I. Introduction The heat dissipation and operating environment of equipment in high-voltage frequency converter applications directly affect the operational safety of the frequency converter itself. With the continuous increase in frequency converter power, the investment and operating costs of its auxiliary cooling are receiving increasing attention. Adopting professional high-voltage frequency converter-specific cooling to improve equipment safety and stability, and reduce the operating costs of the auxiliary cooling system, has become one of the important issues to consider in high-voltage frequency converter applications. The following is a comparative analysis of the economic indicators of common room air conditioning cooling and dedicated high-voltage frequency converter cooling systems. II. Economic Analysis of Air Conditioning Cooling 1. Cooling Power Calculation Taking the cooling of the high-voltage frequency converter of the primary air fan of a 350MW unit in a Huaneng power plant as an example. The two primary air fan high-voltage frequency converters have a power of 1600kW each and are installed in the same high-voltage frequency converter room. The building area is 9m × 6.5m × 4.5m (length × width × height). Based on the southern climate, 180W of cooling capacity is required per square meter, so the building's self-cooling loss is: 2. Calculation of Air Conditioning Cooling Power Consumption III. Economic Analysis of Air-Water Cooling System 1. The cooling power calculation above shows that the rated heat output of two 1600kW high-voltage frequency converters is 128kW. When using an air-water cooling system, the system achieves heat exchange of all the hot air discharged from the high-voltage frequency converters through the air-water cooling device, and then returns the cool air to the room. Therefore, its airflow circulation efficiency is greatly improved, approaching 99%. Unlike air conditioning, which cools the room before cooling the equipment, the latter achieves environmental control of the high-voltage frequency converter room by absorbing the heat generated by the equipment. Its system efficiency is naturally improved, and it avoids the consumption of cooling capacity required for ambient cooling. Considering the heat output under extreme operating conditions, as well as factors such as high water temperature and system exchange efficiency, the design margin of the air cooler is usually selected as 1.15 to 1.2 times. That is, the heat exchange power of the air cooler should not be less than 73.6kW/unit, and the actual selected air cooler power is 75kW per unit. 2. The power consumption of the air-cooling system for each high-voltage frequency converter is calculated as follows: The main power-consuming equipment is a 2.2kW booster fan. This equipment, along with the fans on the top of the high-voltage frequency converter cabinet and the fans configured in the air-cooling system, operates in a hot standby configuration. The system adopts an indoor closed-loop circulation cooling system, with the ambient temperature controlled below 40℃. When the primary air fan uses the air-water cooling system to achieve ambient temperature control, the total power consumption of the fan配套 (matched) with each high-voltage frequency converter is 2.2kW, and the power consumption of the cooling fans for two high-voltage frequency converters is 4.4kW. Since this system utilizes the unit's closed-loop industrial cooling water for heat exchange, the cooling water is recycled, with a circulating water requirement of 36t/h per unit. Based on the total circulating water volume of the units operating on-site, the water usage ratio of this primary air system is less than 2% of the total, therefore the increase in circulating pump power consumption is very small and can be ignored. The total power consumption per unit using the air-water cooling system is 4.4kW. The daily power consumption of the high-voltage inverter room for the primary air fans of the two units operating under air-water cooling is 24 × 4.4 = 105.6 kWh. Based on an annual effective operating period of 210 days and an electricity price of 0.37 yuan/kWh, the annual power consumption for cooling the high-voltage inverter room for the primary air fans is 22,176 kWh, equivalent to 8,200 yuan. Assuming a cost of 97,000 yuan per 75kW air-water cooling system, the total investment for air-water cooling equipment is 194,000 yuan. IV. Economic Comparison Analysis Based on the above data, the economic comparison analysis between the air-water cooling system and conventional air conditioning cooling is as follows: V. Conclusion The adoption of an air-water cooling system for the high-voltage inverter room of the primary air fans in a 350MW power plant of Huaneng Group, in addition to bringing direct energy-saving economic benefits, will also bring the following economic benefits: 1. After adopting the new cooling system, the equipment cooling operating cost of the high-voltage inverter will be reduced by about 90% compared to conventional air conditioning cooling. 1. Operating costs are only one-tenth that of air conditioning cooling systems. 2. Because the new cooling systems all adopt a closed-loop cooling structure design with circulating airflow, they feature low dust levels, environmental stability, and minimal susceptibility to external environmental factors. The cleaning cycle of dust filters can be extended from the original 7-15 days to 30-45 days, significantly reducing the workload of maintenance personnel. 3. Due to the reduced number of devices used and in operation, and because the air-water cooling system is primarily composed of mechanical equipment, its stability and safety are far superior to the power electronic equipment used in air conditioning refrigeration. System safety is improved, ensuring the safe operation of the unit from the perspective of auxiliary equipment. 4. The new cooling system is designed with full consideration of safety protection measures such as equipment failure, heat exchange medium leakage, emergency bypass of airflow, ease of operation, and maintainability. Integrated operation with high-voltage frequency converter equipment improves overall safety performance. 5. The service life of the air-water cooling system is 5-8 times that of air conditioning equipment, thus significantly reducing equipment maintenance costs. In conclusion, the adoption of an energy-saving and environmentally friendly air-water cooling system in the primary air turbine frequency converter energy-saving project of a Huaneng power plant is both necessary and feasible. The project demonstrates significant economic advantages and deserves widespread promotion in the high-voltage frequency converter application industry, thereby achieving comprehensive energy savings in high-voltage frequency converter projects. Reference: "Comparison of Two Cooling Methods for High-Voltage High-Power Frequency Converters," *Frequency Converter Communications*, Issue 6, 2007, Liu Junxiang.