The frequency conversion electric actuator was first successfully developed abroad. The domestic applications were earlier in the petrochemical, mining machinery and other industries. The power industry initially used frequency conversion speed control from the powder feeder. This is because the powder feeder uses a low-voltage motor. Low-voltage frequency converters mature earlier, are simple to install, and it is easier to carry out frequency conversion transformations on motors. After the powder feeder adopts frequency conversion speed regulation, not only has it achieved significant economic benefits, but also has many advantages compared with the traditional mechanical speed control device: the powder feeder is evenly fed, the pulverized coal flow phenomenon is reduced, and the boiler combustion is stable; fuel The adjustment range of the control system is widened, and the protection function and accident handling capability are enhanced. Because of this, most power plants have successively carried out frequency conversion transformations on the powder feed motor and the coal feeder of the direct-blowing combustion system, and have achieved good operating results.
With the increasing maturity of high-voltage frequency conversion technology, high-voltage frequency conversion electric actuators have gradually begun to be used in the power industry. Taking into account the energy-saving effect, domestic equipment using high-voltage frequency conversion devices are mainly concentrated in blowers, induced draft fans, mortar pumps, low-pressure drain pumps, and risers. For pressurized water pumps and condensate pumps, there have been examples of using high-voltage frequency conversion devices on feed water pumps abroad.
For example, before there was no frequency conversion electric actuator, the thermal power unit always used the motor to run at a constant speed, and controlled the air volume of the boiler furnace by adjusting the opening of the guide vanes or baffles of the blower and induced draft fan. However, the supply and induced draft fans of units above 200MW use high-voltage and high-power motors, which consume a lot of power. The resulting throttling loss wastes a lot of factory power, which is very uneconomical, and the non-linear and slow response speed affect the automatic Invest in and adjust quality. Therefore, some old power plants have or are considering the use of variable frequency electric actuators to transform the air volume control method. Considering that the overall variable frequency electric actuator has many advantages, the transformation cost is high, and the original fan motor In terms of capacity level, protection level and other indicators, it can meet the requirements of frequency conversion speed regulation. Therefore, the frequency conversion device is added on the basis of retaining the original equipment. There are two methods: one method is to increase the frequency conversion device and the original electrical The control lines are connected in parallel, and the path to control the operation of the motor is selected through the switch, as shown in the figure. Using this method, when the frequency conversion device fails or is overhauled, the motor can be restored to the original control mode, without affecting the operation of the entire unit, but the two control channels need to be interlocked to avoid short circuits. The second method is to remove the original electrical control circuit and directly use the frequency converter to control the operation of the motor.
After adopting the above methods to transform the high-voltage electrical equipment with high energy consumption in the old unit, it not only improves the adjustment quality of the related control system, but also improves the stability and reliability of the control system, and more importantly, saves factory electricity. Therefore, more and more power plants are paying more and more attention. For example, Daqing Huaneng Xinhua Power Plant has carried out frequency conversion transformation on the induced draft fan and mortar pump; Anhui Tongling Power Plant has carried out frequency conversion transformation on the low-heat drain pump; Qinghe Power Plant has carried out frequency conversion transformation on the induced draft fan. After the transformation, good economic and social benefits have been achieved.
