If you are an individual learner or a student, trying to hunt down version 11.1.3 is likely more trouble than it is worth. Powersim offers a of their current software that is fully functional for learning purposes (with circuit size limits).

Common issues with PSIM 11.1.3 include:

PSIM (Power Simulation) stands out because it is built specifically for power electronics rather than general-purpose analog circuits. Version 11.1.3 includes: Download PSIM by Powersim, Inc.