Foreword The Yongan Thermal Power Plant has a total of 6 units with a total installed capacity of 350MW. The 6 boilers all burn Fujian anthracite and heavy oil is needed for combustion. To this end, the crude oil storage of Yongan Thermal Power Plant is equipped with three fuel pumps, including one small pump and two large pumps. The relevant parameters are shown in Table 1. They are responsible for continuously supplying heavy oil to the boiler combustion. With the decommissioning of 25MW units and the rapid development of Fujian Electric Power, there is a serious surplus of power, which makes the units of our plant start, stop and peak-shave very frequently, and usually only one or two units are operated in the whole plant. There is also a serious surplus in the output of the oil pump, making the outlet pressure of the oil pump a prominent problem. The increase in oil pressure will cause the boiler to increase the fuel consumption of the fuel, and the long-term operation of the oil pipe under the pressure of the oil pipe can easily lead to tube explosion. In this regard, pressure reduction measures must be taken. Due to the high oil temperature at the outlet of the oil, the throttling method of closing the outlet of the oil pump will cause the oil pump to vaporize and lose pressure. This method is not desirable. At present, only measures to return oil from the oil pump outlet mother pipe, that is, from the oil pump outlet mother Connect the return pipe of the oil return valve to the oil depot. This method greatly increases the power consumption of the oil pump, causing unnecessary waste, and the economic losses caused by the accumulation of time are huge. Therefore, Table 1 is urgently needed for the related parameters of the fuel pumps in the crude oil depot of Yongan Thermal Power Plant. Water pump factory supporting motor Jiamusi Motor Factory takes effective measures to improve the operating efficiency of the oil pump, reduce power consumption, and save energy.

Our factory successfully solved the problem of high oil pressure through frequency conversion technology transformation of the fuel pump, and achieved the purpose of energy saving and consumption reduction.

1. Plan determination In the past ten years, with the rapid development of power electronic technology and microelectronic technology, frequency conversion technology has gradually matured from theory to practice. The principle of the variable frequency speed regulator is to change the synchronous speed of the AC motor smoothly by changing the stator power supply frequency uniformly, and the motor speed is proportional to the frequency to achieve the purpose of continuous adjustment of the motor speed. At present, the variable frequency speed regulation technology is gradually occupying a dominant position in various AC and DC speed regulation systems due to its advantages of high efficiency, large speed regulation range, high speed regulation accuracy, soft start characteristics, stepless speed regulation and so on. After technical analysis, it is confirmed that the frequency converter is also suitable for application in fuel pumps.

The application of variable frequency speed regulator to the constant pressure control of fuel pressure constitutes the constant pressure fuel supply system of the inverter.

2 Scheme implementation 2.1 Equipment selection This project is installed by M Menxin Lujia Industrial Automation Co., Ltd. According to the technical requirements of our factory, the inverter uses FRN110G9S type of Japan Fuji, and the pressure transmitter uses the products of American HoneyWell company with high temperature resistance, explosion-proof and other properties.

2.2 Renovation plan Because the power supply of No. 1 and No. 2 fuel pumps of our plant is connected to the same section of the factory power bus, in order to improve the reliability of safe operation, it is selected to install variable frequency speed regulators on the motors of No. 2 and No. 3 fuel pumps. . In order to reduce costs, through the design of the circuit, the function of sharing a frequency conversion speed regulation base for No. 2 and No. 3 fuel pumps has been realized. Under normal circumstances, the No. 3 (or No. 2) fuel pump is running, and the No. 2 (or No. 3) fuel pump is on standby. When the inverter is out of operation or the fault is overlooked, the bypass power supply is automatically turned on. If No. 3 (or No. 2) fuel pump or motor fails, the inverter can be switched to No. 2 (or No. 3) fuel pump or motor. Improve the reliability of the inverter and fuel pump operation. No. 1 fuel pump is used as a backup for No. 2 and No. 3 fuel pumps during maintenance or faults to ensure that the oil system continuously supplies oil to the boiler. The original fuel system remains unchanged during system modification.

