Hi My friend
It depends on the technology that manufacturer preferred . for example for welding system , maximum authorized voltage is around 60 volts , but current is high ( up to 1KA ) . you can achieve it with a simple H Bridge with powerful IGBTs . but UPS out put voltage is around 220 volts ( in my country phase voltage is around 220 volts ) . if you want know about them , you should start to reading about power electronics and SMPS design . if you want i can introduce you some good books .
Best Wishes
Goldsmith