Regenerated Power Accumulator for Rod Lift Drive

Abstract

A variable speed drive for use in connection with a beam pumping unit has a pair of DC bus rails that include a positive DC bus rail and a negative DC bus rail. The variable speed drive further comprises a rectifier section, an inverter section connected between the DC bus rails and a primary capacitor bank. The primary capacitor bank includes a primary capacitor and an overvoltage switch. The variable speed drive further includes an auxiliary capacitor bank that has an auxiliary capacitor, a charge diode connected between the auxiliary capacitor and the overvoltage switch, and a discharge diode connected between the auxiliary capacitor and the positive DC bus rail.

What is claimed is: 
     
         1 . A variable speed drive for use in connection with a beam pumping unit, the variable speed drive comprising:
 a pair of DC bus rails, wherein the pair of DC bus rails comprise a positive DC bus rail and a negative DC bus rail;   a rectifier section connected between the DC bus rails;   an inverter section connected between the DC bus rails;   a primary capacitor bank connected between the DC bus rails, wherein the primary capacitor bank comprises:
 a primary capacitor; and 
 an overvoltage switch; and 
   an auxiliary capacitor bank, wherein the auxiliary capacitor bank comprises:
 an auxiliary capacitor; 
 a charge diode connected between the auxiliary capacitor and the overvoltage switch; and 
 a discharge diode connected between the auxiliary capacitor and the positive DC bus rail. 
   
     
     
         2 . The variable speed drive of  claim 1 , wherein the overvoltage switch is selected from the group consisting of insulated-gate bipolar transistors, semiconductor switches and mechanical switches. 
     
     
         3 . The variable speed drive of  claim 2 , wherein the overvoltage switch is an insulated-gate bipolar transistor. 
     
     
         4 . The variable speed drive of  claim 2 , wherein the auxiliary capacitor bank further comprises a resistor between the charge diode and the auxiliary capacitor. 
     
     
         5 . A motor drive assembly for controlling the operation of a plurality of beam pumping units, the motor drive assembly comprising:
 a central auxiliary capacitor bank; and   a plurality of variable speed drives, wherein each of the plurality of variable speed drives is connected between the central auxiliary capacitor bank and a corresponding one of the plurality of beam pumping units.   
     
     
         6 . The motor drive assembly of  claim 5 , wherein each of the plurality of variable speed drives is connected to the central auxiliary capacitor bank through an overvoltage switch that permits the central auxiliary capacitor bank to be automatically charged by the corresponding variable speed drive. 
     
     
         7 . The motor drive assembly of  claim 6 , wherein each of the overvoltage switches is selected from the group consisting of insulated-gate bipolar transistors, semiconductor switches and mechanical switches. 
     
     
         8 . The motor drive assembly of  claim 7 , wherein each of the overvoltage switches is an insulated-gate bipolar transistor. 
     
     
         9 . The motor drive assembly of  claim 5 , wherein each of the plurality of variable speed drives comprises:
 a pair of DC bus rails, wherein the pair of DC bus rails comprise a positive DC bus rail and a negative DC bus rail;   a rectifier section connected between the DC bus rails;   an inverter section connected between the DC bus rails; and   a primary capacitor bank connected between the DC bus rails, wherein the primary capacitor bank comprises a primary capacitor.   
     
     
         10 . The motor drive assembly of  claim 5 , wherein the central auxiliary capacitor bank comprises:
 an auxiliary capacitor;   a charge diode connected between the auxiliary capacitor and the overvoltage switches of each of the plurality of variable speed drives; and   a discharge diode connected between the auxiliary capacitor and the positive DC bus rails of each of the plurality of variable speed drives.   
     
     
         11 . The motor drive assembly of  claim 10 , wherein the auxiliary capacitor bank further comprises a resistor between the charge diode and the auxiliary capacitor. 
     
     
         12 . An energy efficient drive system for a beam pumping unit, the energy efficient drive system comprising:
 a variable speed drive,   an external switch connected to the DC bus rails of the variable speed drive; and   an auxiliary capacitor bank.   
     
     
         13 . The energy efficient drive system of  claim 12 , wherein the variable speed drive comprises:
 a pair of DC bus rails, wherein the pair of DC bus rails comprise a positive DC bus rail and a negative DC bus rail;   a rectifier section connected between the DC bus rails; and   an inverter section connected between the DC bus rails.   
     
     
         14 . The energy efficient drive system of  claim 13 , wherein the variable speed drive further comprises a primary capacitor bank connected between the DC bus rails. 
     
     
         15 . The energy efficient drive system of  claim 14 , wherein the primary capacitor bank further comprises an overvoltage switch. 
     
     
         16 . The energy efficient drive system of  claim 15 , wherein the overvoltage switch is selected from the group consisting of insulated-gate bipolar transistors, semiconductor switches and mechanical switches. 
     
     
         17 . The energy efficient drive system of  claim 16 , wherein the overvoltage switches is an insulated-gate bipolar transistor. 
     
     
         18 . The energy efficient drive system of  claim 12 , wherein the auxiliary capacitor bank comprises:
 an auxiliary capacitor;   a charge diode connected between the auxiliary capacitor and the external switch; and   a discharge diode connected between the auxiliary capacitor and the positive DC bus rail.   
     
     
         19 . The energy efficient drive system of  claim 18 , wherein the auxiliary capacitor bank further comprises a resistor between the charge diode and the auxiliary capacitor.