Method for controlling a refrigeration device
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Solution Overview
Problem
Refrigeration systems with variable speed compressors and fans in high-performance applications face issues with compressor restart speed over-responses and energy inefficiencies due to rapid on/off cycling, which leads to increased wear and energy consumption, and requires complex tuning of control algorithms.
Innovation Solution
The implementation of an Integrating Speed Response Damping Factor (IDF) to prevent compressor restart speed over-responses and the use of an Error Offset to simplify the tuning of PID control systems, along with a Continuous Calibration Factor to adjust for thermal load changes and disturbances, which helps in modulating the point of oscillation and improving system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a variable speed compressor is used to reduce energy consumption and wear, then compressor life and energy efficiency are improved, but the system may experience rapid on/off cycling that increases wear and energy consumption
Solution Approach 1:
The controller applies a damping factor to the compressor output signal before restart to prevent excessive restart speed. This preliminary counteraction reduces the likelihood of rapid on/off cycling by dampening the overshoot that would otherwise cause the compressor to cycle too quickly, thereby maintaining reliability while preserving energy efficiency benefits
Solution Approach 2:
The system uses feedback control where the controller continuously monitors compressor operation and adjusts the output signal based on system response. This feedback mechanism prevents rapid cycling by detecting when damping is needed and applying appropriate corrections to maintain stable operation
2Stability of the object's composition
If a damping factor is applied to prevent compressor restart speed over-response, then compressor restart stability is improved, but the control algorithm complexity increases
Solution Approach 1:
The damping factor is implemented as a simple parameter adjustment to the compressor output signal rather than a complex control algorithm. By changing the parameter (applying a damping multiplier) rather than redesigning the entire control system, the patent achieves improved restart stability while minimizing increases in control algorithm complexity
Data Source
AI summary
A method for controlling a refrigeration device including a variable speed compressor and variable speed evaporator and condenser fans includes modifying a PID control scheme by calculating a factor to reduce the restart speed of the compressor depending on the length of time the compressor was at rest, and modulating the point of oscillation of the control process.