AC is a form of electrical energy in which the direction of current and the polarity of voltage change periodically. It is widely used in households, industries, and power grids. Unlike direct current (DC), AC can easily increase or decrease the voltage through a transformer, which is convenient for long-distance transmission. In the battery industry, although the battery itself stores and outputs DC power, in many application scenarios (such as electric vehicle charging and energy storage system grid connection), DC power needs to be converted to AC power through an inverter to achieve compatibility with the power grid or AC equipment. Therefore, understanding and applying AC power is a key link in battery system design and energy management.