Abstract: This paper analyzes the control requirements of traditional beam pumps and proposes a control scheme using Vacon frequency converters. The Vacon frequency converter utilizes the Vacon NC1131-3 Engineering programming tool to modify the standard application macro into a special application macro for beam pumps, "Beam Pumper," achieving the goal of increasing production and saving energy. Keywords: Vacon frequency converter; beam pump; beam pumper application macro; NC1131-3 I. Energy-Saving Principle of Using Variable Frequency Drive for Beam Pumps First, it is necessary to clarify the load characteristics of the beam pump: constant speed operation; due to the counterweight, it is a variable torque and variable power load. Currently, the traditional pumping unit systems commonly used in domestic oilfields have the following characteristics: long operating time, underpowered operation, low efficiency, high energy consumption, and inconvenient stroke and stroke rate adjustment. Therefore, it is necessary to use frequency converters (VDCs) in pumping units to achieve energy saving and increased production. Any well-balanced pumping unit has a power generation state. However, if the VDC operates at a constant speed and maintains the same pumping frequency as the mains frequency (i.e., the VDC continuously outputs a 50Hz mains frequency and maintains two power generation states in one stroke), it will cause the VDC to experience overvoltage faults due to increased DC bridge voltage. Clearly, this is not feasible. If the VDC is allowed to operate at variable speed while maintaining the original pumping frequency, the output frequency of the VDC increases during power generation, keeping the DC bridge voltage within a certain range, thus preventing overvoltage. To maintain a constant number of pumping cycles, the inverter's operating speed will decrease in motor mode, meaning its output frequency will decrease. With constant torque, the energy absorbed from the grid will also decrease. In generator mode, the inverter no longer needs to absorb energy from the grid, and some energy is stored in its DC capacitor. This energy will be used for power supply in motor mode, thus further reducing the energy absorbed by the pumping unit from the grid. II. Challenges of Variable Frequency Drive Retrofitting Traditional Pumping Units With the increasing demands for pumping unit output and energy conservation in crude oil production, numerous experiments have been conducted domestically on variable frequency energy-saving retrofitting of pumping units, but none have been very successful. The main reasons are: 1. A beam pumping unit operates in generator mode twice in one working cycle. If no effective measures are taken during this time, it will cause overvoltage faults in the inverter. Traditional solutions include using a four-quadrant inverter with feedback, or using a regular inverter with energy-saving braking or frequency reduction, or connecting a large-capacity energy storage capacitor in parallel with the DC bridge. Using a four-quadrant frequency converter with feedback will increase the system cost and prolong the time for the oilfield to recover its costs. When using a regular frequency converter with energy-saving braking, different oil wells will require different braking resistors, and the size of the braking resistor will also change with the oil layer. Otherwise, overvoltage faults will still occur, which will greatly reduce the energy-saving effect. When using a regular frequency converter at reduced frequency, it is difficult to improve the efficiency of oil pumping. When a large capacitor is connected in parallel to the DC bridge of the frequency converter, the capacity of the parallel capacitor also needs to be changed with the oil layer. Otherwise, overvoltage will still occur. 2. The starting of a beam pumping unit requires a large starting torque. If the parameters of the frequency converter are not set properly, it will cause overcurrent or failure to start. 3. Previous design schemes rarely considered changes in oil level and oil concentration in oil wells, and did not have a significant effect on improving production. III. VACON Pumping Unit Dedicated Frequency Conversion Energy-Saving Drive Solution The VACON pumping unit dedicated frequency conversion energy-saving drive solution is mainly based on the Beam Pump application macro software package of VACON frequency converters. This application macro, modified from the standard VACON application macro, is a new type of intelligent electrical oilfield pumping unit control method specifically developed based on actual oilfield conditions and the mechanical structure of beam pumping units. It can autonomously determine the upstroke and downstroke of the pumping unit and adjust the speed of these strokes in real time according to the actual conditions