Design Of Off-grid Micro-inverter Based On Lithium Battery Energy Storage

Off-grid micro-photovoltaic inverter is the core component of distributed photovoltaic power generation system,and it is also an issue extensively discussed and studied.As an important form of utilization of solar energy,A complete off-grid inverter system usually comprises energy storage components,so it can store excess electricity that has been transferred from solar power when sunshine is enough,and it can provide load with power when sunshine is inadequate.Inverter technology is the core technology of this system,and this paper presents a kind of design method of digitized control off-grid micro-inverter system with lithium battery energy storage based on FPGA,and then invents a 300 W micro-inverter,which is centered on the development of micro inverter experimental prototype.This paper at first tells the working principle of various components of micro-inverter system,and decides to choose two-stage push-pull fullbridge inverter topology as the main topology of the inverter,and proposes a kind of unipolar doubled-frequency sinusoidal pulse width modulation(SPWM)digital inverter control scheme;and then conducts a deeper research into the basic characteristics of two-way circuit and lithium batteries and the working principle of battery voltage monitoring and management system and so on.Then this paper has carries the detailed hardware and software design on the basis of introducing the working principle of the system.Hardware circuit design includes parameter calculation and selection of main device of main power circuit,driving circuit and the design of AD sampling and conditioning circuit.This paper carries detailed design on function realization of each module in FPGA by using Verilog HDL hardware describe language,and expounds on the design flow of doubled-frequency SPWM with deadtime control and verifies the feasibility of the scheme through the corresponding simulation.This paper designs lithium battery management system based on LTC6804 and designs the peripheral hardware circuit of LTC6804,using FPGA as main controlled to drive the LTC6804,and reads the corresponding statistics and displays on the upper computer through serial port,and completes the Function of lithium battery management system.On the basis of the deep study and research of voltage and current double-loop control strategies of fullbridge inverter,this paper builds the corresponding PSIM model for the main and feedback circuits of the inverter,and verifies the feasibility of the scheme through the corresponding simulation.The paper finally tests the prototype and provides the corresponding wave results of the experiment.