System and method for actively controlling output voltage of a wireless power transfer system

A wireless power transfer system comprising:

• a first converting unit operable at a constant operating frequency and configured to convert a first DC voltage of an input power to a first AC voltage;
• a contactless power transfer unit coupled to the first converting unit and configured to transmit the input power having the first AC voltage, wherein the contactless power transfer unit comprises at least a first power exchange coil and a second power exchange coil magnetically coupled to each other and operable at a resonant frequency;
• a second converting unit coupled to the contactless power transfer unit and configured to receive a power having a second AC voltage corresponding to the first AC voltage from the contactless power transfer unit, convert the second AC voltage of the received power to a second DC voltage, and transmit the power having the second DC voltage to an electric load;
• and
• an active voltage tuning unit coupled to the contactless power transfer unit and configured to control the second DC voltage based on a difference between the second DC voltage and a reference voltage and at least one among a difference between the resonant frequency and the constant operating frequency and a difference between a phase angle of the first AC voltage and a phase angle of an AC current.