Missing a continuous variable resistor for Specialized Power Systems

Hi,

I am currently working on a system where I would like to test varying resistance values during the simulation to see how the control would react. Initially I tried to use a variable resistor but I have created my system for continuous time and specialized power systems only has a discrete variable resistor block.

Is there a way to accomplish what I'm looking for? I have seen variable resistors in other libraries such as Simscape / Foundation Library / Electrical / Electrical Elements and RF Blockset / Circuit Envelope / Elements, I am relatively new to simscape electrical and I'm unsure if theres a way to connect these blocks into my system or if there's another workaround.

Any help would be greatly appreciated. Thank you

Answer 1

[Sumukh]

Hi Thomas.

There is no “Continuous” simulation-type “Variable Resistor” block available in Simscape Specialized Power Systems (SPS) library. The “Variable Resistor” block in SPS can only run when the “Simulation Type” is set to “Discrete” in the “powergui” block, as per the following documentation:

https://www.mathworks.com/help/releases/R2023a/sps/powersys/ref/variableresistor.html#:~:text=Simulation%20type%20to-,Discrete,-and%20select%20the

However, if it is required to vary the resistance based on a non-linear relationship between the voltage and current, custom blocks can be created. The newly created block can be used in “Continuous” mode of simulation. You can refer to the following documentation to know more about creating a custom non-linear resistor block:

https://www.mathworks.com/help/releases/R2023a/sps/powersys/ug/building-and-customizing-nonlinear-models.html#f1-7986

A possible workaround is to model the entire system using Simscape Electrical blocks, to use the “Variable Resistor” available in Simscape Electrical library. You can follow this documentation to know more about the same:

https://www.mathworks.com/help/releases/R2023a/simscape/ref/variableresistor.html

The Simscape Electrical network is modelled in the same way as the network made of Simulink SPS blocks, along with the “Solver Configuration” block attached to the model, to configure the solver for the Simscape network. The blocks also have “Initial Targets” tab in the block parameters to specify initial conditions.

I hope this helps resolve your issue.