Impedance Measurement for a complex circuit

1) How can I use the block impedance measurement? I cannot connect it to my Simscape circuit and there are no examples in the help.

2) How can I use Simscape and not the Specialized Power System tools to do the same?

Answer 1

[MathWorks Support Team]

1) The 'Impedance Measurement' block does not directly connect with Simscape language based blocks as it is from the Specialized Power Systems library. Elements from this library are implemented as Simulink blocks and not directly compatible with Simscape language blocks.

When modeling with the SPS library, you can using the 'powergui' block to measure the impedance. In 'powergui', browse to the ‘Tools>>Impedance measurement’ option. You then need to connect the 'Impedance measurement’ block across the load you would like to measure. You can then select your desired options/settings to view the ‘Impedance Vs Frequency’ graph and load the data to workspace. 

Here is an example from the documentation illustrating this approach: 

https://www.mathworks.com/help/sps/ug/steady-state-analysis-of-a-linear-circuit.html

2) To find the impedance of a complex circuit with Simscape Electrical blocks with RLC, another workaround would be to represent the following mathematical equation in Simulink and then extracting the impedance:

Z = R+j*X = Phasor_V / Phasor_I = |V|/|I| * exp(j*(Vang - Iang))
=  |V|/|I| * ( cos(Vang - Iang) +1j*sin(Vang - Iang) )
Phasor_V = |V|exp(j*Vang)
Phasor_I = |I|exp(j*Iang)

Set the initial conditions of the denominator i.e. the current to a small value so that you do not end up with a 'x/0' condition. Thus the actual output would begin after the initial condition has ended. Attached is a model that represents the above equation in Simulink.