Mutual inductance identification method and mutual inductance calculation device using same

A mutual inductance calculation device for a wireless power transmission system, the wireless power transmission system comprising a primary circuit, a resonant cavity and a secondary circuit, the mutual inductance calculation device comprising:

• a sampling circuit for sampling a primary resonant current of the primary circuit and sampling a secondary resonant current and a secondary resonant voltage of the secondary circuit;
• a first filtering circuit configured to filter the primary resonant current, the secondary resonant current and the secondary resonant voltage respectively to obtain a first harmonic component and a second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage, wherein a frequency of the first harmonic component and a frequency of the second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage are different;
• an analog switch configured to modulate the first harmonic component and the second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage respectively;
• a second filtering circuit configured to demodulate the modulated first harmonic component and the modulated second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage respectively;
• and
• a micro control unit configured to obtain an amplitude of the first harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage and a phase difference between the first harmonic component in the secondary resonant voltage and the first harmonic component in the secondary resonant current according to the demodulated first harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage, obtain an amplitude of the second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage and a phase difference between the second harmonic component in the secondary resonant voltage and the second harmonic component in the secondary resonant current according to the demodulated second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage, calculate a mutual inductance parameter between the primary circuit and the secondary circuit according to the amplitude of the first harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage, the amplitude of the second harmonic component in each of the primary resonant current, the secondary resonant current and the secondary resonant voltage, the phase difference between the first harmonic component in the secondary resonant voltage and the first harmonic component in the secondary resonant current and the phase difference between the second harmonic component in the secondary resonant voltage and the second harmonic component in the secondary resonant current.