Abstract : This paper introduces the application of domestic high-voltage frequency converters in the dust removal air blowers of the sintering plant of Jinan Iron and Steel Corporation. The on-site operation of the frequency converters shows that the adoption of domestic high-voltage frequency converters for speed regulation and energy saving of the batching dust removal air blowers in the metallurgical industry is successful, and the energy-saving effect is obvious. Keywords : High voltage frequency converter, energy saving 1. Introduction Jinan Iron and Steel Corporation was founded in 1958 and is one of the top ten steel mills in China. It is the largest producer and exporter of medium and heavy plates in the country, ranking among the top in the country in terms of product export ratio, output of medium and heavy plates, cost, market share, and export volume. The sintering plant of Jinan Iron and Steel Corporation has 4 sintering machines with an annual output of 5.8 million tons of sintered ore. All raw materials and finished products are transported via belt conveyors, generating a large amount of dust during transport. This dust causes environmental pollution and requires dust removal treatment according to national regulations. The electrostatic precipitator at Jinan Iron and Steel Group's sintering plant is responsible for dust removal from the flux crushing system and the flux area of ​​the batching room. Because the flux crushing system operates intermittently, the batching dust removal system experiences high dust concentrations and requires large air volumes for approximately 70% of the day, while the remaining 30% of the day has relatively low dust levels and does not require a large air volume. However, the existing system regulates air volume by adjusting the damper at the fan inlet, resulting in the fan motor always running at full load, leading to unnecessary energy waste. With the increasing intensity of the market economy, energy conservation and consumption reduction have become effective means for enterprises to improve product market share and competitiveness. The increasing maturity of high-voltage, high-power variable frequency speed control technology has led to its widespread application in various industries such as metallurgy, petroleum, chemical, power, cement, water supply and drainage, pharmaceuticals, papermaking, and sewage treatment. It is under these circumstances that Jinan Iron and Steel Group's sintering plant is conducting research on high-voltage variable frequency technology for its batching dust removal system . Equipment Overview The dust collector fan motor in the Jinan Iron and Steel Sintering Plant is a 200KW high-voltage asynchronous motor manufactured by Shenyang Electric Machinery Co., Ltd. The main parameters of the unit are as follows: Dust Collector Fan Parameters: Model Y4-73; Air Volume 145000m³/h; Air Pressure 4000Pa. Motor Parameters: Model YKK3554-6; Rated Power 200KW; Rated Voltage 6000V; Rated Current 24A; Rated Speed ​​985rpm. 3. High-Voltage Variable Frequency Speed ​​Control System The upgrade uses the Fengguang brand JD-BP37-240F power unit series multi-level high-voltage high-power frequency converter manufactured by Shandong Xinfengguang Electronic Technology Development Co., Ltd. The following is an introduction to the Fengguang brand JD-BP37-240F high-voltage frequency converter. 3.1 Main Performance Indicators of Fengguang JD-BP37-240F High-Voltage Frequency Converter: Frequency Converter Power: 240KW; Rated Output Current: 32A; Input Frequency: 50HZ±5HZ; Rated Input Voltage: 6KV; Allowable Voltage Fluctuation: ±20%; Input Power Factor: ≥0.98; Output Frequency Range: 0～50HZ; Output Voltage Range: 0～6KV; Frequency Resolution: 0.01HZ; Acceleration Time: Can be set by user's production process; Deceleration Time: Can be set by user's production process; Frequency Converter Efficiency: ≥96%; Overload Capacity: 100% continuous, 160% continuous for 1 minute, 220% allowable for 1.5S; Protection Class: IP20. 3.2 Main Technical Performance of JD-BP37-240F High-Voltage Variable Frequency Speed ​​Controller: 3.2.1 High-Voltage Source Type Frequency Converter: Direct 6KV Input, Direct 6KV Output, No Need for Any Output Transformer or Filter, Suitable for Ordinary High-Voltage Motors, No Damage to Motor or Cable Insulation. 3.2.2 High input power factor and low current harmonics, eliminating the need for power factor compensation and harmonic suppression devices. 3.2.3 Modular design of unit circuits, simple maintenance, and good interchangeability. 3.2.4 Output stepped sine PWM waveform. 3.2.5 Fiber optic connection between the high-voltage main circuit and the controller, ensuring strong and weak current isolation and safety. 3.2.6 Comprehensive fault detection, precise fault protection, and accurate location display and alarm. 3.2.7 Built-in PLC, easy to modify control logic, flexible selection of on-site/remote control to adapt to changing on-site needs. 3.2.8 Utilizes carrier phase-shift control technology, significantly suppressing harmonic components of the output voltage and ensuring a perfect sine wave output waveform. 3.2.9 The control power supply is independent of the high-voltage power supply; the inverter output can be detected even without high voltage, facilitating on-site debugging, operator training, and maintenance. 3.2.10 Employs quasi-optimized SPWM modulation technology for high voltage utilization. 3.2.11 The power unit undergoes 24-hour high-temperature aging and 150% load testing, ensuring high reliability. 