There are occasions when one is interested in the "steady-state" behaviour of a circuit with periodic inputs and not so much in how it got there. This is particularly true of many power electronic circuits. We can, of course, perform transient simulation until steady state is reached, thus obtaining the steady-state behaviour at the end. However, it may take a long time to reach the steady state. This problem has been realized very early, and methods have been developed to compute the steady-state solution without going through a long transient simulation. Unfortunately, these techniques have not been implemented in most of the general-purpose circuit simulators.

SEQUEL offers the option of efficient SSW computation to the user. The computation techniques implemented in SEQUEL for this purpose are described in Ref. [1]-[4] and the SEQUEL manual.

The following table illustrates the dramatic saving in computation time that results when the SSW method is used. In these examples, N1 indicates the number of cycles required to reach the steady state by transient simulation, and N2 is the number of Newton-Raphson iterations in the SSW method (which is equivalent to that many cycles of transient simulation).

Example	N1	N2	Circuit file
Buck Converter	750	4	buck.in
Boost Converter	625	3	boost.in
Cuk Converter	1250	3	cuk.in
1-phase half-wave rectifier	150	3	halfwave.in
1-phase half-controlled bridge converter	110	4	conv1.in
3-phase diode bridge rectifier	200	4	rect3p.in
Induction motor problem	125	17	imssw.in

References

1. T. J. Aprille and T. N. Trick, "Steady-state analysis of nonlinear circuits with periodic inputs," Proc. IEEE, vol. 60, pp. 108-114, 1972.
2. T. J. Aprille and T. N. Trick, "A computer algorithm to determine the steady-state response of nonlinear oscillators," IEEE Trans. Circuit Theory, vol. 19, pp. 354-360, 1972.
3. F. R. Colon and T. N. Trick, "Fast periodic steady-state analysis for large-signal electronic circuits," IEEE J. Solid-State Circuits, vol. 8, pp. 260-269, 1973.
4. T. N. Trick, F. R. Colon, and S. P. Fan, "Computation of capacitor voltage and inductor current sensitivities with respect to initial conditions for the steady-state analysis of nonlinear periodic circuits," IEEE Trans. Circuits and Systems, vol. 22, pp. 391-396, 1975.