How to get information about formulas used in getPowerLossSummary function?

I wanted to count losses in my Simscape Electrical DCDC-buck model. After getting value of dissipated power i asked myself. How it was counted. Unfortunately getPowerLossSummary function is inside .p file.

Answer 1

[David John]

Individual blocks in Simscape Electrical track their own losses via an internal power_dissipated variable. For many blocks, this is calculated just based on any terms that are lossy in the equations describing the block. For example, an ideal capacitor has no intrinsic loss, while an ideal capacitor with a series resistance does. Similarly, a MOSFET has a lossy Rds,on...and there are also losses when you switch the MOSFET on with an applied Vds (because the charge on Coss gets discharged through the channel resistance).

The getPowerLossSummary function simply looks inside all of the blocks in your model and extracts the values of all of the power_dissipated variables and adds them up. If you have blocks without this variable, the function will not report any loss for that block.

Note that this feature is only supported for certain Simscape Electrical blocks. It is not supported for blocks from the Foundation Library.

Answer 2

[Tomasz Filipiak]

I created plots od power dissipated using function ee_getPowerLossTimeSeries and compare them with power counted as product of I_D and V_DS. As we can see they are different. When I used also pe_getPowerLossSummary and count {trapz(time,Pd)/Tsimulation} and I got same answers. This function makes transfer of power or is it only an accident?

[David John]

Power counted as a product of I_D and V_DS gives the instantaneous power (both the reactive and dissipative parts). The reactive part is not lossy overall. When you take the average of I_D*V_DS, you obtain only the lossy part and this is what getPowerLossSummary should report. If I understand your message correctly, it looks like that is indeed what you see...instantaneous power is different (because it includes the reactive part) and average power is the same (that is the lossy part by itself).

The getPowerLossTimeSeries and getPowerLossSummary (whether ee_* or pe_* or elec_*) all do the same thing. The different names are to provide backwards compatibility for users who used Simscape Electronics or Simscape Power Systems before those were merged into the single product: Simscape Electrical.

[Tomasz Filipiak]

'Power counted as a product of I_D and V_DS gives the instantaneous power (both the reactive and dissipative parts).' Sorry I didnt mention it but the red one is what i got from getPowerLossTimeSeries and a green plot is power counted as a product of I_D and V_DS. So if instantaneous power has reactive and dissipative part, power from getPowerLossTimeSeries only dissipative, why is it sometimes bigger that counted?