Abstract: An electric submersible pump (ESP) variable speed drive (VSD) controller is described. A VSD control system includes a pump assembly including an induction motor operatively coupled to a pump, a power cable and a transformer electrically coupled between the induction motor and a VSD controller that controls a speed of the induction motor, the VSD controller including a converter section that sends a direct current (DC), a DC link including a DC smoothing capacitor that smooths the DC, an inverter that converts the smoothed DC to a pulse width modulated (PWM) output voltage, the inverter including at least one silicon carbide (SiC) power semiconductor module, and a PWM filter that filters the PWM output voltage to produce near sinusoidal voltages, the PWM filter including inductors, and the PWM filter sending voltage to the transformer.

Abstract: An electric submersible pump (ESP) variable speed drive (VSD) controller is described. A VSD control system includes a pump assembly including an induction motor operatively coupled to a pump, a power cable and a transformer electrically coupled between the induction motor and a VSD controller that controls a speed of the induction motor, the VSD controller including a converter section that sends a direct current (DC), a DC link including a DC smoothing capacitor that smooths the DC, an inverter that converts the smoothed DC to a pulse width modulated (PWM) output voltage, the inverter including at least one silicon carbide (SiC) power semiconductor module, and a PWM filter that filters the PWM output voltage to produce near sinusoidal voltages, the PWM filter including inductors, and the PWM filter sending voltage to the transformer.

Abstract: An electric submersible pump (ESP) variable speed drive (VSD) controller is described. A VSD control system includes a pump assembly including an induction motor operatively coupled to a pump, a power cable and a transformer electrically coupled between the induction motor and a VSD controller that controls a speed of the induction motor, the VSD controller including a converter section that sends a direct current (DC), a DC link including a DC smoothing capacitor that smooths the DC, an inverter that converts the smoothed DC to a pulse width modulated (PWM) output voltage, the inverter including at least one silicon carbide (SiC) power semiconductor module, and a PWM filter that filters the PWM output voltage to produce near sinusoidal voltages, the PWM filter including inductors, and the PWM filter sending voltage to the transformer.

Abstract: An electrical submersible pumping (ESP) system can include a pump located in a wellbore, a motor attached to the pump, a power source located at the surface, a cable electrically coupling the power source and the motor, and a current sensor. The ESP system can also include a controller communicating with the current sensor to calculate a voltage drop associated with the cable responsive to an impedance of the cable. The controller can also control a power source output voltage responsive to the calculated voltage drop. For example, the controller can adjust the power source output voltage to minimize a cable current while maintaining a minimum motor voltage. The controller can also control a motor shaft speed by changing a power source output voltage frequency to compensate for changing slip and adjust the power source output voltage to minimize the cable current while maintaining a minimum motor voltage.

Abstract: A device and method can detect, and also break, an occurrence of gas lock in an electrical submersible pump assembly in a well bore based upon surface or downhole data without the need for operator intervention. To detect an occurrence of gas lock, an instantaneous value is monitored using a sensor. Then a controller compares the instantaneous value to a threshold value over a predetermined duration to thereby detect the occurrence of gas lock in the electrical submersible pump assembly. Sensors can include, for example, a differential pressure gauge, a pressure gage located in a pump stage located toward the inlet, a fluid temperature sensor located toward the discharge, a free gas detector located near the pump discharge, an electrical resistivity gage, a flow meter located within surface production tubing, and a vibration sensor attached to a tubing string to measure a vibration signature.

Abstract: Systems and methods for using variable speed drives to restart downhole submersible pump motors. In one embodiment, a downhole pump is controlled using a variable speed drive that includes a control system configured to detect interruptions in the operation of the pump system. After an interruption that requires the restart of the pump motor, the control system determines the reverse rotational speed of the pump motor and restarts the motor when this speed is sufficiently low. The control system may be configured to reduce the output voltage of the variable speed drive and sweep through a range of output frequencies to determine the frequency at which the current drawn by the motor is lowest. This is the frequency at which the drive's output matches the speed of the motor and the apparent impedance of the motor is highest. When the speed is low enough, the motor is restarted.