3.2.12 It features a Chinese Windows operating interface and a color LCD touchscreen. The user operation and monitoring system interface is very user-friendly and comprehensive, including a host computer (commercial PC), a slave computer (industrial control computer), and a microcontroller. The microcontroller provides users with a 4-digit LED digital display and a 12-key keypad operating platform, enabling full operation of the inverter, including parameter settings and various operating commands. The industrial control computer provides a user operating platform using a touchscreen and a universal keyboard, offering more complete functions, including parameter setting, function setting, operation, operating data printing, fault query, etc. The host computer (commercial PC) is located in the central control room and can remotely measure and control multiple inverters. If there is only one inverter, the host computer can be omitted or customized by the customer. 3.2.13 It can receive and output multiple industrial standard signals. 3.2.14 It can print out operating reports. 3.3 The Fengguang brand JD-BP37-240F high-voltage variable frequency speed control system adopts a direct "high-high" conversion method, belonging to the voltage source type. It uses a multi-level series connection of power units, with the new Siemens IGBT as the main control device. It features fully digital control and a color LCD touchscreen control, and is a high-quality variable frequency speed controller designed for high reliability, ease of operation, and high performance. It has low harmonic pollution to the power grid, with input current harmonic distortion less than 1%, directly meeting the IEEE 519-1992 harmonic suppression standard. It has a high input power factor, eliminating the need for input harmonic filters and power factor compensation devices. The output waveform quality is good, without problems such as additional motor heating, torque pulsation, noise, output dv/dt, and common-mode voltage caused by harmonics. It eliminates the need for an output filter and can be used with ordinary asynchronous motors. The wind and solar high-voltage frequency converter uses several low-voltage inverter power units connected in series to achieve direct high-voltage output. The 6kV high-voltage frequency converter used has 18 sets of secondary windings in the transformer, which are divided into 6 power units/phases, for a total of 18 units in three phases. It adopts 36-pulse rectification, and the harmonic components at the input end are far lower than the national standard. The system structure of the high-voltage frequency converter is shown in Figure 1, and the main circuit of the unit circuit is shown in Figure 2. The bypass branch uses a thyristor module. 3.4 System functions (1) Unit bypass function When a power module fails, it automatically bypasses and runs without stopping the frequency converter, but it needs to be derated. That is, a bypass circuit is connected in parallel between the output terminals of each power unit. When a power unit fails, the trigger signal of the corresponding power unit IGBT is blocked, and then the bypass SCR is turned on to ensure that the motor current passes through and a path is still formed. In order to ensure the symmetry of the three-phase output voltage, while bypassing the faulty power unit, the other two corresponding power units are also bypassed at the same time. (2) Protection Functions: The frequency converter has protection functions against overvoltage, undervoltage, overcurrent, phase loss, frequency converter overload, frequency converter overheating, and motor overload. ① Overcurrent Protection: 160% of the motor current is allowed for 1 minute; if exceeded, protection will be activated immediately. ② Overload Protection: 120% of the motor current is allowed for 1 minute every 10 minutes (inverse time characteristic); if exceeded, protection will be activated. ③ Unit Overvoltage Protection: The DC bus voltage of each unit is detected; if it exceeds the set value, the frequency converter will perform overvoltage protection. ④ Unit Undervoltage Protection: The DC bus voltage of each unit is detected; if it is lower than the set value, the frequency converter will perform undervoltage protection. ⑤ Frequency Converter Overheat Protection: Temperature detection elements are placed on the input-side rectifier transformer and power unit; if the temperature limit threshold is exceeded, the frequency converter will perform overheat protection. ⑥ Phase Loss Protection: Phase loss is divided into input-side phase loss and output-side phase loss. There is a corresponding detection circuit; after phase loss, corresponding protection will be implemented. 3.5 Handling Common Problems The Fengguang JD-BP37-240F high-voltage frequency converter boasts a high level of intelligence and a comprehensive fault detection circuit, providing precise location for all faults and clear instructions on the industrial control computer interface. Users can take corresponding measures based on the fault information displayed on the industrial control computer. To ensure equipment reliability and maximize uninterrupted operation, the following faults will be handled as general faults: slight transformer overheating, cabinet door interlocking fault, unit cabinet fan fault, and industrial control computer fault. The system will not remember general faults. If such faults occur during system operation, the frequency converter will not shut down but will only issue an alarm. Even when stopped, users can still perform startup operations if such faults exist. The following faults will be handled as serious faults: unit serious faults and severe transformer overheating. The system will remember these serious faults. Once a fault occurs, the system will alarm and automatically trip and shut down. The system can only be restarted after the fault has been completely resolved. 