Photovoltaic battery charger with sliding mode control and charging current derivative limitation

Abstract

In stand-alone photovoltaic (PV) systems, battery chargers are important to guarantee the energy supply when sunlight is not available. Such chargers need to track the maximum power point (MPPT) and limit the derivative of the batteries’ charging current to extend their lifetime. This paper proposes a battery charging system composed of a Buck converter, a cascade control of the battery current and the PV panel voltage, and the Perturb and Observe (P&O) MPPT technique. P&O generates the reference of the panel voltage for the external loop of the cascade control implemented with a P regulator, whose control action is the reference of the batteries’ charging current. Such current reference passes through a derivative limiter before reaching the internal current control loop, which is implemented by a sliding-mode controller (SMC). This paper includes transversality and reachability analyses of the SMC, as well as the procedure to design the P regulator. The proposed system is validated by simulations in PSIM software to show its capacity to perform MPPT and limit the battery’s charging current derivative at the same time

Keywords

• Battery charger
• photovoltaic panel
• Buck converter
• sliding-mode control
• current derivative limitation