Abstract: Systems and methods for reducing harmonic distortion in a power system resulting from non-linear loading on the power system. The power at an interface with a power source is measured, and then distortion in the waveforms of the supplied power is identified. Cancellation signals which cancel all or part of the distortion are then generated and injected at the interface. In one embodiment, the power is sampled to determine the waveform, and then a Fast Fourier Transform is performed on the waveform to convert it to the frequency domain. Harmonics of the fundamental frequency can then be identified, and conjugates of the harmonics generated. An inverse Fast Fourier Transform is performed on the conjugates to generate a signal which is amplified to produce the cancellation signal.

Abstract: Systems and methods for providing ride-through for interruptions in the power supplied to drives that are used to control equipment such as downhole submersible pumps. In one embodiment, a variable speed drive includes converter and inverter sections, a capacitor bank and a control system. The drive shuts down the converter section upon detecting a disruption in the AC input power and continues to generate output power by drawing on the energy stored in the capacitor bank. When the AC input power returns (or begins to return) to normal, the drive resumes operation of the converter section in a controlled manner (e.g., by presetting the firing angle of the SCR's in the converter to match the voltage across the capacitor bank.) The drive thereby limits the current that recharges the capacitor bank and prevents sudden inrushes of current that could damage the drive.

Abstract: An electrical submersible pumping (ESP) system can include a pump located in a wellbore, a motor attached to the pump, a power source located at the surface, a cable electrically coupling the power source and the motor, and a current sensor. The ESP system can also include a controller communicating with the current sensor to calculate a voltage drop associated with the cable responsive to an impedance of the cable. The controller can also control a power source output voltage responsive to the calculated voltage drop. For example, the controller can adjust the power source output voltage to minimize a cable current while maintaining a minimum motor voltage. The controller can also control a motor shaft speed by changing a power source output voltage frequency to compensate for changing slip and adjust the power source output voltage to minimize the cable current while maintaining a minimum motor voltage.

Abstract: A device and method can detect, and also break, an occurrence of gas lock in an electrical submersible pump assembly in a well bore based upon surface or downhole data without the need for operator intervention. To detect an occurrence of gas lock, an instantaneous value is monitored using a sensor. Then a controller compares the instantaneous value to a threshold value over a predetermined duration to thereby detect the occurrence of gas lock in the electrical submersible pump assembly. Sensors can include, for example, a differential pressure gauge, a pressure gage located in a pump stage located toward the inlet, a fluid temperature sensor located toward the discharge, a free gas detector located near the pump discharge, an electrical resistivity gage, a flow meter located within surface production tubing, and a vibration sensor attached to a tubing string to measure a vibration signature.

Abstract: Systems and methods for reducing harmonic distortion in a power system resulting from non-linear loading on the power system. The power at an interface with a power source is measured, and then distortion in the waveforms of the supplied power is identified. Cancellation signals which cancel all or part of the distortion are then generated and injected at the interface. In one embodiment, the power is sampled to determine the waveform, and then a Fast Fourier Transform is performed on the waveform to convert it to the frequency domain. Harmonics of the fundamental frequency can then be identified, and conjugates of the harmonics generated. An inverse Fast Fourier Transform is performed on the conjugates to generate a signal which is amplified to produce the cancellation signal.

Abstract: Systems and methods for using variable speed drives to restart downhole submersible pump motors. In one embodiment, a downhole pump is controlled using a variable speed drive that includes a control system configured to detect interruptions in the operation of the pump system. After an interruption that requires the restart of the pump motor, the control system determines the reverse rotational speed of the pump motor and restarts the motor when this speed is sufficiently low. The control system may be configured to reduce the output voltage of the variable speed drive and sweep through a range of output frequencies to determine the frequency at which the current drawn by the motor is lowest. This is the frequency at which the drive's output matches the speed of the motor and the apparent impedance of the motor is highest. When the speed is low enough, the motor is restarted.

Abstract: Systems and methods for providing ride-through for interruptions in the power supplied to drives that are used to control equipment such as downhole submersible pumps. In one embodiment, a variable speed drive includes converter and inverter sections, a capacitor bank and a control system. The drive shuts down the converter section upon detecting a disruption in the AC input power and continues to generate output power by drawing on the energy stored in the capacitor bank. When the AC input power returns (or begins to return) to normal, the drive resumes operation of the converter section in a controlled manner (e.g., by presetting the firing angle of the SCR's in the converter to match the voltage across the capacitor bank.) The drive thereby limits the current that recharges the capacitor bank and prevents sudden inrushes of current that could damage the drive.