A Method for Efficiently Controlling the Sucker-Rod Pump Electric Drive
The results from elaborating a new method for controlling the sucker-rod pump (SRP) frequency-regulated electric drive equipped with an induction motor are presented. The aim of the study is to achieve better energy efficiency of the SRP electric drive operation due to a smaller amount of electricity consumed in the working cycle. Smaller energy consumption is achieved by using the kinetic energy of the pump’s unbalanced mechanical parts which make reciprocating movement in a vertical plane. To implement this principle in the pump electric drive operating as a frequency converter -induction motor system, it is proposed to use a periodically varying motor shaft rotation frequency reference signal instead of a constant signal. The efficiency of such solution is analytically substantiated by taking into account the balance of kinetic and potential energy in the SRP bar working movement cycle. Mathematical expressions proceeding from which the required speed reference signal ensuring smaller electricity consumption by the pump electric drive should be produced are given. One possible circuit solution using which the expected effect can be obtained implies the use of a dedicated computing device (controller) connected to the pump electric drive frequency converter’s control input. This device will perform the function of a dedicated adjuster for the pump rod and piston motion speeds. The device should be supplemented with a position sensor installed on the SRP crankshaft, which will transmit the pump rod motion direction signal to the speed adjusting controller. When the pump rod moves downward, the speed reference signal will smoothly increase, thus resulting in a growth of stored kinetic energy, and when the rod moves upward, the speed reference signal will smoothly decrease, due to which the stored kinetic energy will be usefully consumed. Thus, in using the proposed control method, it becomes possible to decrease the flow of energy passing through the motor and frequency converter with the pump mechanical work remaining unchanged. It is exactly owing to this circumstance that better energy efficiency of the process installation is obtained.