Method for detecting foreign material, and apparatus and system therefor

A power reception method for a wireless power receiver, the power reception method comprising:

• storing information on a reference quality factor and a reference peak frequency;
• generating a foreign object detection (FOD) status packet including the information on the reference quality factor and the reference peak frequency;
• transmitting the FOD status packet to a wireless power transmitter;
• receiving a foreign object detection indicator indicating whether a foreign object is present in a charging area of the wireless power transmitter in response to the FOD status packet,
• wherein the FOD status packet has a length of two bytes,
• wherein one byte of the FOD status packet includes a six-bit reservation field and a two-bit mode field, and
• wherein all bits of the reservation field are recorded as zero;
• and
• performing a wireless charging procedure with a first power when the foreign object detection indicator indicates that the foreign object is not present in the charging area.