This really simple schematic shows how to do DC sweeps in Qucs.

Qucs does not provide a "DC Simulation" object that matches SPICE's (or Xyce's). Instead, you add a "DC Simulation" object that has almost no parameters of any value to us, and a second "Parameter Sweep" object. The "Sim" parameter of this parameter sweep object should be the name of the DC Simulation object you placed (you choose it from a drop-down menu, so it's easy to select).

Then you use the name of the voltage source you want to sweep over in the "Param" parameter of the sweep.

Put the start, stop, and number of points into the appropriate boxes.

There was a bug in versions of qucs-s up to 0.0.20

This demo works as intended in version 0.0.21 of qucs-s. However, there was a bug in the netlist generation step of previous versions of qucs-s for parameter sweeps, documented in https://github.com/ra3xdh/qucs_s/issues/8. While the dialog box for setting up the parameter sweep object correctly computes the step size from the number of points, or the number of points from the step size, there is an off-by-one error in the netlist generation stage which incorrectly computes the parameter sweep step from the number of points chosen.

If you are a version of qucs-s older than 0.0.21, you will have to modify the parameter sweep to get it to generate a netlist that takes the intended number of steps. Ignore the "step" value in the parameter sweep dialog, as Qucs-s doesn't use it to generate the netlist, and will compute the step from (stop-start)/points instead of (stop-start)/(points-1). Therefore, you need to set "Number" in the dialog to one fewer point than you actually want in order to get the netlist generation correct. In this demo, we want to sweep V1 from 0 to 5 in steps of .5, which would normally be 11 steps (0.0, 0.5, 1.0, 1.5, ... 4.5, 5.0), but you can see in the schematic that we use Points=10 instead.

Xyce and SPICE support DC lines that Qucs schematics don't do natively

Qucs does NOT have any way to generate netlists with multi-parameter DC sweeps of the form:

.DC V1 1 2 3 V2 4 5 6

Further, Xyce does not support having more than one .DC line in a netlist, so if you need to do nested DC sweeps like this, you must do it in an "Xyce Script," which allows you to hand-code the analysis and print statements instead of using Qucs-s components to generate them.

Exported schematic image