Tie variable X to a definite value, for example by connecting an appropriate domain reference block.

I have the circuit in this figure:

I get the following error: Initial conditions solve failed to converge. Nonlinear solver: Linear Algebra error. Failed to solve using iteration matrix. The model may not give enough information to make it possible to solve for values of some of its variables. Specific advice is given below.

all components and nodal across variables involved Tie variable x to a definite value, for example by connecting an appropriate domain reference block.

I have looked at the other questions on this on MATLAB answers and these solutions did not work: Changing the S-PS block to filter input.

One question was missing ground but I have that.

Any idea what is wrong?

Answer 1

[nick]

Hi Leah,

I understand from your query that you want help in resolving the error “Initial conditions fail to converge”

I have recreated the circuit in Simulink using the R2023a version on my end. Upon examining your circuit, it appears that the differential voltage at the op-amp inputs is Vin*R2/(R1 + R2). The “op-amp” block used in the model is an ideal op-amp having infinite differential gain, and since the circuit lacks feedback, the output tends to go to infinity. This is likely what's causing the issue with the initial conditions not converging.

You may refer to the following documentation to learn more about differential op-amp : https://www.mathworks.com/help/simscape/ref/opamp.html

Hope this helps,

Regards,

Neelanshu