In thermal power plants, fans and pumps are the most significant power-consuming equipment. They operate continuously for extended periods and often under varying loads, presenting substantial energy-saving potential. The economical operation of auxiliary equipment directly impacts the plant's power consumption rate. Taizhou Power Plant's Unit #7 has a rated capacity of 330MW. Unit #7 is equipped with two centrifugal primary air fans, driven by 6kV, 1600 kW constant-speed motors. The primary air volume is adjusted by regulating the opening of the inlet damper to adapt to boiler load changes. Due to the initially large air volume and pressure margins, before the modification, the primary air fan current at full load was approximately 120A, the damper opening was approximately 60%, and the air pressure was approximately 8.9 kPa, resulting in significant throttling losses. Against this backdrop, a frequency converter control modification was implemented for the primary air fans of Unit #7 to reduce power consumption. I. Feasibility Analysis The primary air fan is one of the main pieces of equipment in the direct-fired pulverizing system of a coal-fired boiler in a thermal power plant. The air volume is adjusted by controlling the opening of the inlet damper of the primary air fan according to the boiler's operating conditions. From a technical perspective, motor speed control can employ methods such as hydraulic couplings, electromagnetic slip clutches, rotor resistance speed regulation for wound-rotor motors, pole-changing speed regulation, and frequency converter control. Based on the development of power electronic devices, frequency converters, and AC motor control technologies, many research institutions and large companies both domestically and internationally have invested significant resources in researching medium- and high-voltage frequency converters. High-voltage frequency converter technology has matured and has become the preferred solution for motor speed control. [b][align=center]For more details, please click: Case Study of Medium-Voltage Frequency Converter Retrofit for Primary Air Fans at Taizhou Power Plant[/align][/b]