4. System Modification Plan The main circuit of the modification plan for the batching and dust removal fan motor in the Jinan Iron and Steel Sintering Plant is shown in Figure 3 below: K0 User's original high-voltage switches K1, K2, and K3 Variable frequency drive bypass switch cabinet High-voltage disconnect switch BPQ JD-BP37-240F High-voltage variable frequency drive M High-voltage motor The variable frequency drive controls the batching and dust removal fan in a one-to-one control configuration. The bypass switch cabinet is used for industrial/variable frequency switching. K1, K2, and K3 are three high-voltage disconnect switches. K2 and K3 cannot be closed simultaneously; mechanical interlocking is required. When K3 is open and K1 and K2 are closed, the fan operates at variable frequency; when K1 and K2 are open and K3 is closed, the fan operates at industrial frequency. 5. Project Implementation Status On May 6, 2005, Jinan Iron and Steel and Shandong Xinfengguang Electronic Technology Development Co., Ltd. officially signed a supply contract and technical agreement for the variable frequency drive. On June 3, 2005, the variable frequency drive arrived at the sintering plant warehouse. From August 21 to 25, 2005, the inverter body was installed. On August 26, 2005, the inverter was tested under no-load conditions. From August 27 to 28, 2005, the inverter was tested under load. From August 29 to September 3, 2005, the inverter was tested under trial operation. On September 9, 2005, the inverter was officially handed over, and our company issued an acceptance report. 6. On-site operation status Compared with the original system, the high-voltage inverter produced by Shandong Xinfengguang Electronic Technology Development Co., Ltd. has the following advantages: (1) Stable operation and reliable safety. Since its official commissioning, the inverter has been operating continuously without faults. It only needs to be cleaned regularly, without stopping the machine, thus ensuring the continuity of production. (2) The fan speed can be adjusted by the inverter according to the actual dust concentration at the production site to achieve the purpose of dust removal and energy saving. (3) Reduced maintenance costs. Because the motor achieves true soft start and soft stop, the starting impact on various equipment such as motors, fans, baffles and the power grid is greatly reduced, reducing equipment maintenance, extending equipment service life and greatly reducing maintenance costs. (4) Reduced labor intensity of on-duty personnel. The original batching dust removal system has multiple operable valves. When running at the power frequency, in order to adjust the air volume and meet process requirements, the valves need to be adjusted frequently, which is cumbersome for on-duty personnel. After the frequency conversion, all valves are always in the open position. When the air volume needs to be adjusted, it is only necessary to adjust the operating frequency of the frequency converter remote control box in the duty room, which greatly reduces the workload of on-site personnel and improves work efficiency. (5) The frequency converter has multiple protection functions, which are very complete. Compared with the original old system, the frequency converter has multiple protection functions such as overcurrent, short circuit, overvoltage, undervoltage, phase loss and temperature rise protection, which protects the motor more accurately. (6) Significant energy saving effect, greatly reducing dust removal power consumption. To evaluate the effectiveness of the frequency conversion retrofit of the dust removal system, measurements and data analysis were conducted on the actual equipment usage and energy savings after the system was put into normal operation. The operating conditions were the same before and after the frequency conversion retrofit. On a randomly selected normal working day, the system was switched to power frequency operation with valve-regulated airflow and grid-side metering of power consumption. Then, the system was switched to frequency conversion operation, and power consumption was measured again. Specific data are shown in the table below. The table shows the following conclusions: After the frequency conversion retrofit, the daily power consumption of the dust removal system decreased by 2376 kWh compared to before, achieving a power saving rate of up to 46%, demonstrating significant energy-saving effects. 7. Conclusion In summary, the retrofit of the JD-BP37-240F high-voltage frequency converter produced by Shandong Xinfengguang Electronic Technology Development Co., Ltd. on the batching dust removal fan in our sintering plant was successful. It not only met the production process requirements of the batching dust removal system and achieved significant energy savings, but also demonstrated stable performance and reliable operation. In today's increasingly energy-constrained world, we believe that Fengguang high-voltage frequency converters will perform even better in more industries. References [1] Shandong Xinfengguang Electronics User Manual [Z]. Shandong Xinfengguang Electronics Technology Development Co., Ltd. [2] Shandong Xinfengguang Electronics JD-BP37-240F High Voltage Variable Frequency Speed ​​Control System Jinan Iron and Steel Commissioning Outline [3] Shandong Xinfengguang Electronics JD-BP37-240F High Voltage Variable Frequency Speed ​​Control System Jinan Iron and Steel Acceptance Report.