Electric motor control for pumpjack pumping

Abstract

A pumpjack is driven by an electric motor coupled to a gear box. A local drive controller controls the motor in accordance with a varying motor speed profile over a pumping cycle of the pumpjack. The drive controller determines, based on sensory feedback from the one or more sensors, a pumping cycle load profile, automatically determines, based on the pumping cycle load profile, a varying voltage profile, and controls the motor in accordance with the varying motor speed profile while applying the varying voltage profile to the motor.

What is claimed is: 
     
         1 . A pumpjack motor system, comprising:
 an electric motor coupled to a gear box of a pumpjack;   one or more sensors mounted to monitor at least one operating condition of the pumpjack during operation of the motor; and   a drive controller coupled to the motor and operable to control the motor in accordance with a varying motor speed profile over a pumping cycle of the pumpjack, while applying voltage to the motor;   wherein the drive controller is configured to
 determine, based on sensory feedback from the one or more sensors, a pumping cycle load profile; 
 automatically determine, based on the pumping cycle load profile, a varying voltage profile; and to 
 control the motor in accordance with the varying motor speed profile while applying the varying voltage profile to the motor. 
   
     
     
         2 . The pumpjack motor system of  claim 1 , wherein the varying motor speed profile comprises an altered version of a stroke timing curve implemented during one or more previous pumping cycles of the pumpjack. 
     
     
         3 . The pumpjack motor system of  claim 1 , wherein the varying motor speed profile comprises a plurality of target motor speeds corresponding to each of a plurality of discrete control periods within the pumping cycle of the pump jack. 
     
     
         4 . The pumpjack motor system of  claim 3 , wherein the pumping cycle load profile comprises a plurality of torque loads corresponding to each of the plurality of discrete control periods. 
     
     
         5 . The pumpjack motor system of  claim 3 , wherein the plurality of discrete control periods comprises at least 100 control periods. 
     
     
         6 . The pumpjack motor system of  claim 3 , wherein one or more of the plurality of discrete control periods of the first pump stroke cycle has a time duration of between about 5 and 100 milliseconds. 
     
     
         7 . The pumpjack motor system of  claim 1 , wherein the drive controller is configured to determine the pumping cycle load profile as a mathematical prediction based on:
 historical sensory feedback provided by the one or more sensors during one or more previous pumping cycles of the pumpjack; and/or   adjustments between the varying motor speed profile and a stroke timing curve implemented during one or more previous pumping cycles of the pumpjack.   
     
     
         8 . The pumpjack motor system of a  claim 1 , wherein at least one of the sensors comprises a load sensor. 
     
     
         9 . The pumpjack motor system of  claim 8 , wherein the load sensor is responsive to load of a polish rod of the pumpjack. 
     
     
         10 . The pumpjack motor system of  claim 1 , wherein at least one of the sensors comprises a crank rotation sensor. 
     
     
         11 . The pumpjack motor system of  claim 1 , wherein at least one of the sensors comprises a motor shaft position sensor. 
     
     
         12 . The pumpjack motor system of  claim 1 , wherein at least one of the sensors comprises a motor current sensor. 
     
     
         13 . A method of operating a pumpjack, comprising:
 operating an electric motor driving the pumpjack according to a varying motor speed profile during a first pump stroke cycle of the pumpjack, the motor speed profile comprising a plurality of target motor speeds corresponding to each of a plurality of discrete control periods;   receiving sensory feedback from one or more sensors mounted to monitor at least one operating condition of the pumpjack, the sensory feedback comprising data collected during the first pump stroke cycle;   determining a pump cycle load profile based on the sensory feedback, the pump cycle load profile corresponding to a plurality of torque loads of the electric motor at each of the discrete control periods of the first pump stroke cycle;   automatically determining, based on the pump cycle load profile, a varying voltage profile; and   operating the electric motor according to the varying motor speed profile and the varying voltage profile during a second pump stroke cycle of the pumpjack.   
     
     
         14 . The method of  claim 13 , wherein the varying motor speed profile comprises an altered version of a stroke timing curve implemented during one or more previous pumping cycles of the pumpjack. 
     
     
         15 . The method of  claim 13 , wherein the plurality of discrete control periods comprises at least 100 control periods. 
     
     
         16 . The method of  claim 13 , wherein at least one of the plurality of discrete control periods of the first pump stroke cycle has a time duration of between about 5 and 100 milliseconds. 
     
     
         17 . The method of  claim 13 , wherein determining the pump cycle load profile comprises implementing a mathematical prediction algorithm based on:
 historical sensory feedback provided by the one or more sensors during one or more previous pumping cycles of the pumpjack; and/or   adjustments between the varying motor speed profile and one or more stroke timing curves implemented during one or more previous pumping cycles of the pumpjack.   
     
     
         18 . The method of  claim 13 , wherein at least one of the sensors comprises a load sensor. 
     
     
         19 . The method of  claim 18 , wherein the load sensor is responsive to load of a polish rod of the pumpjack. 
     
     
         20 . The method of  claim 13 , wherein at least one of the sensors comprises a crank rotation sensor. 
     
     
         21 . The method of  claim 13 , wherein at least one of the sensors comprises a motor shaft position sensor. 
     
     
         22 . The method of  claim 13 , wherein at least one of the sensors comprises a motor current sensor.