A waste heat recovery system including at least two integrated rankine cycle systems (12, 14), the recovery system comprising: a heat generation system comprising at least two separate heat sources having different temperatures; a first rankine cycle system comprising a first expander, wherein the first rankine cycle system is coupled to a first heat source among the at least two separate heat sources and configured to circulate a first working fluid; wherein the first rankine system is configured to remove heat from the first heat source; a second rankine cycle system comprising a second expander and a condenser; wherein the second rankine cycle system is coupled to at least one second heat source among the at least two separate heat sources and configured to circulate a second working fluid, the at least one second heat source comprising a lower temperature heat source than the first heat source, wherein the second rankine cycle system is configured to remove heat from the at least one second heat source; a cascaded heat exchange unit, wherein the first and second working fluids are circulatable in heat exchange relationship through the cascaded heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system; characterized in that the waste heat recovery system further comprises: a partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit; a pump situated between the condenser and the partial evaporator; and a first control valve situated in a by-pass path between the condenser and the partial evaporator, wherein the at least one second heat source is configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit in a cycle of the second rankine cycle system. a heat generation system comprising at least two separate heat sources having different temperatures; a first rankine cycle system comprising a first expander, wherein the first rankine cycle system is coupled to a first heat source among the at least two separate heat sources and configured to circulate a first working fluid; wherein the first rankine system is configured to remove heat from the first heat source; a second rankine cycle system comprising a second expander and a condenser; wherein the second rankine cycle system is coupled to at least one second heat source among the at least two separate heat sources and configured to circulate a second working fluid, the at least one second heat source comprising a lower temperature heat source than the first heat source, wherein the second rankine cycle system is configured to remove heat from the at least one second heat source; a cascaded heat exchange unit, wherein the first and second working fluids are circulatable in heat exchange relationship through the cascaded heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system; characterized in that the waste heat recovery system further comprises: a partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit; a pump situated between the condenser and the partial evaporator; and a first control valve situated in a by-pass path between the condenser and the partial evaporator, a partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit; a pump situated between the condenser and the partial evaporator; and a first control valve situated in a by-pass path between the condenser and the partial evaporator, wherein the at least one second heat source is configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit in a cycle of the second rankine cycle system.