In the core of the control program is the backspin control. When PCP or ESP is stopped, and fluid flows back to the well, this function controls the reverse rotation of the rotor.
In the case of PCP pump the rod connecting the motor to the pump has rotational tension while it is operating, when the motor is stopped this tension will unwind rapidly. This rapid release of energy must be controlled to avoid damage to the rod.
With ESP there is no risk of damaging the equipment, but the reverse rotation must be identified to prevent starting of the motor.