of the oil well. Therefore, during actual pumping, it increases the amount of oil produced per pumping stroke without changing the number of pumping strokes per minute, thus improving the pumping unit's output. The Vacon frequency conversion energy-saving solution ensures a constant pumping time (SPM) by adjusting the frequency reference value inside the frequency converter. All reference commands are converted into pumping strokes per minute. The control principle is: providing appropriate current limits for normal operation; in motor mode, the actual motor speed is lower than the reference value; in generator mode, the motor speed is allowed to be higher than the reference value, thereby maintaining a constant average pumping time. When using balanced load applications, two different reference frequency values ​​are used for the upstroke and downstroke. The advantages of this scheme are: 1. High efficiency and energy saving: The controller has no braking resistors. When the pumping unit is in generator operation, the frequency converter automatically increases the motor speed and stores the energy generated during generator operation, reducing unnecessary energy loss compared to traditional designs. 2. Safe operation and reliable performance: The drive control does not require any PLC; it is based on the frequency converter's dedicated control program and has both power frequency and variable frequency operation modes. These two operation modes are interlocked and independent. The frequency converter has a wide input voltage range, making the system safer and more reliable. 3. User-friendly interface, easy installation, and simple operation: The frequency converter's display panel can directly display the output voltage, output current, output frequency, energy consumed by the motor, running time, number of pumping operations, etc. The frequency converter's operating reference value can be directly set to determine the number of pumping operations, thus improving upon the traditional operation method of controlling the pumping unit by setting the motor's operating frequency. The above scheme is applicable to the three common types of traditional pumping units: beam-balanced, crank-balanced, and compound-balanced. In practical applications, after inputting the necessary pumping unit parameters, the controller will perform static modeling of the pumping unit and modify the mathematical model of the pumping unit in real time according to the actual operating conditions of the pumping unit to achieve the goal of increasing production and saving energy. IV. Application Cases The VACON pumping unit-specific variable frequency energy-saving drive solution based on Beam Pumper application macros has been widely deployed in Liaohe Oilfield, Xinjiang Oilfield, Daqing Oilfield, and Shengli Oilfield. Here, we only take the Wa 3737 well and Hai C9-17 well in Liaohe Oilfield as examples, and their application diagrams are shown in the figure below. To ensure that production is not delayed in the event of a frequency converter failure, a power frequency bypass can be added. When the frequency converter is running, C3 is interlocked with C1 and C2, preventing simultaneous closing. That is, under normal operating conditions, switches C1 and C2 are both closed, and C3 is open; when the frequency converter fails, C1 and C2 are open, and C3 is closed. The following table shows the actual application results: [align=center] Table 1: Comparison of Vacon Variable Frequency Energy Saving Solution Effects in Liaohe Oilfield[/align] The system design indicators are a power saving rate of 15% and a production increase rate of 5%. As shown in the table above, the Vacon variable frequency energy saving solution has met the design requirements, and the energy saving effect is significant. V. Conclusion The continuous rise in energy prices and the increasingly stringent energy-saving requirements of national energy laws are important issues that all industries, including oil drilling, must consider when designing drive systems. In addition, with the continuous increase in the oil production industry's requirements for oil output and system operating costs, the application of variable frequency drive solutions will inevitably become more widespread. Practice has proven that the VACON pumping unit-specific variable frequency energy-saving drive solution introduced in this article has demonstrated significant energy-saving and production-increasing effects in application, and is an ideal choice to replace traditional pumping unit drive solutions. References: 1. Zhang Jianjun et al., Design and Calculation of Beam Pumping Units, Petroleum Industry Press, 2005. 2. VACON Plc, VACON NX Inverter User Manual, 2006. 3. VACON Plc, VACON NX “ALL IN ONE” Application Manual, 2006. 4. VACON Plc, VACON NC1131-3 Programming and Engineering Design Manual, 2006.