Are you interested in power electronics cooling?
Do you want to know how Simscape can
help you design and optimize the cooling system for a high power
inverter?
In this video, you will learn how
to use modeling and simulation to find
the most efficient heatsink for your liquid cooled inverter.
First, we will import device parameters from data sheets
into a Simscape Electrical model.
Then, we will use Detailed and Reduced Order models
iteratively to find the thermal steady-state faster
for different pump flow rates and heatsink choices.
Finally, we will compute the efficiency, coolant temperature,
and lifetime cost for different heat sink sizes.
Let's get started.
Let's have a look at the model.
We have a three phase inverter, driving a 30 kilowatts load.
The inverter converts the DC power
from the high voltage battery into three-phase AC power.
Conduction losses, switching losses, and reverse recovery
losses from the IGBTs and Body Diodes
generate heat in the case.
The case contains a heat exchanger.
Liquid coolant flows through the heat exchanger,
thanks to an electric pump system, absorbing the heat.
Then the coolant flows through a radiator, also called heatsink.
The heatsink fins dissipate the heat to the environment.
A fan blows air into the radiator
to increase dissipation.
To import datasheet parameters for the IGBTs and Body Diodes
in the detailed inverter model, use the Import
Device Parameters function.
For more information, visit the function documentation page.
Here are some plots of the IGBTs and Diode characteristics
and switching losses at different currents
and temperatures.
Now, we have a digital twin of our inverter,
ready to use for electrical and thermal simulations.
The inverter model contains two variants-- Detail and Reduced.
You can use the detailed inverter variant
to simulate the switching dynamics at high frequency.
The detail inverter variant consists
of six IGBT switching devices and the corresponding Body
Diodes.
You can use the getPowerLossSummary function
to generate a table with the conduction and switching
losses for the devices.
You can also use the getEfficiency function
to compute the system efficiency.
While the electrical dynamics are
in the order of milliseconds, due to the kHz switching,
the thermal dynamics are in the order of minutes.
If you're only interested in heat and temperature,
you can simulate faster by using the reduced-order model variant
to simulate the thermal dynamics without explicitly modeling
switching electrical dynamics.
You should set the simulation stop time to one hour
to observe the thermal steady state.
It is computationally intensive for a detailed model
to simulate these long-term studies.
You can use the detailed and reduced order models
iteratively to find the thermal steady-state faster.
Iteration looks like this.
Runs the detailed model to compute the accurate
losses on 4 AC cycles at a certain initial temperature,
setting stop time to 4/60 of a second.
Then, run the reduced model with these losses
to find the steady-state temperatures.
Finally, rerun this process with the new temperatures.
After three or four iterations, the temperatures
converge to the accurate steady-state values.
You can repeat this process for multiple heatsink sizes
to find the optimal heatsink that maximizes inverter
efficiency and minimizes cost.
In this case, the inverter efficiency
increases with larger and larger heatsinks
as the coolant temperature decreases, but with diminishing
returns, as the efficiency increases do not
compensate for the larger heatsink cost, eventually.
For this inverter, it seems that a heat sink of around 120 fins
combines a good blend of efficiency and lifetime cost.
Here's a visualization of how that sink would look like.
I hope this was helpful.
To summarize, we imported device parameters,
ran detail and reduced other models
to find steady state temperatures,
and computed the optimal size of the radiator
for a high-power three-phase inverter.
To learn more, please check the MATLAB and Simscape
documentation.
Thanks for watching.