With the increasing attention paid to new energy and smart grid in our country, battery energy storage system has broad application prospects in power electronics technology. Battery energy storage system has flexible capacity configuration and peak shaving and frequency regulation abilities, but its electrochemical properties currently restrict their practicality and development towards larger capacity and easier maintenance. Therefore, how to use power electronic devices as a link to communicate between the completely different system structures of power electronics and electrochemistry, on the one hand, to provide functions such as new energy coordination, peak shaving and valley filling, and reactive power support for the power grid, and on the other, to ensure the normal service life of batteries, different series-parallel connection methods, and efficient adaptation to different battery types, are all technical issues worth exploring.
According to the positive electrode materials, lithium batteries can be divided into lithium manganate batteries, lithium cobaltate batteries, ternary material batteries, and lithium iron phosphate batteries. The cobalt in lithium cobaltate batteries is a very valuable resource and is very expensive. Also, due to the high safety risks under high temperature and charging conditions, lithium cobaltate batteries are not suitable for large-capacity battery energy storage. Lithium manganate batteries, which are cheap, environmentally friendly, and good in safety, have abundant positive electrode materials resources and have been successfully applied in electric buses and electric vehicles in recent years, achieving significant breakthroughs. Ternary material lithium batteries, which are relatively low in cost and safe, are actually substitutes for lithium cobaltate batteries. Lithium iron phosphate batteries have obvious advantages in terms of cycle life, manufacturing cost, and safety, and their energy density is only three-quarters of that of lithium cobaltate batteries, making them suitable for the energy storage system.
Batteries complete the mutual conversion between electrical energy and chemical energy through the chemical reaction between the electrodes and electrolyte and the connection of the external circuit. They are devices that use the principles of electrochemistry for energy conversion and storage. Battery energy storage systems have flexible configuration, are not restricted by resources and geographic environment, and can be connected to the power grid system through power conversion equipment (PCS) to quickly adjust reactive and active outputs, making them more suitable for the new generation of new energy power electronics and the needs of new energy development.
From the perspective of power system applications, a battery energy storage system is actually a DC voltage source consisting of thousands of battery groups connected in series and parallel to form a large-capacity battery stack, which also constitutes a charged capacitor and an inner risk DC voltage source. However, this energy cannot be directly used for AC power grids, so appropriate energy conversion equipment is needed to convert DC into AC, which generally requires the application of modern power electronics devices and technology.
Power electronics technology, which began with the birth of the first thyristor in 1957, has rapidly developed semiconductor switching devices and promoted the application of power electronic devices in various industries, from household appliances such as TVs, washing machines, and air conditioners to internal frequency converters in large factories and steel rolling mills and to high-voltage DC and reactive power compensation in power systems. These power electronic devices can be seen in various industries.