Downhole Generator Overvoltage Protection via Controller
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Solution Overview
Problem
Downhole generators experience overvoltage issues due to turbine speed exceeding rated speed, leading to potential damage to electronic components and delays in hydrocarbon production as damaged components require drill string retrieval for servicing.
Innovation Solution
Incorporating a controller with machine-readable mediums to monitor operational characteristics, activate overvoltage protection by adjusting d-axis and q-axis current components, and potentially shutting down the generator to prevent damage, while maintaining rated power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the turbine operates above rated speed due to high fluid flow rate, then the generator produces higher voltage, but the electronic components experience overvoltage and may be damaged
Solution Approach 1:
The controller dynamically changes the electrical parameters (d-axis current, q-axis current) to control the output voltage and torque of the generator, preventing overvoltage damage while utilizing high fluid flow rates
2Productivity
If the turbine operates above rated speed, then more electrical power is generated, but the power convertor and load experience overvoltage conditions
Solution Approach 1:
The controller continuously monitors the generator output and adjusts the d-axis and q-axis current components based on feedback signals to maintain voltage within safe limits while maximizing power generation from high fluid flow rates
Solution Approach 2:
The controller dynamically changes the electrical parameters (d-axis current, q-axis current) to control the output voltage and torque of the generator, preventing overvoltage damage while utilizing high fluid flow rates
3Reliability
If electronic components are damaged due to overvoltage, then the generator must be serviced by pulling out the drill string, but this causes delays in hydrocarbon production
Solution Approach 1:
The controller applies preliminary protective action by detecting and responding to overvoltage conditions before they cause component damage, using d-axis and q-axis current control to prevent the harmful effects that would require costly and time-consuming repairs
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
Effectively protects downhole generators and electronics from overvoltage by limiting voltage and torque, preventing component damage and reducing downtime by allowing continuous operation within rated parameters even at elevated turbine speeds.
Implementation Method 1
The downhole generator also includes an alternator that is coupled to the turbine and is operable to convert kinetic energy generated by the turbine to electrical energy in the form of an alternating current
Implementation Method 2
The downhole generator may further include a power convertor or similar component operable to convert the alternating current into direct current to power downhole electronics (load)
Data Source
AI summary
The disclosed embodiments include a method to protect a downhole generator from overvoltage. In one embodiment, the method includes determining a speed of an alternator. The method also includes activating overvoltage protection mode if the speed of the alternator is greater than a threshold speed, where activating the overvoltage protection mode includes converting an alternating current measured at the alternator into a first component and a second component of a direct current. Activating the overvoltage protection mode also includes determining a first current threshold based on at least one component of the downhole generator. Activating the overvoltage protection mode also includes shutting down the downhole generator if the first component of the direct current is greater than the first current threshold and decreasing a magnetic flux of the downhole generator if the first component of the direct current is not greater than the first current threshold.