The Algebraic loop warning

Block diagram 'FVModeli' contains 1 algebraic loop(s). To see more details about the loops use the command Simulink.BlockDiagram.getAlgebraicLoops('FVModeli') or the command line Simulink debugger by typing sldebug('FVModeli') in the MATLAB command window. To eliminate this message, set Algebraic loop to "none".

Component:Simulink | Category:Block diagram warning

Found algebraic loop containing:

FVModeli/PV /Ipv/Fcn1

FVModeli/PV /Ipv/Fcn

FVModeli/PV /Ipv/RS (algebraic variable)

Component:Simulink | Category:Model

An error occurred while running the simulation and the simulation was terminated

Caused by:

Simulink cannot solve the algebraic loop containing 'FVModeli/PV /Ipv/Fcn1' at time 0.1 using the TrustRegion-based algorithm due to one of the following reasons: the model is ill-defined i.e., the system equations do not have a solution; or the nonlinear equation solver failed to converge due to numerical issues.

To rule out solver convergence as the cause of this error, follow either of the suggested actions. If the error persists in spite of the above changes, then the model is likely ill-defined and requires modification.

Suggested Actions

Switch to LineSearch-based algorithm using

set_param('FVModeli','AlgebraicLoopSolver','LineSearch') FİX

Reduce the RelTol parameter so that the solver takes smaller time steps. OPEN

[Sulaymon Eshkabilov]

u(2) has such a small value 10^-19 ?

Answer 1

[Kiran Felix Robert]

Hello Elif,

Refer the Algebraic Loop Documentation for an initial understanding about Simulink algebraic loops.

In your block diagram, there are two instances of algebraic loops

1. Output of ‘Fcn’ block through the ‘Gain Block – RS’ to the ‘Input-6 of top Bus’
2. Output of ‘Fcn’ block through the ‘Gain Block – RS’ to the ‘input-1 of bottom bus’ through the ‘Bottom Fcn’ block and to the ‘Input-7 of top Bus’

Refer the answer here for a more detailed information and some ways of resolving the error.

Kiran Felix Robert