Auto-Tracking Frequency Regulation Based Energy Saving Technology for Motor Systems With Dynamic and Potential Energy Load

Abstract

Beam pumping motor system (BPMS) is a typical periodic potential energy load which is affected by factors such as down-hole load, mechanical transmission and geological structure. During a running stroke, the power fluctuates in a large range and multiple operating conditions where potential energy, electrical energy and kinetic energy are converted to one another and thus leads to lower system efficiency. For this type of load, a four-quadrant inverter is an effective method to improve the efficiency of the motor system. However, in practice, the two-quadrant variable frequency control is widely used due to its lower cost. The drawback of this control is the difficulty in realizing efficient conversion and utilization of electrical energy under the power generation mode, since the generated electrical energy is converted into thermal energy by the installed resistance brake control in the inverter, which causes additional energy consumption. To resolve this engineering problem, this paper systematically studies the influence of frequency regulation on the load torque of BPMS, an automatic tracking frequency regulation method which is suitable for the controllable conversion between the different energy forms and the fluctuation power smoothing under dynamic load conditions is proposed. This method can effectively avoid high energy consumption under power generation conditions and achieve significant energy saving effect. The correctness and practicability of the proposed method are verified by the simulations and experiments of a standard oil well. The results show that, in comparison to the traditional two-quadrant inverter, the proposed method can reduce the active power fluctuation of the system by about 20% under the premise of still using a two-quadrant inverter, and the power saving ratio is increased by more than 10%.INDEX TERMS Beam pumping motor systems (BPMSs), Dynamic and potential load condition, frequency regulation, inverter, energy saving.