Wireless power transmission device and power transfer system

A power transfer system comprising:

• a power transmission device;
• and
• a power reception device configured to wirelessly receive power from the power transmission device,
• the power transmission device including
• a power transmitter configured to wirelessly transmit power to the power reception device,
• an inverter configured to generate power at a prescribed frequency and output the generated power to the power transmitter,
• a loss detector configured to detect power loss, and
• a controller configured to control output power from the inverter,
• the controller being configured to carry out
• power control for converging magnitude of the output power to target power, and
• frequency control for converging a frequency of the output power to an optimal frequency at which power loss detected by the loss detector is minimized,
• the controller being configured to
• stop the frequency control and perform only the power control for a prescribed second period when magnitude of the output power does not converge and a frequency of the output power does not converge in the power control and the frequency control carried out for a prescribed first period,
• determine that a condition for the frequency control is inappropriate when magnitude of the output power has converged after lapse of the second period, and
• determine that a condition for the power control is inappropriate when magnitude of the output power does not converge after lapse of the second period.