Rapid Soft Re-Switching Strategy of Intermittent Supply for Energy Saving in Beam Pumping Motor System with Dynamic Load Condition

Abstract

Intermittent supply technology is suitable for Beam Pumping Motor Systems (BPMSs). As the supply is cut off when the motor operates in generator mode, 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 incurring large inrush current. In comparison 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 conditions considered. Firstly, the optimal re-switching time is determined according to the characteristics of inrush current with the different speed; the method of firing angle selection and the related control strategy for supply re-switching are proposed under the preconditions of reasonable inrush current at the initial moment, as well as, meeting the load when switching to fully sinusoidal supply. 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 controller is developed and the experimental validation is performed on a 37-kW beam pumping motor in an oil field. The correctness and effectiveness of the proposed strategy are verified.