Compressor Voltage Dip Prediction and Torque Control
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Solution Overview
Problem
Gas compressors driven by electrical variable-speed drives face challenges during grid disturbances, such as voltage dips, which can lead to surge conditions, resulting in potential mechanical damage and downtime, as existing control systems often rely on preventive tripping or static timer-based ride-through logic that may not accurately predict system behavior.
Innovation Solution
A method and system that detect voltage dips, predict the future development of grid voltage and process quantities, and decide between ride-through and shut-down modes based on predicted thresholds, using models and historical data to optimize operation and minimize downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preventive tripping is activated when grid voltage falls below a threshold, then the compressor system avoids surge conditions and mechanical damage, but the system experiences unplanned shutdown and loss of productivity
Solution Approach 1:
The controller performs preliminary actions by detecting voltage dips and activating ride-through modes before surge conditions occur. The system prepares compensatory measures (increasing drive torque) in advance during the voltage dip event to maintain compressor operation and avoid shutdown, thus preserving productivity while protecting against surge.
Solution Approach 2:
The system dynamically adjusts the drive torque based on the detected voltage dip characteristics. Instead of a static trip threshold, the controller continuously monitors grid voltage and modulates the torque output in real-time to compensate for voltage reductions, enabling the system to adapt to varying grid conditions and maintain stable operation.
2Productivity
If full-torque ride-through operation is provided during voltage dips, then the compressor maintains operation and productivity, but the system requires sufficiently high grid voltages and increased input current
Solution Approach 1:
The controller changes operational parameters by adjusting the drive torque level based on the severity and duration of the voltage dip. Instead of maintaining constant full torque, the system dynamically modifies torque output to match available grid power, optimizing the balance between maintaining productivity and managing energy consumption during disturbed grid conditions.
3Reliability
If zero-torque ride-through operation is provided during voltage dips, then the system reduces energy consumption and avoids surge, but the compressor experiences shutdown and loss of productivity
Solution Approach 1:
The controller implements preliminary torque compensation during voltage dips to maintain compressor operation. By detecting the voltage dip early and immediately providing adjusted torque support, the system prevents the torque deficiency that would lead to surge conditions, thereby maintaining both reliability and productivity simultaneously.
4Device complexity
If static timer-based ride-through logic is used, then the system provides simple control logic, but it is designed for worst-case conditions and may not accurately predict actual system behavior
Solution Approach 1:
The controller implements feedback by continuously monitoring grid voltage, compressor operating parameters, and drive torque. This real-time feedback enables the system to accurately assess actual system behavior during voltage dips and dynamically adjust torque compensation, providing precise prediction and control without requiring overly complex predetermined logic.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A method of controlling a compressor system (10) comprises a gas compressor (32) and an electrical variable-speed drive (30) supplied by an electrical grid (36) and driving the gas compressor (32). A method of controlling the compressor system (10) comprises: detecting a voltage dip (12) in a grid voltage (V) supplied to the electrical drive (30) by comparing the grid voltage (V) with a voltage dip threshold; in the case, a voltage dip (12) is detected: assuming a future development (72) of the grid voltage (V); predicting a future development (84) of at least one process quantity (q) based on at least one process parameter (86) measured in the compressor system (10) and the assumption of the future development (72) of the grid voltage (V); providing the predicted future development (84) of the least one process quantity (q) to a protection system (88). The assumed future development (72) of the grid voltage (V) is based on a predefined depth and a predefined length of an average voltage dip, the predefined depth and the predefined length of the average voltage dip are determined online from a set of historical voltage dip cases, and the assumed future development (72) of the grid voltage (V) is based on an assumption of a persistence of the actual measured voltage.