1. A method for identifying equation-level errors in a system model used in circuit simulation, comprising: providing a representation of the structure of a system model to be simulated, the system model including a plurality of system model components; converting the representation of the structure of the system model to a plurality of numerical equations, each numerical equation corresponding to a system model component or a topology equation for the system model; and identifying at least one illegal configuration in the system model by performing a numerical analysis of at least one of the numerical equations.