Dynamic Performance Improvement Method for Buck Converters With Small Input Capacitors in WPT Systems Based on Voltage Feedforward Active Damping Control

In wireless power transfer (WPT) systems, a right-half-plane zero (RHPz) will be indicated in the receiver Buck converter's control-to-output transfer function when the receiving end uses a compensating network with current source characteristics. The transient performance of the system is seriously impacted by the presence of the RHPz, particularly when the RHPz is situated near the origin. Recent research has demonstrated that the effects of the RHPz can be mitigated to improve transient output performance by reducing the input capacitance of the Buck converter. However, excessively decreasing the input capacitance may cause the system's resonant peak to cross the 0 dB line in the frequency domain, leading to a -180° phase shift and potential instability. Reducing bandwidth is necessary to keep the system stable, but this approach compromises the Buck converter's transient performance. To address the resonant peak issue associated with small input capacitance, this research proposes an active damping control technique, which includes input capacitor voltage feedback and appropriate damping design. This strategy significantly enhances transient performance and increases system bandwidth. The effectiveness of the proposed control strategy is validated through simulations and experiments.