Second-order sliding mode controller design of buck converter with constant power load

Abstract

Multi-converter systems used in DC microgrid feed supply constant power loads (CPL) as well as classical electrical loads. CPL has a non-linear load nature because of the negative impedance effect. This impact causes instability in converter systems within the micro-grid. This paper proposes a super twisting-based second-order sliding mode control (SOSMC) for regulating the output voltage of a DC/DC buck converter feeding CPL. The goal of this method is to suppress the chattering effect and maintaining the robustness under load variations and parametric uncertainties. With the experimental studies constructed in the laboratory and simulations executed in Matlab environment, the proposed SOSMC was compared with classical first-order SMC for the response of the buck converter feeding CPL under various conditions. The simulation and experimental results show the proposed controller has higher tracking precision and stronger robustness during any disturbance in input voltage or CPL power, as well as reducing the chattering effect.