Abstract: A method and apparatus are provided for estimating and/or precluding stick-slip, or other oscillatory or resonant behavior, through use of a virtual transducer, which precludes the need for having sensors located adjacent to a driven element of the system, or adjacent contact surfaces at which the stick-slip relative motion may occur. Parameters measurable at a drive mechanism are utilized for controlling a system in a manner which precludes stick-slip, or other oscillatory or resonant behavior, of the driven element. Relative motion between contacting surfaces in the driven element, prone to stick-slip behavior, is controlled such that, after sufficient force is applied by the drive element to overcome static friction forces between the contacting surfaces and break them free from one another, relative motion between the surfaces is maintained at a high enough relative speed that the surfaces are precluded from statically contacting one another, so that stick-slip behavior is precluded.

Abstract: A rod pump control system includes a parameter estimator that determines from motor data parameters relating to operation of the rod pump and/or downhole dynamometer card without the need for external instrumentation, such as down hole sensors, echo meters, flow sensors, etc. In one embodiment, instantaneous motor current and voltage together with pump parameters are used in determining rod position and load. The rod position and load are used to control the operation of the rod pump to optimize the operation of the pump. Also disclosed in a pump stroke amplifier that is capable of increasing pump stroke without changing the overall pumping speed, or in the alternative, maintaining the well output with decreased overall pumping speed.

Abstract: A system for controlling operation of a progressing cavity pump to maintain the motor operating under power disturbance conditions. For a blackout condition, a backspin controller uses regenerative power to provide controlled deceleration of the pump, counteracting backspin and preventing backspinning freely. For a brownout condition, a power dip controller weakens the motor field to maximize pump production consistent with reduced input power availability. For a phase loss or voltage imbalance condition, a phase loss controller reduces motor power output to keep drive system output power at or below single phase capacity.