A Robust Power Management Strategy with Multi-mode Control Features for an Integrated PV and Energy Storage System to take the Advantage of ToU Electricity Pricing
In this paper, a power management strategy (PMS) for an integrated residential solar photovoltaic (PV) and energy storage unit (ESU) is proposed for both grid-connected and islanded operations to take advantage of time-of-use pricing. This is an effective solution to integrate storage and renewable energy sources, such as solar PV, with the conventional utility grid to improve the reliability and efficiency of the power system and to reduce the total electricity cost for the consumer. An automatic switching control strategy is proposed to realize a smooth switching among 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. The PMS ensures seamless switching of the ESU converter between the charging and the discharging mode and seamless switching between the inverting and the rectifying mode of the grid converter. It also ensures that the local loads are supplied when the ac grid fails. An experimental setup has been implemented 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 under the various scenarios of PV irradiation, load demand changing and the state of charge of the energy storage unit. The results show that the proposed PMS is effective and robust against various scenarios.