PV-Battery Series Integration for Residential Solar-plus-Storage Systems

Solar-plus-storage systems provide efficient energy yield and management, resilience, and more revenue to residential houses and buildings. In solar-plus-storage systems, power electronics converters are integral components to generate the maximum output power from a solar photovoltaic (PV) array, store the generated energy into a battery, and finally deliver and manage the power to an electric load or the electric grid. Many existing solar-plus-storage systems still use and combine legacy power electronics convert topologies initially designed for a solar PV generation system or a battery energy storage system (BESS) separately. These power converters are connected in parallel to an AC or DC point of common coupling: AC-parallel and DC-parallel integration methods. Another integration method of a solar-plus-storage system is connecting a high-voltage battery to the high-voltage DC bus in parallel in a solar PV generation system having two-stages power converter architecture: In-line integration method. These methods result in increased costs and size, lower energy yields due to the increased number of power electronics converters, and the requirement of high-voltage PV strings and batteries.
This research studies new PV-battery integration methods and develops PV-battery series optimizers—power electronics converters optimally designed for different residential solar-plus-storage systems. The two PV-battery integration methods are proposed: AC-series integration and DC-series integration. The proposed integration methods are based on the series connection of PV and battery modules. The AC-series integration method assists the residential panel-level series-connected solar PV inverters in reducing the intermittent PV output fluctuations with a low-voltage-profile battery energy storage inverter. The DC-series integration enables PV voltage support, reducing the number of power converter stages, reducing the rated power of power converters, improving the system round-trip efficiency, and seamless source integration. Three PV-battery series optimizers are developed for different solar-plus-storage applications. The proposed power converter topologies and controls are discussed in this dissertation. Off-line simulation, real-time controller hardware-in-the-loop simulation, and lab-scale experiment results are included and analyzed to demonstrate the operating and design principle and the control performance of the proposed system.