Flexible System Architecture of Stand-Alone PV Power Generation With Energy Storage Device

A standalone photovoltaic (PV) system with energy storage requires a complex control architecture to take into account the various operating modes. In many cases, a supervisory controller is necessary to manage the change of the control architecture according to the applied mode. This paper presents a flexible architecture of a PV power conditioning system with energy storage. The proposed conditioning unit contains a boost converter (BC), a single-phase inverter, and a bidirectional dc/dc converter connected to the PV side of the BC. The BC regulates the dc-link bus-voltage. The bidirectional dc/dc converter endures battery bank charge/discharge control and PV maximum power point tracking (MPPT). Such architecture guarantees nonchange in controller configuration when the storage disconnects. Therefore, the previously needed supervisory controller is eliminated. A system control strategy based on sliding-mode control (SMC) ensures a reliable output voltage regulation such as fast dynamic response, small steady-state error, and low total harmonic distortion (THD) under step changes and nonlinear loads. The controller structure, the dynamic behavior, and the design procedures are introduced. Finally, the validity of the proposed module with control strategy is verified through hardware experiments on a 500-W prototype test bed with a single TMS320F28335 DSP module.