There are numerous ways to convert single phase to three phase system. The main are as follows:
1- Three phases alternators fed from single phase voltage sources where special windings and connections to be provided.
2- Conversion with passive elements like capacitors and inductors which is hard to tuff work
3- Power electronics elements: to convert from AC to DC, then convert DC to three phase AC system (power quality to be watched carefully)
One can refer to the following reference: