There are a couple of algebraic loops that need to be resolved in your model. First, in the Boost w/converter subsystem, the signal being converted to type double is used as part of the circuit used for in the ‘PS-Simulink Converter 1’ block.
Second, in the ‘Buck w/ converter’ subsystem has a dependency to the output signal of the ‘U_bar’ block. ‘MOSFET 1’ uses this signal, which is part of the circuit used for the ‘PS-Simulink Converter 1’ block.
Other problems that cause this error are discontinuities used in the model, for example, the ‘Relational Operator’ block.
For more information regarding Algebraic Loops and how to fix them, check out the following link: http://www.mathworks.com/help/simulink/ug/algebraic-loops.html
