The present technology relates to a power supply control device, a method of controlling the same, and a power supply control system that enable easy device registration. A power control server outputs power through a power line, outputs a high-frequency signal and communicates with an electronic device to which the power is output, through the power line, and reads out device information including at least identification information that identifies the electronic device, obtains user information related to a user who uses the electronic device, and transmits the obtained user information and the read out device information to an information management server. The information management server receives the user information and the device information transmitted from the power control server, and performs user registration related to the electronic device identified by the identification information included in the device information, based on the received user information. The present technology can be applied to a power supply control system that supplies the power to an electronic device, for example.