Energy is the material foundation of economic development and a significant constraint on economic, social, scientific, and sustainable development. As the world's second-largest energy consumer, China has always attached great importance to energy and energy conservation. As early as the early 1980s, it proposed the policy of "giving equal importance to energy development and conservation, with conservation as the priority," incorporating energy conservation into the national economic and social development plan. Currently, with my country's rapid economic growth, the contradiction of insufficient energy is becoming increasingly apparent. Its characteristics are: 1. Relatively insufficient per capita energy. The per capita energy resources in most parts of my country are less than half the world average. 2. Low energy efficiency. my country's energy consumption per million US dollars of GDP is 2.4 times higher than the world's advanced level, and its energy efficiency is 10 percentage points lower than the international advanced level. 3. Prominent energy constraints. In recent years, bottlenecks in coal, electricity, oil, and transportation have reappeared. 4. Severe environmental pollution. my country is one of the few countries that relies heavily on coal as its primary energy source and is also the world's largest coal consumer, resulting in enormous environmental pressure from energy use. To accelerate the construction of a conservation-oriented society, alleviate the current shortage of coal, electricity, oil, and transportation, and address the resource constraints and environmental pressures faced in building a moderately prosperous society in all respects, and ensure the sustained, rapid, coordinated, and healthy development of the national economy, every power generation company and power plant should fully recognize its social responsibility and take energy conservation, improved energy efficiency, and reduced environmental pollution as the intrinsic driving force for the company's sustainable and healthy development. From a macro perspective, energy conservation aims to reduce energy consumption per unit of output; from an industry perspective, it means reducing the energy consumption per unit of product. At the end of 2001, to further implement the requirements of the leadership of Datang International Power Generation Company to "focus on reducing plant power consumption rate with the goal of ensuring safe production, improving equipment health, and increasing economic efficiency," the company decided to make high-voltage auxiliary equipment frequency conversion a key energy-saving measure for 2002. Relevant professionals of the company have been studying relevant information on high-voltage frequency converters since 1999 and paying attention to the status of high-voltage frequency converters already in operation. To further understand the use and maintenance of frequency converters and the production status of domestic manufacturers, the company's frequency converter research team conducted research on some power plants and manufacturers in early 2002. They conducted in-depth and detailed discussions on issues related to operation, technology, and benefits, and performed detailed economic benefit calculations for the project. After careful comparison and calculation, a tender was issued. To date, the company has put 42 high-voltage frequency converters into operation, generating significant economic benefits. The following is a detailed comparative analysis of the economic benefits of various high-voltage frequency converter retrofits for different capacity units: I. Economic Benefit Comparison: High-voltage frequency converters are distributed across the company's 100-600MW units, mainly including primary air fans, forced draft fans, induced draft fans, and condensate pumps. The detailed comparison of relevant economic benefits is as follows: 1. Zhangjiakou Power Plant #8 Boiler (300MW Unit) Primary Air Fan: The pulverizing system配套的张家口动力植物 #8沸子的正压直吹型系统，设备6ZGM95G型中速煤磨磨磨). Both the forced draft fan and the induced draft fan are adjustable-blade fans manufactured by Shanghai Blower Factory. Since the primary air fans of units #7 and #8 are of the same model, but unit #7 was not equipped with a frequency converter during the test, comparative tests with unit #7 showed that at 150MW, 200MW, 250MW, and 300MW, the power of the primary air fan in unit #8 was reduced by 1127 kW, 946 kW, 689 kW, and 809 kW respectively compared to unit #7. Based on the unit operation in 2001, with an average unit load of 200 MW, an annual operating hour of 7200 hours, and a grid electricity price of 0.3 yuan/kWh, the primary air fan in unit #8 saved 6.66 million kWh of electricity annually, resulting in a saving benefit of 2 million yuan. The energy-saving effect was particularly significant under low-load conditions. The price of the two high-voltage frequency converters was 5.6 million yuan, and the entire cost could be recovered in less