FREQUENCY DOMAIN CLOSED-LOOP ANALYSIS AND SLIDING MODE CONTROL OF A NONMINIMUM PHASE BUCK-BOOST CONVERTER

摘要

In this paper, a robust closed-loop cascaded controller is designed and analysed for an inverting buck-boost converter. The fast inner current loop uses sliding mode control (SMC). The slow outer voltage loop uses the proportional-integral (PI) control. Analysis of stability and robustness, proof of nonminimum phase structure, and proper selection of PI gains are based on the closed-loop transfer function. The controller design is facilitated by the system frequency responses. The output voltage transients caused by step changes of the input voltage and load resistance are predictable. The operating range of the reference voltage is discussed. The simulation results show that the reference output voltage is well tracked under modelling uncertainties, disturbances or step changes of parameters, confirming the validity of the proposed method.