3 Inverter constant pressure control principle The pressure transmitter installed in the oil outlet pipe h detects the change in oil consumption through the change in pipeline pressure, and transmits it to the PID regulator, by comparing the set constant pressure value with HD After the signal value of 420rriA is output to the inverter, if the pressure is high, the output frequency is reduced, and if the pressure is low and wide, the output frequency is increased, so that the oil supply amount can be adjusted by controlling the speed of the oil pump motor, so that the oil supply pressure is always stable. Within the range allowed by the constant value, and ultimately achieve the purpose of improving the quality of fuel supply and high efficiency and energy saving.

4 Advantages and Disadvantages The constant pressure oil supply system of the inverter is a widely used AC speed regulation method at present. Since the system has been put into operation, it has stable operation and good performance, and has the following outstanding advantages: soft start characteristics . Originally using full pressure to start the oil pump motor, the starting current reached 4~7 times its rated current. After starting with an inverter, the starting current is only 50% 90% of the rated current. It has A-motion control function. The system uses closed-loop automatic control.

The outlet pressure of the fuel pump can be kept within a stable value regardless of the change in the amount of oil used by the boiler, thereby achieving constant pressure control of the fuel pressure.

Simple operation and reliable operation. Inverter equipment C1 is very dynamic. When there is a problem with the sensor, the pressure can be adjusted by the person to ensure that the oil supply system is constantly oiled.

Perfect protection function. Inverter. There are protection functions such as under-voltage, over-E, over-current, overload, short circuit and overheat. From the above, the frequency converter changes the motor speed by changing the frequency.

From time to time to adjust the size of the output and keep the hydraulic pressure constant H. During operation, it is found that when the frequency drops to 35Hz to F, the motor heating phenomenon is more serious. This is because the ordinary motor is used for frequency conversion speed regulation. When the frequency is low, the motor ventilation rate is reduced due to the low speed, resulting in difficulty in heat dissipation As a result of the sharp increase in the temperature rise of the motor, the lower limit of frequency conversion should be set to control the operation of the fuel pump. Its frequency limit above 35Hz is sufficient for use. If it is used in other systems and needs to use a lower frequency, the motor can be equipped with ventilation equipment or a variable frequency motor with a wide speed range, strong overload capacity, and low speed performance.

5 Benefit analysis 5.1 Direct economic benefit analysis The motor power of No. 2 and No. 3 fuel pumps are the same, both are 100kW, and the rated current is 175A. The average operating current of the pump is 137A before using variable frequency speed regulation, and after using the inverter The actual average operating current is 60A, the power supply voltage is 380V, and the motor power factor is generally 0.85. The active power consumed is calculated as follows: after changing to frequency conversion speed regulation: this is the case. Electricity: jealous = (brother-P2) xA total investment of this frequency conversion technology transformation is 100,000 yuan. In this way, the investment cost can be recovered within 18 months.

5.2 Analysis of Indirect Economic Benefits Due to the soft start function of the inverter, the starting current of the motor is small, which can better protect the motor, extend the service life of the motor, and reduce maintenance funds.

The closed-loop automatic control system is used to stabilize the oil pressure of the oil supply, which can not only ensure the stability of the boiler's combustion conditions, ensure the safe operation of the boiler, but also control the boiler's oil pressure to operate at a lower limit, saving oil. After adopting the frequency converter, there is no need for the operator to adjust the return valve frequently. When the pressure needs to be changed, as long as the setting value is changed, the requirements can be met, the operation is simple, and the labor intensity of the worker is reduced.

Because there is very little oil return, the loss and leakage of the oil circuit are reduced, and the maintenance and management costs are reduced, and the economic benefits are more considerable.

6 Conclusion The use of high-tech products such as inverter constant pressure oil supply system has very practical significance for improving labor productivity, saving energy and reducing consumption, improving equipment operation reliability, stability, and extending equipment life. In the power industry, there are still many devices that need to be installed with a constant voltage control system for frequency converters, which is also the trend of future development.