Abstract: This article focuses on the working principle of multi-level high-voltage frequency converters and their application at Dagang Power Plant, providing detailed statistics and comparisons of their energy-saving effects. The results show that using high-voltage frequency converters for fan speed regulation and energy-saving retrofitting has high economic benefits and a significant effect on reducing plant power consumption. Keywords: High-voltage frequency converter; Frequency converter; Energy saving I. Project Overview Dagang Power Plant has four 320MW units with a total installed capacity of 1280MW, all imported from Italy. After the first phase of boiler renovation, the boiler measuring equipment is domestically produced. To ensure the safe and stable operation of the units, the standby capacity of each auxiliary machine is relatively large. During summer full-load operation, the fan damper opening is around 75%–80%, resulting in significant capacity loss, low fan efficiency, and reduced service life of motors and machinery, leading to a substantial increase in maintenance workload and costs. In terms of power generation in 2004, Unit #4 generated 1.998 billion kilowatt-hours, with an average annual load of 255.8 MW, representing a load factor of 77.87%. The plant's power consumption rate was approximately 9%. To reduce this rate, the plant actively sought new equipment and technologies to upgrade existing auxiliary equipment starting last year, aiming to achieve energy conservation, reduce consumption, and enhance its market competitiveness. Since the blowers are high-voltage motors with large single-unit capacity, long operating times, and high power consumption, the plant had significant potential for energy saving. Therefore, it decided to retrofit the two blowers of Unit #4 with variable frequency speed control for energy saving. The variable frequency retrofit project for the blowers of Unit #4 was initiated in 2004, and a technical agreement was signed in October 2004. The equipment arrived at the end of December 2004 and was installed and commissioned during a minor overhaul in February 2005. After the overhaul, the frequency converter was officially put into operation and has been running for over six months. All operating parameters are normal. It interfaces and communicates with the existing DCS system, facilitating remote control and local operation. Operation is reliable, and the energy-saving effect is very significant. [b][align=center]For detailed information, please click to download the Energy-Saving Effect Analysis of the Frequency Converter Retrofit for the Boiler Blower at Dagang Power Plant[/align][/b]