Wind turbines are machines that convert wind energy into electrical energy. From the perspective of energy conversion, the wind turbine consists of two major components: one is the wind turbine, whose function is to convert wind energy into mechanical energy; the other is the generator, whose function is to convert mechanical energy into electrical energy.
   
    Small wind power generation system structure. It generally consists of wind turbine, generator, rudder and electrical control part, etc. Conventional small wind turbines are mostly composed of induction generators or permanent magnet synchronous generators plus AC/DC converters, batteries, and inverters. Under the blowing of the wind, the wind wheel rotates so that the aerodynamic energy is converted into mechanical energy (rotational speed + torque). The hub of the wind turbine is fixed on the generator shaft, and the rotation of the wind turbine drives the rotation of the generator shaft, which drives the permanent magnet three-phase generator to generate three-phase alternating current. The wind speed changes constantly, fluctuating, and the current and voltage from the generator also change. The issued electricity is rectified by the controller, and the alternating current is changed into direct current with a certain voltage, and is charged to the battery. The DC power output from the battery pack is turned into 220V AC power through the inverter, which is supplied to the user's household appliances.
   
    Wind turbines are categorized into grid-connected and off-grid wind turbines depending on the application. Off-grid wind turbines, also known as stand-alone wind turbines, are wind turbines that are used in areas without power grids, and are generally smaller in power. Stand-alone wind turbines are generally required to form a stand-alone wind turbine power generation system together with batteries and other control devices. This kind of independent operation system can be a few kW or even dozens of kW to solve the power supply system of a village, or it can be a few dozens to hundreds of W of small wind turbines to solve the power supply of a household.