Oilfield specific frequency converter suppliers remind you that frequency converters have been widely used in industrial production of enterprises and people's daily lives. The wide application of frequency converters is mainly due to their excellent energy-saving and speed regulation characteristics. China's output and energy consumption are among the highest in the world. To solve the energy consumption problem of products, in addition to other related technical issues that need improvement, variable frequency speed regulation has become an effective measure for energy conservation and improving product quality.
At present, among the pumping equipment used in most oil fields, the beam pumping unit is the most commonly used and has the largest quantity. On the one hand, the motion of the beam pumping unit is to repeatedly lift up and down, lifting once per stroke. Its power comes from two steel sliders with considerable weight driven by the electric motor. When the sliders are lifted, they act like levers, sending the oil extraction rod into the well. When the sliders are lowered, the oil extraction rod is lifted to the wellhead with oil. Due to the constant speed of the motor, the load is reduced during the descent of the sliders, and the energy generated by the motor drag cannot be attracted by the load. It will inevitably find a channel for energy consumption, causing the motor to enter a regenerative power generation state, feedback the excess energy to the power grid, and cause an increase in the main circuit bus voltage, which will inevitably have an impact on the entire power grid, leading to a decrease in power supply quality and power factor, and facing fines from power supply enterprises. Danger; Frequent high-voltage shocks can damage the motor and lack reliable protection. Once the motor is damaged, it can lead to reduced production efficiency and increased maintenance, which is extremely detrimental to energy conservation and consumption reduction of pumping equipment, causing significant economic losses to the enterprise. On the other hand, the introduction of two large steel sliders in the beam pumping unit leads to many problems such as high starting impact of the pumping unit. In addition to the two issues mentioned above, the special geographical environment of oil field production determines that oil extraction equipment has its own operating characteristics. In the early stage of oil well production, there is a large amount of oil storage and sufficient liquid supply. To improve efficiency, power frequency operation can be adopted to ensure high oil production; In the middle and later stages, due to the decrease in oil reserves, it is easy to cause insufficient liquid supply. If the motor continues to operate at power frequency, it will inevitably waste electrical energy and cause unnecessary losses. At this time, it is necessary to consider the actual working situation, appropriately reduce the motor speed, reduce the stroke, and effectively improve the filling rate. To solve the above problems, frequency conversion technology can be introduced into the control of beam pumping units.
By determining the operating frequency of the motor based on the magnitude of its working current, the stroke of the pumping unit can be conveniently adjusted according to changes in well conditions, achieving the goal of energy conservation and improving the power factor of the power grid. At the same time, the frequency converter has a low-speed soft start, and the speed can be smoothly and widely adjusted. It has complete motor protection functions, such as short circuit, overload, overvoltage, undervoltage, and stall, which can effectively protect the motor and mechanical equipment, ensure that the equipment works at a safe voltage, and have many advantages such as smooth and reliable operation, improved power factor, etc. It is an ideal solution for the transformation of oil production equipment.
At present, there are three main aspects of frequency converter transformation for beam pumping units:
(1) The frequency conversion transformation aims to improve the quality of the power grid and reduce its impact on the power grid. This is mainly concentrated in situations where power supply enterprises have high requirements for grid quality. In order to avoid a decline in grid quality, variable frequency control needs to be introduced, with the main purpose of reducing the impact of the pumping unit's working process on the grid. This application has been put on the application schedule in the Linpan oil production plant of Shengli Oilfield.
(2) Frequency conversion renovation with energy conservation as the primary goal. This is quite common. On the one hand, in order to overcome the large starting torque of oil field pumping units, electric motors are used that are much larger than the actual required power. The utilization rate of electric motors during operation is generally between 20% and 30%, with the highest not exceeding 50%. Electric motors are often in a light load state, resulting in waste of motor resources. On the other hand, the working condition of the pumping unit is continuously changing, which depends on the underground state. If it is always operating at power frequency, it will inevitably cause waste of electrical energy. In order to save energy and improve the efficiency of electric motors, frequency conversion transformation is needed.
(3) Frequency conversion renovation aimed at improving the quality of the power grid and energy conservation. This situation combines the advantages of the above two transformations and is an important development direction in applications.
In the actual application process, many problems have arisen, mainly focusing on the processing of energy generated by the power generation state of the beam pumping unit. For the first scenario, using a regular frequency converter with an energy consuming braking unit can be relatively convenient, but this comes at the cost of consuming more energy, mainly because the generated energy cannot be fed back to the grid. When the frequency converter is not used and the motor is in an electric state, the motor absorbs electrical energy from the grid (the meter rotates forward); When the electric motor is in the generating state, it releases energy (the meter reverses), and the electrical energy is directly fed back to the grid without being consumed by local equipment. The overall performance is that the power factor of the power supply system of the pumping unit is relatively low, which has a significant impact on the quality of the power grid. But when using a regular frequency converter, the situation has changed. The input of a regular frequency converter is diode rectified, and energy cannot flow in the opposite direction. The above part of the electrical energy does not have a path back to the grid and must be consumed locally using resistors, which is why energy consuming braking units must be used. For the second and third scenarios, it is necessary to properly handle the electrical energy generated by the motor's power generation status and feedback it to the grid. Otherwise, the energy saved by adjusting the stroke of the pumping unit may not be able to offset the energy consumed by the frequency converter braking unit, resulting in energy consumption during frequency conversion operation, which goes against the goal of energy conservation. In order to solve this problem, it is necessary to modify the ordinary frequency converter by introducing a dual PWM structure in the structure to ensure that the electricity generated during power generation is fed back to the grid; Introducing adaptive control in control methods to adapt to the changing working environment of beam pumping units.