Abstract : The motors in rolling mills have high power consumption and severe interference, making speed regulation accuracy difficult to control. This paper proposes an advanced and reliable digital control speed regulation technology that solves these problems. Frequency conversion employs filtering measures to mitigate harmonics from the power grid. This technology has significant reference value for the design and application of frequency conversion speed regulation. Keywords : Control structure, filtering, compensation 1 Introduction The speed regulation scheme for the eight main drive AC motors of the 1500mm hot strip mill at Laiwu Steel Company adopts an AC-AC frequency conversion speed regulation system. The main drive motor is an AC synchronous motor, using products from Dongfang Electric Machinery Factory. The controller is a vector control AC-AC frequency converter digital controller composed of a Siemens SIMADYN D all-digital 64-bit processor. The power unit adopts a Y-connected AC biased main circuit structure composed of three-phase non-circulating current reversible thyristor converters. The rated current of the main motor and power unit is designed for long-term operation at 115% of the motor's rated current, and is also designed to operate at 125% of the motor's rated current for 2 hours. The F1 to F6 main motors and AC-AC frequency converters are designed for 60 seconds of overload operation at 200% of the motor's rated current. The R1 main motor and AC-AC frequency converter are designed for 60 seconds of overload operation at 250% of the motor's rated current and 15 seconds of overload operation at 275% of the motor's rated current. The power components of the AC-AC frequency converter are products from ABB Power Electronics Research Institute to ensure quality. The main drive AC-AC synchronous motor stator and both side bearings are equipped with temperature sensors. Grounded carbon brushes are installed on the main drive motor to eliminate shaft current. The main motor is cooled using a backpack-style air-water cooling system. The cooling backpack is equipped with sensors for air temperature, air pressure, water temperature, and water flow to ensure reliable motor cooling. Speed ​​measurement of the AC-AC synchronous motor's AC-AC variable frequency speed control device is performed using a German HUBNER large-shaft encoder. Digital control utilizes a Siemens SIMADYN D original digital control cabinet. The Siemens SIMADYN D uses a UNIX operating system and installs Siemens' STRUC G graphical programming software. This system employs a graphical, freely programmable, modular, freely configurable, and multi-processor parallel real-time processing general-purpose digital control system. It is suitable for high-power closed-loop electrical drive control with high technical performance requirements, and can meet various complex and precise control requirements. It is widely used in fields such as high-precision rolling mill main drives (high-power AC/DC drives), high-power coiler drives, flying shear drives, multi-motor control, tension control, hydropower generation systems, ultra-high-power starting systems, high-voltage DC transmission systems, and dynamic reactive power compensation systems for power grids. The system hardware mainly consists of a main chassis, auxiliary chassis, and interface terminal boards. The main chassis mainly consists of general-purpose microprocessor units, dedicated microprocessor units, various auxiliary units, interface units, communication units, and power supplies. The auxiliary chassis mainly consists of thyristor interface units. The interface terminal boards are mainly used for directly connecting analog and digital I/O, as well as connecting encoder signals. [b][align=center]For more details, please click: Application of Digital Control AC-AC Variable Frequency Speed ​​Regulation Technology in Hot Strip Mills[/align][/b]