A scheme of restraining transformer inrush current based on control by switching voltage amplitude is proposed based on analyzing the influencing factors of transformer inrush current and deriving the mathematical relationship between inrush current and influencing factors. In this scheme

in order to make sure that the magnetic flux produced by the transformer no-load closing does not exceed saturated magnetic flux

the voltage amplitude should be controlled by selecting an appropriate curve

thus attaining the goal of restraining the transformer inrush current. The control function of voltage amplitude is derived from the magnetic flux inequality and the attenuation law of the transient flux component

and the upper and lower limitations of the initial value and slope in the voltage amplitude control function are deduced. The no-load closing process of a single-phase and three-phase transformer each in different conditions is simulated by using PSCAD/EMTDC

and the parameters such as magnetic flux

excitation inrush current and differential current are analyzed. The simulation results show that by controlling the voltage amplitude

the inrush currents can be restrained. Using this scheme

the value of inrush current can be kept in a small range to better overcome the influence of transformer inrush current. This work is supported by National Natural Science Foundation of China(No. 51377100)and Shandong Provincial Natural Science Foundation of China(No. ZR2013EEM029).