The main subject of this work is the analysis of the both main ways of regulation of the rankine cycle used in thermal power plants based in steam cycle. The work is divided in three main parts. The first one is theoretical, and in it, is introduced the rankine cycle, the ideal and real, and different improves of it. The second is theoretical too, and it is about the different types of regulation and how they work. And finally the third part is practical one, in it the start point is a rankine cycle used in a plant working at nominal load. Then the both, nozzle and throttle governing are calculated with two different mass flow than nominal flow. In this part is also calculated the efficiency of the control stage of the turbine used in the nozzle regulation.