Control And Energy Management Research Of The Single Phase Grid-tried Or Off-grid Photovoltaic Energy Storage System

With the worldwide energy crisis and environmental deterioration, solar photovoltaic technology for its compliance with the requirements of sustainable development strategy is utilized by various countries. Due to the diversity and randomness of its own modules distributed PV systems, control and energy management of the energy of the whole system has become a current research focus. Based on the analysis of the generation of photovoltaic technology status and associated control, control and energy management strategy of a distributed photovoltaic energy storage system that was composed of solar photovoltaic batteries, lead acid batteries, the local load and grid were studied.First of all, the whole structure of grid-connected and off-grid solar energy storage system was put forward: DC bus structure, the structure has strong extensibility and high stability. Secondly, on which the photovoltaic cell and lead-acid battery energy storage unit operating characteristics were analyzed in detail, while the corresponding power conversion unit PV Interface converters, bidirectional DC/DC converter and a single-phase inverter circuit were studied. On the other hand, the photovoltaic maximum power point tracking(MPPT) algorithm and the storage battery charging and discharging control strategies were designed, and the design MPPT algorithm was simulated.Then, in view of the characteristic that the system can run in grid or off-grid, the paper focused on designing control strategy of inverter in the system grid-connected state and off-grid state. And current inner loop and voltage outer loop PI controllers were designed. On account of the problem that the capacity of inverter with driving nonlinear load on the system off-grid state is limited, a improved double loop control method adding output current feed forward control of was proposed, simulation results demonstrate that the improved control method can greatly provide the system ability with driving nonlinear load on off-grid state.Since the system consists of the photovoltaic power generation unit, battery energy storage unit, power grid and a load module, reasonable energy management strategy of the whole system is generated to ensure the system of energy supply and demand balance. Based on the dc bus system structure, the paper reference and improve dc bus voltage level signal control method. The whole operation process system of system can be divided into four working mode according to the improved control strategy. Both the running state of every mode and the energy transfer between the mode switch were analyzed in detail. Finally, the simulation model of system was built in the simulation software, and the improve the energy control strategy has carried on the simulation. The simulation results show the feasibility of control strategy.