Abstract: This paper discusses the performance characteristics and system principle of high-voltage frequency converters. It analyzes the application of high-voltage frequency converters in condensate pumps at Zhenjiang Power Plant from the perspectives of energy saving, high efficiency, and environmental protection. Keywords : High-voltage frequency converter, condensate pump, unit series connection [align=center]Figure 1: Simplified Process Diagram of Condensate System[/align] The parameters of the condensate pumps for Units #5 and #6 of Zhenjiang Power Generation Co., Ltd. are as follows: Condensate Pump Motor for Units #5 and #6: Motor Model: YKSL630-4; Rated Power: 2000kW; Rated Voltage: 6kV; Rated Current: 226.4 A; Rated Speed: 1489rpm; Power Factor: 0.89; Insulation Class: F; Quantity: 4 units; Electrical Control Method: DCS Centralized Control; Drive Method: Back-to-back Wheel Connection. Because the capacity of the motor used in the condensate pumps has a large margin, its energy consumption is relatively high. With the need for energy conservation and consumption reduction and the development of high-voltage frequency conversion technology, combined with the current operating status of the equipment, it was decided to carry out frequency conversion retrofitting on the condensate pumps of Units #5 and #6. The ZYQ-VERT-A2000/06 high-voltage frequency converter from Tianjin Yiqing Energy-Saving Electrical Equipment Co., Ltd. was adopted on Units #5 and #6. 2. Condensate Pump Operation Process and Variable Frequency Drive Retrofit Technology Scheme 2.1 Operating Conditions of Units #5 and #6 Adjusting the water level in the condenser is a major task in condensate pump operation. Under normal operating conditions, the water level in the condenser must not be too high or too low. When the unit load increases, the condensate flow increases, and the water level in the condenser rises accordingly. When the unit load decreases, the water level in the condenser decreases accordingly. Before using a variable frequency drive (VFD), the water level in the condenser was adjusted by changing the opening of the condensate pump outlet valve. This resulted in poor linearity and significant energy loss through the valve. Furthermore, frequent valve operations reduced valve reliability, affecting the stable operation of the unit. After using a high-voltage VFD, the condensate pump outlet valve no longer requires frequent adjustment. The valve opening remains within a relatively large range. By adjusting the output frequency of the VFD to change the motor speed, the outlet flow rate is adjusted to meet the requirements of the operating conditions. Units #5 and #6 are equipped with two 6kV/2000kW condensate pump motors. 2.2 Technical Upgrade Plan for Units #5 and #6 Without using frequency converters, the water level in the condenser is adjusted by changing the opening of the condensate pump outlet valve. This adjustment has poor linearity, resulting in throttling losses and wasted energy. Furthermore, frequent valve adjustments reduce valve reliability and affect the stable operation of the units. To further optimize the condensate pump operation and save energy, high-voltage frequency conversion upgrades are required for the condensate pump motors of Units #5 and #6. According to user requirements, the system will not be equipped with a bypass cabinet for the time being, and the frequency converter will have an interface with the high-voltage switchgear: ● Closing Interlock: The frequency converter's "closing permission" signal is connected in series with the high-voltage closing circuit. If the frequency converter fails or is not ready, closing the upper-level high-voltage switch (circuit breaker DL) is not allowed; ● Fault Tripping: The frequency converter's "high-voltage tripping" signal is connected in parallel with the high-voltage tripping circuit. When the frequency converter fails, the high-voltage input to the frequency converter is disconnected; ● Protection: The original motor protection and its settings remain unchanged. When the frequency converter malfunctions, the "high-voltage disconnect" switch closes, cutting off the high-voltage input power to the frequency converter. Simultaneously, the "closing permission" switch opens, preventing high-voltage input. If the standby unit is allowed to operate at this time, the system automatically puts the standby unit into operation at the mains frequency. Units #5 and #6 operate in a one-to-one configuration. Due to significant load variations during condensate pump operation, the adjustment speed needs to be fast, thus requiring the frequency converter to have overload capacity and overcurrent protection measures. In terms of control, the DCS sends a speed operation signal (4-20mA standard signal) to the frequency converter based on the unit load and deaerator water level; the frequency converter adjusts the pump motor speed according to the given speed signal. 3. Other Advantages of Condensate Pump Speed ​​Regulation Variable frequency speed regulation not only offers significant energy savings but also significantly improves system safety and reliability, offering the following advantages: ※ Reduced Current Impact During Motor Start-up: The maximum starting current of a direct-start motor is 7 times the rated current, 4.5 times for star-delta start-up, and 2.5 times for a soft starter. Variable frequency starting results in virtually no impact. * **Extending Equipment Lifespan:** Variable frequency speed control (VFD) prevents cavitation in the pump under low loads. Furthermore, VFD eliminates stress loads on the bearings, extending their lifespan. * **Improving Piping System Reliability:** VFD operation reduces the impact on the piping system caused by valve adjustments, thus lowering pump and system noise and improving the operating environment. 4. Conclusion Jiangsu Zhenjiang Power Generation Co., Ltd. is a thermal power generation enterprise established according to modern enterprise systems. In recent years, with the continuous advancement of power system reform and power marketization, the power industry has entered a new era. Seeking efficiency and development has become a prominent theme for power generation enterprises. Energy conservation is crucial to the profitability of power generation enterprises and has received high attention from all parties. Energy conservation is not only a need for enterprises themselves but also a common requirement of the nation and society. Environmental protection, energy conservation, and clean production are widely advocated; various new energy-saving technologies and products are constantly emerging, and energy conservation work has entered a new stage. At the same time, power generation enterprises face new coal market conditions and increasingly demanding peak-shaving tasks for the power grid, presenting new challenges to energy conservation work. Therefore, updating concepts, keeping pace with the times, and actively exploring new ideas for energy conservation are important foundations for improving corporate economic benefits and enhancing corporate competitiveness.