Stability of a controlled sucker-rod pump unit drive under operating conditions and during voltage dips in the electrical network

The use of a variable frequency drive (VFD) for sucker-rod pump units (SRPUs), widely employed in oil extraction, enhances the energy and technological efficiency of oil production and reduces equipment wear. However, its application is hindered by unstable operation under insufficient balancing of the SRPU and sensitivity to short-term voltage dips, which frequently occur in the extensive electrical networks of oil fields. Insufficient balancing of the SRPU leads to the occurrence of a period within the pumping cycle where the motor operates in generator mode, caused by the unevenness and reversal of the resistance torque of the working mechanism. The motor’s transition to generator mode, as well as voltage dips in the power supply, causes the voltage in the DC link of the VFD to exceed the set limits, resulting in the drive being shut down. To investigate the processes during the operation of sucker-rod pump units and to test methods for mitigating the negative impact of generator mode and voltage dips in the power supply network on the VFD, a model of the “power grid – variable frequency SRPU drive” system with a load characteristic of this application was developed in Matlab Simulink. A series of experiments were conducted, and the results were analyzed. The suppression function of the generator mode was examined, and the feasibility of its application to real SRPUs was evaluated. The use of an uninterruptible power supply system based on battery energy storage to prevent operational interruptions during different levels of power supply voltage dips was analyzed. The resulting model can be used for general analysis of operability and stability, as well as for verifying the correct selection of key elements in the design of sucker-rod pump unit systems with variable frequency drives.