Ťažobný priemysel

Application of SLANVERT Inverter in Water Injection Pump of Liaohe Oil Field

Application solution: original system is started by soft starter, and operation pressure of water injection pump can not be adjusted. In addition, in the open air, capacity of transformer of the equipment for power supply is limited and voltage is unstable; sometimes the soft starter is unable to be started due to trip or damage of transformer caused by overload of the current. If the inverter is used, water injection with constant pressure can be achieved and it is free of start striking current and with sound protection function to ensure safe and reliable operation of the equipment effectively. With consideration of control reliability, frequency conversion cabinet is equipped with conversion circuit of power frequency / variable frequency. In order to prevent damage of water injection pump under the condition of dry run, install the electro connecting pressure gauge at the entry of water pump to detect the pressure and conduct water shortage detection; in case of water shortage, it will send alarm and stop running. In order to prevent damage of pressure transmitter to make overload of pressure caused by 50Hz operation of frequency conversion, electro connecting pressure gauge is installed at water outlet to detect pressure at the water outlet.

Points must be paid attention to in frequency conversion commissioning: water injection pump is controlled by constant pressure. As pump pressure is high (20kPa), it is required that the pressure shall not be over-high and the proportional element shall not be too large, pressure must be ensured to increase in a stable way. PID parameters are set as below:

F814=10, F815=5, F816=0.1

Characteristics for start of water injection pump: current is high at starting point, and current is low after starting. For example, the 280kW water injection pump is this case, its current is 220A when the power reaches 50Hz.


Application of SLANVERT SB70G Inverter in Oil-gas Transfer Pump of Oil Field

I. Preface
We apply SLANVERT SB70G Inverter on 30kW CSY11-2 oil-gas transfer single-screw pump to conduct speed regulation control, and install quality-reliable variable frequency speed control device so as to solve the realistic problems arising out of production. Site use effect is quite good and prominent economic and social benefits are achieved.

II Control Solutions
Method of closed-loop control together with open-loop control is applied in control solutions of variable frequency speed regulation technology for oil-gas transfer pump unit. Closed-loop control and open-loop control method are shown in Fig. 1 and Fig. 2 respectively to meet the requirements of site production.

Fig. 1 Schematic Diagram of Variable Frequency Closed-loop Control

Fig. 2 Schematic Diagram of Variable Frequency Open-loop Control

2.1 Technical Solution on Application of Closed-loop Control
Install the ball float type level meter with output of 4-20mA analog signal on the oil tank to transmit the level signal to inverter. Inverter compares the signal received from level meter with the set value of inverter and then adopts PID regulation and control calculation method to regulate and control level of oil tank automatically through variation of output frequency of inverter to reach the objectives of energy saving, consumption reduction and smooth production and automatic control of oil well.
2.2 Technical Solution on Application of Open-loop Control
Level meter is not installed on the oil tank; level detection is conducted by manual regular detection. Operator regulates the output frequency of inverter and controls output of oil-gas transfer pump through manual regulation of 5kΩ potentiometer according to detected level of oil tank so as to con troll level of oil tank and reach the objectives of energy saving, consumption reduction and smooth production of oil well.
After inverter is installed on the oil-gas transfer pump, working current and input power of the motor is reduced obviously with evident effect of power saving, and power factor is increase accordingly and system efficiency is also increased obviously with evident effect of power saving.


Frequency-Conversion Speed Regulation of Electrical Submersible Pump

I General
An electrical submersible pump is a multistage centrifugal pump for oil well downhole work, and one of the commonly used oil production equipments. The pump can work in 2~3km deep downhole with high-temperature and high-corrosion environment continuously for a long period. As it goes deep into the oil reservoirs, the work efficiency is high, and it is more widely applied in oil fields. The motors of the electrical submersible pumps have powers that are not large, generally ranging 55~75kW, and have voltage grade of 1140V.
After the supply voltage rises to 1140V, the voltage drop of the line meets the requirements for motor to start and run, but the impulse current is large in energized starting, and the distributed inductance causes the excessively high counter-voltage in the system, often leading damage of motor, and insulations of the line. As the geological condition change of the oil well is large, and the design margin of the electric submersible pump is often too large; especially when the downhole liquid is insufficient, the oil pressure produce by the pump is too high, leading to shortened pump life, increased capability of repair and replacement. In addition, when the submersible pump is downhole 2 ~ 3km from the ground, local power factor compensation cannot be implemented, and the reactive power consumed by motor should be supplied by the power supply. The line both active current and reactive current transmission, and the resultant current will be very large, and the loss will be also large. To solve the above problem, frequency-conversion speed regulation must be performed for the pump motor.

