Control And Protection Of Hybrid System With PV And Battery Storage

Hybrid system control with PV and energy storage is the key issue in its actual operation. In view of the variation of renewable energy, load and topology in the micro-grid, how to achieve the effective coordination and control of solar power and battery, to ensure the power quality under a variety of states, is the key problem for its reliable operation.Connected to the distribution network, the PV and battery hybrid system will change the level of its fault current, which will affect the selectivity, sensitivity and reliability of traditional current based distribution network protection. The access of PV and battery in micro-grid will completely change the distribution network fault characteristics, resulting in different electrical changes after fault compared to the situation in traditional distribution network, that the traditional distribution network protection principle and fault detection method may not work accurately and effectively. So it need to re-analysis of protection principle and reset protection based on the specific control logic and fault characteristics for micro-grid.The change of user side reactive load in distribution network will have a great impact on the voltage at the end of power supply. With the large-scale application of PV power generation system in distribution network, to ensure that PV system running efficiently, and improve the quality of power supply is particularly important. In this paper, based on the analysis of mathematical model and external characteristics of photovoltaic and battery, the hybrid system simulation model with PV and battery storage is built under both different modes of grid-connected and islanding. By analysis of the traditional inverter control principles, this paper presents a novel inverter control strategy aim at reactive load fluctuations. It makes full use of the original topology of the inverter circuit to achieve the dual control objectives of both grid connection and reactive power compensation. It adopts double-loop control, decouples the current from grid side and inverter to active and reactive component respectively. On the one hand ensures the maximum active output by maximum power tracking technology; on the other hand adjusts the reactive power supply of the grid to ensure the voltage stability with the change of reactive load. It achieves dual control objective of maximum power output and the supply voltage stability. Theoretical studies and simulation tests verifies the effectiveness and superiority of the novel grid-connection control. Given the special nature of the inverter connected source and its control logic, this paper presents the fault analysis of PV and battery hybrid system under grid-connected mode, and introduce a relevant protection scheme based on current.