System and method for driving multiple pumps electrically with a single prime mover

Abstract

A converterless motor-driven pump system includes an off-grid prime mover. The prime mover includes a rotational driveshaft that operates in response to a throttle or fuel input controller to control a rotation speed of the prime mover driveshaft. Operation of the throttle or fuel input controller is based on desired output characteristics of a pumping load. One or more electric power generators are driven by the off-grid prime mover to generate AC or DC power on an electrical bus shared by a plurality of variable speed electric motors. A plurality of pumps is connected to a common manifold shared by the plurality of pumps. The plurality of pumps is driven by the plurality of variable speed electric motors to generate a desired wellhead pressure or pumping load flow rate via the shared common manifold.

1 . A motor-driven pump system, comprising:
 a single off-grid prime mover, the single off-grid prime mover comprising a rotational driveshaft and operating in response to a throttle or fuel input controller to control a rotation speed of the prime mover driveshaft;   one or more electric power generators driven by the single off-grid prime mover rotational driveshaft to generate AC or DC power on a shared electrical bus;   a plurality of variable speed motors configured to receive electric power via the shared electrical bus; and   a plurality of pumps connected to a shared high pressure manifold and driven by the plurality of variable speed motors to generate a desired wellhead pressure via the shared high pressure manifold.   
     
     
         2 . The motor-driven pump system according to  claim 1 , wherein the throttle or fuel input controller is integrated with the motor-driven pump system. 
     
     
         3 . The motor-driven pump system according to  claim 1 , wherein the throttle or fuel input controller is remote from the motor-driven pump system. 
     
     
         4 . The motor-driven pump system according to  claim 1 , wherein the throttle or fuel input controller is a manually operated throttle or fuel input controller. 
     
     
         5 . The motor-driven pump system according to  claim 1 , wherein the throttle or fuel input controller is an automated throttle or fuel input controller. 
     
     
         6 . The motor-driven pump system according to  claim 1 , wherein the single off-grid prime mover comprises at least one of a reciprocating engine, a turbine, or a rotational energy source. 
     
     
         7 . The motor-driven pump system according to  claim 1 , wherein the one or more electric power generators comprise at least one of a permanent magnet generator, a wound-field synchronous generator, a DC generator, an induction generator, a synchronous reluctance generator, a homopolar induction alternator, or an AC generator. 
     
     
         8 . The motor-driven pump system according to  claim 7 , further comprising a generator exciter for providing excitation to the generator. 
     
     
         9 . The motor-driven pump system according to  claim 8 , further comprising a flow sensor configured to monitor a flow rate associated with the plurality of pumps and to generate a sensor signal in response thereto. 
     
     
         10 . The motor-driven pump system according to  claim 9 , wherein the throttle or fuel input controller is programmed to control the excitation of the generator exciter in response to the flow sensor signal. 
     
     
         11 . The motor-driven pump system according to  claim 1 , further comprising at least one pressure sensor configured to monitor the wellhead pressure. 
     
     
         12 . A method of operating a motor-driven pump system, the method comprising:
 controlling a driveshaft rotation speed of an off-grid prime mover in response to a throttle or fuel input controller, wherein operation of the throttle or fuel input controller is based on known characteristics of a pumping load;   controlling AC or DC power supplied to a shared electrical bus from at least one electric power generator in response to a driveshaft rotation speed of the off-grid prime mover;   controlling a speed of a plurality of variable speed motors directly in response to the AC or DC power on the electrical bus shared by the plurality of variable speed motors; and   generating a desired wellhead pressure or pumping load flow rate via a plurality of pumps driven by the plurality of variable speed motors and connected to a high pressure manifold shared by the plurality of pumps.   
     
     
         13 . The method of operating a motor-driven pump system according to  claim 12 , wherein controlling a driveshaft rotation speed of an off-grid prime mover comprises controlling a driveshaft rotation speed of at least one of a reciprocating engine, a turbine engine, or a rotational energy source. 
     
     
         14 . The method of operating a motor-driven pump system according to  claim 12 , wherein controlling the AC or DC power supplied to the shared electrical bus comprises controlling an AC power output of at least one of a wound-field synchronous generator, a permanent magnet generator, a DC generator, an induction generator, a synchronous reluctance generator, a homopolar induction alternator, or an AC generator. 
     
     
         15 . The method of operating a motor-driven pump system according to  claim 14 , wherein controlling an AC power output of the wound-field synchronous generator comprises controlling an AC power output of a wound-field exciter. 
     
     
         16 . The method of operating a motor-driven pump system according to  claim 15 , further comprising controlling the AC power output of the wound-field exciter in response to the driveshaft rotation speed of the off-grid prime mover. 
     
     
         17 . The method of operating a motor-driven pump system according to  claim 14 , further comprising controlling the AC power output of the permanent magnet generator in response to the driveshaft rotation speed of the off-grid prime mover. 
     
     
         18 . The method of operating a motor-driven pump system according to  claim 12 , further comprising linking the generated AC or DC power to the variable speed motor via a transformer. 
     
     
         19 . The method of operating a motor-driven pump system according to  claim 12 , further comprising operating the throttle or fuel input controller in response to known characteristics of a pumping load, wherein the known characteristics of the pumping load are a quadratic function of motor speed.