A robust power management strategy entrenched with multi-mode control features for an integrated residential PV and energy storage system to take the advantage of time-of-use electricity pricing
In this paper, a power management strategy (PMS) for an integrated residential solar photovoltaic (PV) and energy storage unit (ESU) in both grid-connected and islanded operations to take advantage of time-of-use pricing is proposed. This is an effective solution to integrate renewable energy sources with conventional utility grid to improve reliability and efficiency and to reduce total electricity cost, especially for solar PV generation. This paper proposes an autonomously switched control strategy to realize smooth switching between the various operation modes of the proposed energy management strategy. The integrated PV-storage system is composed of a 5 kW PV arrays, a 3.5kWh ESU formed by 12V single lead acid batteries, and three power converters. By using the proposed power management strategy, the integrated PV/storage system can accomplish power control by charging and discharging the ESU unit. It also guarantees that the local loads are powered when the ac grid fails. The PMS ensures seamless switching of the ESU converter between the charging and the discharging mode and seamless switching between the inverting and rectifying mode of the grid converter. An experimental setup has been built in the laboratory using the real time FPGA GPIC (General Purpose Inverter Control) card from National Instrument to verify the practical feasibility of the proposed PMS and the results obtained for various scenarios of PV irradiation, load demand and the grid output demonstrate the effectiveness of the proposed control strategy.