than three years, making the investment return ratio quite good. 2. The induced draft fans for Boiler #2 (100MW unit) at Xiahuayuan Power Plant are model Y4-73-11, with a motor power of 550 kW. Tests under different load conditions show that at unit loads of 50MW, 70MW, 85MW, and 100MW, the variable frequency drive (VFD) speed regulation of the two induced draft fan systems reduces the overall input power by 471 kW, 506 kW, 472 kW, and 428 kW respectively compared to baffle regulation. Considering 6500 hours of annual unit operation, this translates to an annual electricity saving of 3.14 million kWh, a direct economic benefit of 880,000 yuan, and a payback period of 3.6 years. The relatively long payback period is mainly due to the relatively small capacity of the motor and the relatively high price of the VFD. 3. Condensate Pumps of Unit #6 (300MW) at Zhangjiakou Power Plant: After the condensate pumps of Unit #6 at Zhangjiakou Power Plant were converted to frequency converters, tests showed that the actual power consumption of constant-speed throttling regulation and frequency conversion regulation was compared. Based on an average operating time of 7000 hours, the annual power saving is approximately 4.08 million kWh. After deducting air conditioning power consumption, the annual power saving is 4.05 million kWh. At a grid connection price of 0.3 yuan/kW·h, the annual economic benefit is 1.25 million yuan, and the entire cost can be recovered in less than 3 years. Currently, the condensate pumps of Units #5, #6, #7, and #8 at Zhangjiakou Power Plant have all been converted to frequency converters. 4. Suction Fans of Unit #2 (125MW) at Douhe Power Plant: The suction fan motor capacity of Unit #2 at Douhe Power Plant has a capacity of 1000 kW and was put into operation after a minor modification in November 2002. During the tests, at unit loads of 90MW, 100MW, 110MW, and 125MW, the frequency conversion speed regulation of the two induced draft fan systems reduced the comprehensive input power by 571kW, 472kW, 489kW, and 520kW respectively compared to the damper regulation. This unit is a peak-shaving unit, frequently operating on a two-shift system. Based on an annual operating time of 5500 hours, the annual electricity savings are approximately 2.64 million kWh, resulting in direct economic benefits of approximately 860,000 yuan, with a payback period of approximately 2.8 years. 5. During the major overhaul in October 2002, the frequency conversion of the induced draft fan of Unit #3 (250MW) at Douhe Power Plant was carried out. Through testing, at unit loads of 126MW, 150MW, 175MW, 200MW, 225MW, and 250MW, the frequency converter speed regulation of the two induced draft fan systems reduced the comprehensive input power by 1048 kW, 1062 kW, 1052 kW, 872 kW, 694 kW, and 520 kW respectively compared to baffle regulation. Based on the current operating load of the unit, this translates to annual electricity savings of approximately 6 million kWh, resulting in direct economic benefits of approximately 1.6-1.7 million RMB, with a payback period of 2.6-2.8 years. 6. Induced Draft Fans of Boiler #3 (200MW Unit) at Xiahuayuan Power Plant: The induced draft fans of Boiler #3 at Xiahuayuan Power Plant underwent frequency converter modification during the 2003 major overhaul. Before the upgrade, the single power consumption of the induced draft fan was 3.2-3.4 kWh/t (steam). Since the overhaul, the single power consumption has remained at around 2.5 kWh/t (steam). Based on 7500 hours of operation per year, this translates to annual power savings of over 3 million kWh, with a payback period of 3.6-3.7 years. 7. Panshan Power Plant #3 Boiler (600MW Unit) Primary Air Fan: The primary air fan of Panshan Power Plant Unit 3 uses an AB Powerflex 7000 series dual PWM, transformerless input isolation current-type frequency converter, marking the first time this type of frequency converter has been used in the grid. Operationally, the power consumption rate of the #3 unit's primary air fan is 0.47%, a decrease of 0.17 percentage points compared to before the upgrade. Monthly power consumption is 650,000 kWh less than that of Unit #4 on average, resulting in annual power savings of approximately 6 million kWh. II. Economic Evaluation Methods for High-Voltage Variable Frequency Speed ​​Control Retrofits There are two main methods for evaluating the economic efficiency of high-voltage variable frequency speed control retrofit schemes: The first is the "Payback Period Method," which refers to the longest period during which the grid revenue and other economic benefits from adopting high-voltage variable frequency speed control will compensate for the equipment investment and installation costs. The scheme with the shortest payback period is the optimal scheme. Energy savings can be measured through a metering system, and other economic benefits can be calculated by comparing them with the revenue of similar retrofitted equipment. The advantage of