Converter, power transmission system, and controller

A converter includes: a terminal that receives code-modulated power into which first alternating-current power has been code-modulated with a modulation code; and a circuit that converts the code-modulated power with a conversion code to generate second alternating-current power. The conversion code is based on the modulation code. A frequency of the second alternating-current power is higher than a frequency of the first alternating-current power.