1.Overview



At present, the world is troubled by the energy shortage, China's energy situation is particularly severe. In the face of such a reality, the country has a series of countermeasures, so it promulgated the "Energy Conservation Law", and called on the whole society to build a resource-conserving society. Energy saving transformation is one of the effective ways, there are many aspects of energy saving transformation, among them, through the high voltage and high power motor frequency conversion speed regulation to achieve energy saving, is undoubtedly the greatest potential of energy saving. With the increasing maturity of high voltage and high power frequency conversion technology, it is possible to apply this technology in high power water pump in water plant. It is under this situation that the water supply and drainage plant of Sinopec xx Co., Ltd. studies and transforms the high voltage frequency conversion technology of the water pump equipment.

2. Implementation plans



Sinopec Co., Ltd. is known as the pearl of Sinopec and is well known in Shandong province. petrochemical water supply and drainage plant for the company's water supply system, xixia water distribution station is one of the subordinate units of water supply and drainage plant, day design water supply capacity of 200000 tons, clear water pump room is equipped with five pump unit, unit power is 550KW / 6 KW, transform all constant speed before running, the water size by changing the size of the valve opening adjustment. The purpose of controlling the water pump: to keep the hydraulic pressure of the frequency converter constant; Under the maximum opening of the pump outlet, change the output frequency through the frequency converter to adjust the water supply at the speed to change the water supply; to reduce the impact of the pump start and stop on the pipe network.

After multiple investigations and the cost performance, Petrochemical water supply and Drainage Plant decided to choose the FGI FD5000 series high voltage inverter produced by FGI Science And Technology Co., Ltd., for the speed regulation transformation of the 2 # and 4 # pump units of Xixia water distribution station. After the cooperation of the technical personnel of both sides, the frequency conversion transformation plan of the pump unit was jointly formulated. The field equipment diagram is shown in Figure 1 below. The transformation scheme adopts the form of one area 2, that is, the high voltage frequency converter drags any unit of 2 # and 4 # of the water distribution station. When one of the units is faulty or repaired, the frequency converter drags the other unit for frequency conversion operation. Units 2 # and 4 # of water distribution station are of the same type, and the main parameters of motor and pump of 2 # unit are as follows:

petrochemical water supply and drainage plant decided to choose FGI FD5000 high voltage frequency converter one drag two control system to 2 #, 4 # water pump units for speed regulation transformation.

FGI FD5000 high voltage frequency converter it is a full digital AC high voltage frequency converter control device, using advanced power unit series carrier shift phase technology, sine wave PWM modulation method, full Chinese operation interface, with high reliability, superior performance, easy operation and other characteristics, the specific design requirements are as follows:

(1) The system efficiency is high. Under the rated working condition, the total efficiency is above 96%, and the partial efficiency of the frequency converter is greater than 98%.

(2) The input side is 36 pulse rectification, and the harmonic voltage and harmonic current content of the power grid caused by the frequency converter meet the technical requirements of IEEStd519-1992 and GB / T14549-93 "Harmonics of Power Quality Public Power Grid".

（3) The rated input power factor of the frequency converter is greater than 0.96, without the power factor compensation device.

(4) The inverter output harmonic content is low and can drive ordinary high voltage motor without increasing the motor temperature rise and reducing the motor capacity, the motor cable has any length limit; protect the motor insulation from the damage of dv / dt stress; the service life of the equipment is not reduced due to the harmonic torque.

(5) It has the function of unit bypass. When a unit fails, the system can automatically bypass it and continue to operate to ensure the reliability of the system.

(6) Full Chinese operation platform, 10.4-inch real color LCD display, touch screen direct operation, more suitable for the use of Chinese habits.

(7) The modular structure of the power unit is interchangeable and easy to maintain.

(8) The input voltage range is wide and can be operated continuously within 6KV (± 20%).

(9) The power unit is controlled by optical fiber communication, completely electrical isolation, and has strong anti-interference.

(10) Built-in PID regulator, which can realize closed-loop operation.

(11) Built-in PLC enables flexible control of different application sites.

3.Application advantage

The FGI FD5000 high voltage frequency converter was successfully tested and passed the acceptance of Petrochemical water supply and drainage plant. The FD5000 high voltage frequency converter ran well. From the perspective of the application effect of the frequency converter in operation, the purpose of the pump has been fully achieved, and its advantages before the transformation are reflected in:

(1) Easy to operate and easy to observe.

All the data and operation status of the inverter can be displayed on the display screen of the upper computer, such as operating frequency, input voltage, input current, output voltage, output current, open closed loop, pressure value, etc. The upper computer display screen operation is simple and clear, easy to observe.

(2) The frequency converter operates stably and has good performance.

Since the FGI FD5000 high voltage frequency converter is put into operation, the operation is stable, the speed adjustment is smooth and reliable, the voltage and current are normal, and no abnormal phenomenon occurs.

(3) Reduce the labor intensity of the personnel on duty.

Because the frequency converter has the valve linkage function, with the change of water supply, the personnel on duty through the microcomputer remote monitoring system on duty, no longer need to frequently open and stop pumps and valves, the workload is greatly reduced.

(4) Constant pressure control.

The pressure closed-loop constant pressure control is adopted. The user only needs to set the required pressure according to the actual water supply needs. The frequency converter automatically runs with constant pressure. The pressure setting is convenient, accurate and stable, to ensure the stable operation of the pipe network and improve the quality of water supply.

(5) Reduced maintenance costs.

Because the frequency converter realizes soft start to the motor, the starting current is small, there is no mechanical impact on the pump unit, reducing the flow rate is also conducive to reducing the possibility of cavitation of the centrifugal pump, correspondingly extending the service life of the pump, motor and valve, greatly reducing the maintenance workload and maintenance cost.

(6) Analysis of power-saving effect:

The transformation is the production water of petrochemical water supply and drainage plant. In the production water, the power plant is a large household, and the water supply pressure is mainly to meet the demand of the power plant. The water plant generally opens two pumps to meet the water supply requirements. When replenishing the power plant, the water supply pressure should be increased to 0.56MPa, and the first water supply is about 20-30 minutes. There is no certain rule. When the water supply is not replenished, the pressure is maintained at 0.50MPa. After frequency conversion transformation, using constant pressure water supply, from figure 6, the variable frequency pump and the power frequency pump running in parallel characteristics curve, power frequency pump running curve is shown in the figure F1, point C is the single pump working point, F2 is the same pump power frequency running characteristic curve, A is the working point, head Ha = Hf, flow Qa = 2 Qf. When the flow rate changes from Qa to Qb, the resistance curve of the pipe network becomes R2, and the above correspondence is still true. At this time, the loss of the head line is Δ H=2 * (Hb-Ha) (when adjusting the valves of two pumps) or Δ H=He-Ha (when adjusting the valves of one pump). Using a variable frequency pump and a power frequency pump parallel running water supply, F3 for frequency pump running alone characteristic curve, F3, F1 under the parallel operation of working head equal principle, flow sum, two pump running curve F4, the flow Qb = Qd + Qf head Ha = Hd = Hf, from figure 6, when the greater the flow reduction.