Design And Implementation Of An Off-grid Inverter For Low Voltage Energy Storage System

Energy is the foundation of the development of human life.In particular,a wonderful life is inseparable from electric energy.It is widely acknowledged that electric energy has become an indispensable part of our life with its advantages.The power grid is the most common source of electrical energy,but with current technical conditions,there are still links that are not covered by the grid.In some outdoor situations where electricity is needed,energy storage systems can be used to provide energy,which can be converted into alternating current through inverters.Due to the low voltage of a single battery cell,common battery energy storage systems are mostly composed of several batteries in series.For lithium-ion batteries,the voltage discharge range is wider,which is more obvious after series connection and grouping.Meanwhile,there is also difference between the batteries.The difference is not conducive to the design of the battery management system.The number of cells in the battery pack should not be too much,usually a few are often used to form a low-voltage energy storage system.In order to make full use of the energy of the energy storage system and ensure the effective release of the stored energy,this paper designs a set of portable off-grid inverters for low voltage energy storage equipment.The main work of the research are as follows.(1)The paper studies the common topology of inverters,analyzes the working principles,advantages and disadvantages of different topology,and chooses a design scheme that combines a push-pull boost circuit with a full-bridge inverter circuit,converting the low-voltage DC into the high-voltage DC,and then obtaining AC power that meets the electrical equipment.Aiming at the low voltage of the DC bus at low voltage input,a DC voltage regulation link based on Boost circuit is designed.(2)Through the comparative analysis of the advantages and disadvantages of unipolar and bipolar modulation methods in control,the unipolar modulation method is selected in the downstream inverter control strategy.The AC small signal model is established for the Boost circuit,and the controller design is completed by using the frequency domain method.The functions and control strategies of each link are verified by simulation.(3)Combining with the system design indicators,the thesis completes the design of the main circuit module,power supply module,control module,drive module,and sampling module.The circuit schematic diagrams and printed circuit board diagrams have been drawn.It also compiles control algorithms and builds the inverter system experimental prototype.The system has realized the functions of boost,DC voltage regulation,inverter,and so on.And the whole machine has been tested.The result shows that the output voltage of the system is stable and meets the design index requirements,the inverter can work normally at the upper and lower limits of the output voltage of the energy storage system,and the overall output power can reach1200 W.