On Effect of Right-Half-Plane Zero Present in Buck Converters with Input Current Source in Wireless Power Receiver Systems

TL;DR

This paper investigates how right-half-plane zeros, caused by the current source nature in wireless power receiver buck converters, affect control performance and stability, supported by theoretical analysis and experimental validation.

Contribution

It identifies and mathematically proves the origin of RHP zeros in buck converters with current sources, highlighting their impact on control design and stability in wireless power systems.

Findings

RHP zeros are introduced by the current source nature and finite capacitance.

RHP zeros cause non-monotonic dynamic responses.

They complicate feedback control design and can lead to instability.

Abstract

In wireless power receiver systems, the buck converter is widely used to step down the higher rectified voltage derived from the wireless receiver coil, to a lower output voltage for the immediate battery charging process. In this work, the presence and effect of the right-half-plane (RHP) zeros found in the small-signal inductor-current-to-duty-ratio and output-voltage-to-duty ratio transfer functions of the buck converter in the wireless power receiver system on the control performance, are investigated. It is found and mathematically proved that the RHP zeros are introduced by the current source nature of the system attributed to the series-series compensation and finite DC-link capacitance. The RHP zero not only results in non-monotonic open-loop dynamic response but also complicates the design of feedback control and causes potential closed-loop instability. Theoretical and experimental results are provided to validate the presence of the RHP zeros and their effect on open-loop and closed-loop dynamic responses.