II Advantages of Frequency-Conversion Speed Regulation for Electrical Submersible Pump
The inverter has soft starting function, and can be successfully started under the rated current of motor, so the back EMF and impulse current are very small and the capability of the problem that the insulation is liable to damage is low. With frequency converter, regardless of heavy or light load, the system will have high power factor, and the quadergy needed by the motor is directly obtained from the converter, which can reduce the energy loss of the supply line. In addition, the oil output can be regulated according to the current condition of the oil well to make the well work in the best condition with reduced failure rate and increased efficiency. Pressure, temperature closed-loop system can also be formed to enhance the automation and realize optimal control.
After adoption of frequency-conversion speed regulation, for rich oil wells, increased production may be realized; for poor oil wells, continuous production with reduced well shut-down times can be made and energy saving purpose can be achieved; for sand-containing wells, the pump seizure can be reduced with reversed sand dumping to extend pump life; for gas-containing wells, speed can be increased and the air lock caused by poor oil-gas separation can be reduced to increase production efficiency; for wax-containing wells, waxing and scaling can be reduced to reduce the pipeline blockage; for heavy oil wells, low-speed and large-power operation can be made with reduced well shut-down times to obtain considerable energy saving effects.

III Technical Solution of Frequency-Conversion Speed Regulation
SLANVERT 1140V MV inverter is adopted. To reduce the output harmonics of the inverter, output reactor and output filter or sine filter are required to be installed at the output end of the inverter. The mode of operation is manual control. The operator can manually adjust the output frequency of the inverter according to site conditions to meet the technological needs.
Our company is developing 1140V three-level inverter. Compared with the two-level one, three-level inverter has output voltage waveform composed of trapezoidal pulse, but with half pulse amplitude, and well solve the problems in insulation and harmonics caused by high dv/dt, so that the output waveform of the inverter is more like the sinusoidal wave. It thoroughly solves the problems such as the insulation deterioration caused by the impact of current inversion of parts to insulation of the motor, the corrosion of the shaft voltage to bearing of the motor, commission interference and radiation interference, and reduces the leakage current and motor noise. After successful R&D, 1140V three-level inverters are adopted for frequency-conversion speed regulation of all electrical submersible pumps.


Frequency-Conversion Speed Regulation of Oil Pumping Unit

I Frequency-Conversion Speed Regulation of Oil Pumping Unit
Frequency-conversion speed regulation for walking beam pumping unit motor may remove the impact during the process of starting. Regenerated energy is generally dealt with by dynamic braking of resistor. If the power supply is stable and of good quality, regenerative braking may also be used.
At present, there are two main aspects in transformation of the technology of frequency-conversion speed regulation for walking beam pumping units:
(1) Frequency-conversion energy-saving transformation.
(2) Change of upward and downward running speed of oil rod can improve productivity in some circumstances.

II Modification Cases
Since 2002, Senlan Shenyang Branch has made transformation to hundreds of oil pumping units of Dagang Oil Field. The pumping units have power of generally 30kW~75kW, and mostly 37kW and 45kW. In selecting inverters, considering that the pumping units have relatively large moment of inertia, general invertors for V/F regulation should be one gear larger, and vector control inverter of good starting torque would be better, such as SB61 +, SB70G, provided that the inverter has rated current greater than or equal to the rated current of motor.
In addition, as regenerated energy may be produced during operation of the pumping units, each converter should be equipped with the appropriate braking unit and braking resistor, so that the energy can be consumed by resistance. To use this part of the regenerated energy, DC bus can be adopted at the place (platform) where several pumping units are concentrated.