Rapid Soft Re-switching Strategy of Intermittent Supply for Energy Saving in Beam Pumping Motors Systems With Dynamic Load Conditions

Intermittent supply technology is suitable for beam pumping motor systems (BPMSs), as the supply is cut off when the motor operates in generator mode, and the losses of motor and transmission line can be eliminated effectively. However, the supply is required to be rapidly re-switched on after power-off control, without large inrush current. Comparing to the conventional soft starting, the dynamic load torque and the varying motor speed should be considered particularly. To solve this problem, a rapid soft re-switching control strategy is proposed with the dynamic load considered. First, the optimal re-switching time is determined; the method of firing angle determination and the related control strategy are then proposed under the preconditions of reasonable inrush current at the initial stage of re-switch process, as well as, meeting the demand of load torque. With the proposed control strategy, the electromagnetic torque can match the load-torque requirement with limited inrush current during the re-switching process. An energy-saving device is developed and the experimental validation is performed on a 37-kW beam pumping motor in an oil field.