ESP Cable Loss Compensation via Dynamic Voltage Control
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Solution Overview
Problem
Existing ESP systems fail to accurately control motor terminal voltage under varying load conditions due to significant cable voltage drop, leading to motor overheating, decreased efficiency, and core saturation, as prior approaches like linear or 'shaped' V/Hz curves are not responsive to all changes in well conditions.
Innovation Solution
The system actively modifies the output voltage of the variable speed drive to compensate for cable loss by calculating and directly addressing the voltage drop using motor current and complex impedance, optimizing voltage delivery to maintain proper motor terminal voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the output voltage of the variable speed drive is varied linearly with operating frequency to maintain a constant V/Hz ratio, then the motor operates efficiently at rated conditions, but the motor terminal voltage becomes too high under reduced load conditions causing motor heating and core saturation
Solution Approach 1:
The system measures the actual motor terminal voltage and feeds this information back to the variable speed drive controller. Based on the feedback signal indicating over-voltage conditions, the controller automatically adjusts the output voltage to reduce it to appropriate levels, thereby preventing motor heating and core saturation while maintaining efficient operation
Solution Approach 2:
The system dynamically changes the voltage parameter output by the variable speed drive based on actual operating conditions. Instead of maintaining a fixed V/Hz ratio, the controller modifies the output voltage parameter in response to load changes and terminal voltage measurements, optimizing motor performance across varying operating conditions
2Speed
If the motor operating speed is decreased to match production requirements, then the pump load decreases appropriately, but the motor terminal voltage becomes excessively high due to reduced cable voltage drop
Solution Approach 1:
The feedback mechanism continuously monitors motor terminal voltage and communicates this information to the variable speed drive controller. When speed reduction causes excessive terminal voltage, the feedback signal triggers controller adjustment of the output voltage parameter to compensate for the reduced cable voltage drop, maintaining appropriate terminal voltage levels
Solution Approach 2:
The system transitions from a static V/Hz control approach to a dynamic control method where the output voltage parameter is continuously adjusted based on real-time operating conditions. This dynamic adjustment allows the system to maintain optimal terminal voltage across varying speeds and load conditions
3Object-affected harmful factors
If a shaped V/Hz curve is used instead of a linear curve to mitigate voltage issues, then motor terminal voltage is improved under expected load conditions, but the system remains unresponsive to unexpected changes in well conditions and motor load
Solution Approach 1:
The feedback-based control system continuously measures actual motor terminal voltage and adjusts the output voltage parameter in real-time based on actual operating conditions. This allows the system to adapt to unexpected changes in well conditions and motor load, overcoming the limitations of predetermined shaped V/Hz curves that cannot respond to unforeseen conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves efficiency, reduces motor heating, and prevents core saturation by accurately controlling voltage at the motor terminals, enhancing overall system performance and reducing lifecycle costs.
Implementation Method 1
determining an impedance of a cable in an electrical submersible pumping system... calculating a voltage drop associated with the cable
Data Source
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AI summary
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.