Electric machine driving method and system under non-conventional work mode of oil pumping unit

An electric machine driving method under a non-conventional work mode of an oil pumping unit, comprising:

• switching a crank complete-cycle operation to a crank incomplete-cycle pumping operation, and then to a crank incomplete-cycle no-pumping operation without shutting down the oil pumping unit;
• or switching the crank incomplete-cycle no-pumping operation to the crank incomplete-cycle pumping operation, and then to the crank complete-cycle operation without shutting down the oil pumping unit, wherein, the crank complete-cycle operation uses a utility frequency driving mode, the crank incomplete-cycle pumping operation and the crank incomplete-cycle no-pumping operation use a variable frequency driving mode;
• driving the oil pumping unit, by the variable frequency driving mode, to perform the crank incomplete-cycle pumping operation and the crank incomplete-cycle no-pumping operation;
• adjusting and controlling mechanical energy accumulated by the oil pumping unit by means of adjusting a swing amplitude of a crank during the crank incomplete-cycle pumping operation and the crank incomplete-cycle no-pumping operation, wherein a peak rotating speed of the electric machine in a bidirectional motion is constantly adjusted;
• and switching from the variable frequency driving mode to the utility frequency driving mode when the peak rotating speed of the electric machine in a direction of the bidirectional motion under the utility frequency driving mode falls within a range containing a rated rotating speed under the utility frequency driving mode of the electric machine;
• and
• turning off the utility frequency driving mode to make the oil pumping unit enter a free-running operation state;
• and switching to the variable frequency driving mode, when the peak rotating speed of the electric machine falling within a range containing a predetermined rotating speed of the electric machine.