Robust dual-loop sliding mode control for MPPT and grid-interfacing inverter regulation in a hybrid PV-battery system

Photovoltaic systems interfaced through a boost converter and a grid-tied inverter form a nonlinear, time-varying cascade that conventional PID control struggles to regulate across changing irradiance and load conditions. This paper presents a dual-loop sliding mode control (SMC) architecture for a hybrid PV-battery system: an SMC-MPPT loop regulating the boost converter’s DC bus voltage, and an SMC current loop regulating a grid-tied inverter under Unipolar PWM. Both loops are derived from a unified methodology - sliding surface design, exponential reaching law, boundary-layer control law, and Lyapunov stability proof - applied within a single state-space model spanning the PV array, boost converter, battery, and inverter. Simulation results show the converter settling within 2.35 s of an irradiance transient with sub-3% ripple, and the inverter maintaining unity power factor across a variable 24-step load profile. Over the wide range of irradiance tested, the SMC-MPPT scheme can supply an average of 98% higher power than a stand-alone configuration. The output of the two loops works independently, and it is not affected by each other via the common DC bus, according to the separation of time-scales principle embodied in our system model. The primary future validation direction is established as a controlled comparison against a PID/P&O baseline under identical disturbance profiles.