Application of High Voltage VFD (Variable-frequency Drive) in Blower

The thermal power plant has reduced the energy loss of the equipment, improved the production efficiency, and achieved considerable social and economic benefits through the frequency conversion transformation of the high-pressure blower. The original operation mode of the blower is step-down start and power frequency operation, and its air volume is also adjusted by adjusting the damper. The disadvantages of this control method are large waste of electric energy, large waste of fuel, poor real-time adjustment, high noise, and high labor intensity for workers. With the adjustment of power generation load in a wide range, the air volume of the blower is often in a state due to the change of boiler load. In low efficiency state, a lot of energy is wasted on the air duct baffle. In recent years, with the rapid development of high-voltage frequency conversion technology, frequency conversion transformation of boiler drums and induced draft fans has been widely used. Through market research, we introduced Sunwoele's HFV3000 series high-voltage VFD (Variable-frequency Drive), which uses advanced power electronic devices IGBT and multi-level topology circuits and PWM modulation strategies, controlled by high-speed digital signal processor DSP, can After the power conversion of the 3000~10000 volt three-phase AC power system with fixed frequency and amplitude, a high-voltage AC system with adjustable frequency and current depending on the load is generated, so that the continuous speed regulation of the three-phase motor can be realized.

Estimation of energy saving: Before the transformation, the current of the blower is about 30A, and the opening of the fan baffle is between 60~70%. After the transformation, the current of the blower is reduced to 20A, which is reduced by 1/3, and the opening of the baffle is 100%. . The operating conditions are based on 24 hours of continuous operation and 300 days of annual operating time as the calculation basis, then the annual power saving during frequency conversion speed regulation is P=1.732×6×10×0.95×24×300=710812kW?h. Calculated at 0.48 yuan per kilowatt-hour, the electricity bill can be saved by about 341,190 yuan per year.

Other effects produced by the application of high-voltage frequency conversion speed regulation system: the process is improved. After the VFD (Variable-frequency Drive) is put into use, the dust removal fan can adjust the air volume very smoothly and stably, and the operator can control it freely. The operating parameters of the dust removal fan have been improved and the efficiency has been improved.

Extend the service life of motors and fans. Generally, the dust removal fan is a centrifugal fan, which has a long start-up time and a large start-up current (about 6 to 8 times the rated current), which has a great mechanical impact on the motor and fan, seriously affecting its service life. After adopting frequency conversion speed regulation, soft start and soft brake can be realized, and there is almost no impact on the motor, which can greatly prolong the service life of the machine.

Reduce wear on valve machinery and fan impellers. After the installation of frequency conversion speed regulation, the fan often works at a speed 150 rpm lower than the original fixed speed, so the wear of the fan impeller is greatly reduced, and the vibration of the fan is reduced. Extend the overhaul period of the fan and save maintenance costs and time.

It is convenient to realize the automation of the dust removal control system. The air volume of the dust removal system often needs to be changed according to the requirements of the process. In the past, when the baffle was used to adjust, there was a problem of the linearity of the relationship between the opening of the actuator and the flow rate. Often due to the excessive wear of the actuator, the characteristics of the valve change, and nonlinear problems occur, resulting in errors in the adjustment process and automatic control systems that cannot work normally. The frequency conversion speed regulation always works within the range of linear high precision 0.1 ~ 0.01HZ, creating favorable conditions for realizing the automation of the dust removal system.

Through the technological transformation of the blower, our factory has improved production efficiency, and the economic and social benefits are considerable. In the future, we will further strengthen the technical transformation work and build our factory into a high-tech, high-efficiency modern power plant.