Abstract : Electric drive systems are generally classified into two main categories: DC drive systems and AC drive systems. AC drives are more commonly used. However, in equipment and applications requiring speed regulation, DC motor speed control systems and slip-ring motor speed control systems are more commonly used. Both DC motor speed control systems and slip-ring speed control devices have significant drawbacks in practical applications. Since the advent of switching devices such as thyristors and inverter technology, AC motor speed control has been revitalized and has developed rapidly. With the continuous development of electronic technology, AC motor speed control will increasingly show broad prospects, gradually replacing DC motor speed control and other speed control methods. This is an inevitable trend in the development of modern speed control systems. Keywords : AC frequency conversion; frequency converter; speed regulation. According to the characteristics and requirements of power production system processes, some production equipment requires speed regulation, such as coal feeding, pulverized coal feeding, and water supply and drainage systems. In the past, speed regulation of these systems was accomplished using DC motors and electromagnetic slip clutches (i.e., slip-ring motors), or by directly starting and stopping high-voltage motors. Years of production practice have proven that these speed control systems all have many drawbacks, causing certain impacts on production. While DC motor speed control systems offer sensitive control and fast response, their drawbacks include large footprint, low efficiency, and inconvenient maintenance. Slip-ring speed control devices, though simple and easy to use, suffer from low efficiency and frequent malfunctions. AC motors, on the other hand, are simple in structure, reliable in operation, low in cost, and require minimal maintenance. 1. AC Variable Frequency Speed ​​Control System Variable frequency drives (VFDs) can be broadly classified into AC-DC-AC VFDs and AC-AC VFDs. AC-DC-AC VFDs are further divided into voltage-type and current-type VFDs, and by control method, into pulse width modulation (PWM) and pulse amplitude modulation (PAM) types. The working principle of an AC-DC-AC VFD is shown in Figure 1. Its internal structure mainly consists of a main circuit and a control circuit. [b][align=center]For more details, please click: Application of AC Variable Frequency Speed ​​Control Technology in Power Plants[/align][/b]