Method for fault tolerant control of a vapour compression system
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Solution Overview
Problem
Ambient temperature sensors in vapour compression systems are often subjected to solar heating, leading to unreliable measurements that can result in non-optimal operation and increased energy consumption.
Innovation Solution
A method that selects a time period when the ambient temperature sensor is unexposed to solar heating to obtain reliable measurements, derives model parameters based on these measurements, and uses them to operate the system, even when the sensor is exposed to solar heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ambient temperature sensor is positioned in an outdoor environment to measure ambient temperature, then the system can obtain temperature data for control purposes, but the sensor may be subjected to solar heating leading to faulty measurements
Solution Approach 1:
The system performs preliminary identification of fault-free time periods where the sensor is not exposed to solar heating, and pre-establishes a correlation model during these periods. This preliminary action allows the system to have accurate baseline data and model parameters before solar heating occurs, enabling subsequent compensation during affected periods.
Solution Approach 2:
The system continuously monitors the ambient temperature sensor readings and compares them against the correlation model predictions. When deviations are detected that indicate solar heating interference, the system uses the pre-established model to compensate and generate corrected temperature values, creating a closed-loop feedback mechanism that maintains measurement accuracy.
2Ease of operation
If the ambient temperature sensor is used continuously without considering solar heating, then the system operation is simple, but the measurements become unreliable during solar exposure
Solution Approach 1:
The system automatically identifies fault-free time periods, establishes correlation models, detects solar heating interference, and compensates measurements without requiring manual intervention. The system self-manages the entire process of maintaining measurement accuracy, making the operation simple while ensuring reliability through automated model-based compensation.
3Ease of manufacture
If model parameters are derived from measurements taken during solar heating, then the model will be inaccurate, but not deriving parameters requires selecting specific time periods
Solution Approach 1:
The system performs the model parameter derivation in advance during identified fault-free time periods when solar heating is absent. This preliminary derivation ensures accurate baseline parameters are established before any solar heating interference occurs, maintaining model accuracy while automating the process.
Solution Approach 2:
The system automatically skips the model derivation step during solar heating periods by relying on pre-established models from fault-free periods. This allows the system to rush through or bypass the potentially inaccurate parameter derivation process when solar heating is present, maintaining both simplicity and accuracy.
Data Source
AI summary
A method for controlling a vapour compression system (1) is disclosed. The vapour compression system (1) has an ambient temperature sensor (8) arranged to measure an ambient temperature. A time period during which the ambient temperature sensor (8) is unexposed to solar heating is selected. During the selected time period, measurements of the ambient temperature are obtained by means of the ambient temperature sensor (8), and measurements of at least one further parameter related to the vapour compression system (1) are obtained, while operating the vapour compression system (1). Model parameters for a model of at least a part of the vapour compression system (1) are derived, based on the obtained measurements, the model providing correlation between the ambient temperature and the at least one further parameter. Subsequently, the vapour compression system (1) is operated based on measurements of the at least one further parameter and based on ambient temperatures derived by means of the model including the derived model parameters.