Fluid extraction system and related method of controlling operating speeds of electric machines thereof
View Patent ↗A fluid extraction system is presented. The fluid extraction system includes a direct current (DC) bus and a plurality of fluid extraction sub-systems configured to be electrically coupled to the DC-bus. At least one fluid extraction sub-system includes an electric machine configured to aid in the extraction of a fluid from a well. The electric machine includes a plurality of phase windings and a rotor. The at least one fluid extraction sub-system further includes a control sub-system to control a rotational speed of the rotor by selectively controlling a supply of a phase current to the plurality of phase windings such that the rotational speed of the rotor of the electric machine is different from rotational speed of a rotor of another electric machine in at least one of other fluid extraction sub-systems. Related method for controlling rotational speeds of electric machines is also presented.
1. A method for controlling operating speeds of electric machines in a plurality of fluid-extraction sub-systems coupled to a direct current (DC) bus for receiving a DC voltage, the method comprising:
determining a desired operating speed of an electric machine of each of the plurality of fluid-extraction sub-systems;
determining a maximum operating speed of the determined desired operating speeds;
adjusting a magnitude of the DC voltage on the DC-bus based on the maximum operating speed such that at least one electric machine of the electric machines is operable at the maximum operating speed;
generating a speed control signal based on the desired operating speed of each electric machine and a desired magnitude of a phase-shift corresponding to the desired operating speed of each of the electric machine of each of the plurality of fluid-extraction sub-systems; and
communicating the speed control signal to the plurality of fluid-extraction sub-systems such that the electric machine of each of the plurality of fluid-extraction sub-systems are operated at the corresponding desired operating speed.
2. The method of claim 1 , wherein the operating speed is indicative of a rotational speed of a rotor in the electric machine.
3. The method of claim 1 , wherein the desired operating speed of the electric machine is determined based on a desired flow-rate of a fluid to be extracted by the corresponding fluid-extraction sub-system of the plurality of fluid-extraction sub-systems.
4. The method of claim 1 , wherein the magnitude of the DC voltage is determined based on a relationship between the operating speed and the DC voltage on the DC-bus.
5. The method of claim 1 , wherein generating the speed control signal comprises determining a phase-shift corresponding to the desired operating speed of the electric machine for each of the plurality of fluid-extraction sub-systems.
6. The method of claim 5 , wherein generating the speed control signal further comprises generating a speed level sub-code for each the phase-shift corresponding to the desired operating speed of the electric machine for each of the plurality of fluid-extraction sub-systems.