An autonomous solar PV system using boost TPC for energy harvesting with mode-based power flow management control

Energy harvesting from environment provides a compelling alternative to battery-powered standalone systems. The rising use of green energy resources in energy sector has a substantial impact on the low voltage DC (LVDC) systems. Multiport converters make it easier to convert renewable energy for use in everyday situations. To ensure uninterruptible power supply, a non-isolated Three-Port Converter (TPC) acts as a gateway for renewable sources, energy storage, and loads. The paper describes a modified power flow management control for a standalone solar PV system using boost TPC with time sharing control and an added mode-based controller for voltage regulation. To operate the TPC effectively in Dual Output (DO), Dual Input (DI) and Single Input and Single Output (SISO) modes, localized controllers are used. The converter small signal model is developed for all operating modes and based on this, sampled data control theory is applied to design the digital controller for load regulation. When the TPC switches from one operating mode to another, the voltage regulation control sets the controller parameters for the appropriate mode. Also, to extend battery lifespan, the control algorithm includes a battery overcharge prevention mechanism. The proposed algorithm is realized in a System on a Programmable Chip (SoPC) using the Field Programmable Gate Array (FPGA) Cyclone-III and Nios-II as processor. The system is tested in real time with solar PV as the source of energy and a lead-acid battery as the storage.