this method is its intuitiveness and clarity, but its disadvantage is that it only reflects the ratio of initial investment to returns and cannot reflect the long-term economic efficiency of the scheme. Since the present value of operating and maintenance costs required throughout the entire service life is difficult to estimate, we currently use this method to calculate economic benefits. The second method is the "Present Value of Future Costs," which refers to the present value of the cost of purchasing additional equipment (high-voltage frequency converter), installation costs, and the operating and maintenance costs required to maintain the main and additional equipment throughout their entire service life. The scheme with the lowest total present value is the optimal scheme. This method comprehensively and accurately reflects the economic advantages and disadvantages of a scheme, but it requires detailed preliminary research and high accuracy in terms of original data and operating costs required throughout the entire service life. Otherwise, the calculation basis will be inaccurate, thus affecting the effectiveness of the economic evaluation. For the above reasons, this paper uses the "payback period method" to calculate the economic benefits. However, regardless of the method used, the economic benefits of variable frequency speed control for centrifugal fans and pumps are obvious, with a payback period of approximately 3-4 years. Other economic benefits of variable frequency drive retrofitting include reduced pollution emissions due to lower coal consumption for unit power supply; reduced energy consumption and reduced pipeline vibration due to fully open dampers during variable frequency speed control, resulting in smaller differential pressure fluctuations and improved boiler operation stability; smooth start-up for units operating on two shifts or frequently experiencing large peak loads reduces wear on motors and fans, lowers failure rates, and reduces maintenance costs; and the control and regulation characteristics of variable frequency speed control are better than damper regulation, making coordinated control easier to achieve. III. Major Problems Encountered During Operation: Several problems occurred during the installation, commissioning, and operation of the frequency converters. Please pay attention during use. These include: individual frequency converters experiencing burnt control modules or control board malfunctions; some frequency converters exhibiting high pulse overvoltages in the output voltage relative to ground; widespread high indoor temperatures in the commissioned equipment, sometimes even causing high-voltage auxiliary equipment to trip, requiring the installation of high-power air conditioning or ventilation systems; and some motors exhibiting shaft misalignment after frequency conversion (not present at power frequency). These problems are currently under further investigation and debugging. IV. Conclusion More and more countries and enterprises worldwide recognize that a sustainable society should meet its needs without jeopardizing the future of future generations. Therefore, every power generation company and power plant should fully recognize its social responsibility, taking energy conservation, improved energy efficiency, and reduced environmental pollution as the intrinsic driving force for sustainable and healthy development. With "energy conservation and consumption reduction, sustainable development" as the theme, they should continuously improve their awareness of energy conservation, resources, and the environment. Placing energy conservation on the agenda of leaders at all levels, relying on scientific and technological progress, promoting technological energy conservation, actively promoting new energy-saving technologies, materials, and processes, and supporting and encouraging the development and application of energy-saving technologies and products are powerful measures to achieve energy conservation results. Energy conservation and consumption reduction are eternal themes for every enterprise. Especially under market economy conditions, the lower the overall power generation cost for power generation enterprises, the better. Analysis based on this clearly shows that in some projects, saving electricity is more beneficial than saving coal. Reducing the power plant's electricity consumption rate brings greater economic benefits to both the power plant and society. Providing more electricity to society without consuming more coal is very beneficial for reducing power generation costs and environmental pollution. Especially after the separation of grid and power plants, the economic benefits to enterprises should be the basis for energy conservation analysis. Through scientific demonstration of energy conservation projects, priority should be given to developing energy-saving projects with good energy-saving benefits to create as much economic benefit as possible for enterprises.