link voltage/current and inverter output voltage/current to calculate power difference in Simulink. The difference is regarded as inverter loss.

The second method is direct calculation. Currents in each igbt/diode pair are measured in simulation. The switching loss is obtained by the on/off switching loss energy diagrams from datasheet at each on/off instant, and averaged over time. The conduction loss is straightforward and calculated from current in components, forward voltage drop and on resistance.

Then the simulation results are compared with test. It appears that the two simulation results are different from each other, also they are both much lower than measured in lab. The actual inverter loss measured in test is by measuring the power difference between inverter input and output.

I am wondering what caused the difference of the 3 methods, at least I think the two simulation methods should give same results. Is there anything else I should consider?

Thanks.

 

[FvM]

Can you give an idea about the range of observed differences?

Regarding the difference between simulations, a simple explanation would be that the Simulink IGBT model behaviour differs from datasheet specification. You can further differentiate the simulation results to see where it is.

Regarding real hardware behaviour, differences are likely to observe. You would need to measure IGBT current and voltage waveforms during switching, calculate on-state and switching loss energies and try to locate the differences.

 

[jeffwjz]

Can you give an idea about the range of observed differences?

Regarding the difference between simulations, a simple explanation would be that the Simulink IGBT model behaviour differs from datasheet specification. You can further differentiate the simulation results to see where it is.

Regarding real hardware behaviour, differences are likely to observe. You would need to measure IGBT current and voltage waveforms during switching, calculate on-state and switching loss energies and try to locate the differences.

Thank you very much, the input DC power is around 100kw. A inverter power loss difference of 1kw between simulation and test is observed. The purpose of the test is for comparing the inverter losses of different modulation methods.

The simulation does perform a similar amount of loss reduction between new and old methods compared with test, but it seems that the total loss simulated is less than tested.