Power management and bus voltage control of a battery backup-based stand-alone PV system

The modeling and control of a stand-alone solar photovoltaic with battery backup-based hybrid system is implemented in this paper. Normally, a hybrid PV system needs a complex control scheme to handle different modes of operations. Mostly, a supervisory control is necessary to supervise the change in controller arrangement depending on the applied mode. The proposed system consists of a dc-dc boost converter, a single-phase inverter and a bidirectional dc-dc converter. The PV array is interfaced through a dc-dc boost converter and is controlled with the help of an MPPT controller to extract the maximum power. The battery backup unit is integrated with the PV system through a common dc bus for the power management within the system as well as to maintain a constant dc bus voltage. The power exchange between the battery and dc bus can be controlled by a bidirectional buck-boost converter. The system can be operated with or without battery units, having no alteration of the control configuration, as a result use of complex supervisory controller can be avoided. For simple circuit architecture to be realizable, a control scheme based on sliding mode control is designed for the full-bridge inverter. Its purpose is to maintain a sinusoidal output voltage with small steady-state error, lower total harmonic distortion (THD) and excellent dynamic response under step change in load. Finally, the simulation results from a two-stage 2 kW, 110 V, single-phase stand-alone PV system are provided to confirm the theoretical analysis, effectiveness and feasibility of the proposed control scheme.