Voltage scaling is one of the prominent power saving approaches in Xilinx® devices. There are different voltage rails to supply specific voltages to logic in the device. Each Device Data Sheet lists the recommended operating conditions of these rails. For example, Kintex®-7 devices can operate with a VCCINT rail between 0.97V and 1.03V. You can make use of voltage scaling to meet your power budget. In the Hardware setup, these rails are supplied by external Power Regulators with fine-grained controls. Because power increases when supply voltage increases, you must provide the exact supply voltage to estimate power accurately.
To specify power supply voltages in the Vivado® Integrated Design Environment, enter the values in the Power Supply tab of the Report Power dialog box.
set_operating_conditions -voltage {vccint 0.98 vccaux 1.8}