A method of controlling a wireless power receiver. The method includes receiving, by a power receiver, power from a wireless power transmitter; receiving, from the wireless power transmitter, a time set value that is set for checking cross connection; in response to receiving the time set value, generating a power variation in the wireless power receiver by converting a load status from a first load status to a second load status; and maintaining the second load status for a time corresponding to the received time set value.