Stability and Controller Design of a Two-Stage IPT System

This article focuses on stability analysis and control in a two-stage inductive power transfer (IPT) system. It aims to derive an accurate output impedance model for the unregulated IPT stage, investigating its impact on the downstream buck converter. Practical considerations for bus capacitance and controller type are discussed to balance stability, filter size, and bandwidth, emphasizing the practical importance of impedance analysis for stable multistage IPT setups. A practical 200-kHz system is constructed to verify the stability analysis. The use of an analytical model, grounded in clear physical interpretations, assists in guiding the linear control of the buck converter at a high crossover frequency 28 kHz. Alternatively, it aids in selecting a conservative control approach to reduce the bus capacitance.