Expansion Valve Control for Stable Refrigeration Cycle Response
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Solution Overview
Problem
Existing air-conditioning systems face challenges in stabilizing the refrigeration cycle due to varying environmental conditions and operation states, leading to inefficient control and potential system instability, hunting, and excessive pressure overshoot.
Innovation Solution
An air-conditioning apparatus that calculates and dynamically adjusts the control gain and control interval of the electric expansion valve based on the operating state and system configuration, optimizing the opening degree of the expansion device to minimize settling time and maintain an acceptable overshoot ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed control gain and control interval are used in PID control, then the control system is simple to implement, but the system cannot adapt to changing operation states and environmental conditions, causing instability and hunting
Solution Approach 1:
The patent applies dynamics by making the control gain and control interval variable rather than fixed. The control gain is dynamically adjusted based on the opening degree of the electric expansion valve, compressor operating capacity, and deviation from control target value. The control interval is also dynamically changed based on the same parameters, allowing the control system to adapt to changing operation states and environmental conditions, thereby resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The patent changes the parameters of the control system (control gain and control interval) based on operating conditions. By calculating and adjusting these parameters in real-time according to the opening degree of the expansion valve, compressor capacity, and control target deviation, the system achieves adaptability to different operation states without requiring complex manual reconfiguration.
2Loss of time
If control gain is increased to reduce settling time, then the response speed improves, but overshoot increases causing excessive pressure rise and requiring operation suspension
Solution Approach 1:
The patent dynamically adjusts the control gain parameter based on the opening degree of the electric expansion valve, compressor operating capacity, and deviation from control target value. This allows the control gain to be optimized for each operating condition, achieving fast response without excessive overshoot. The control interval is also adjusted to complement the control gain changes, further optimizing the balance between response speed and overshoot control.
Solution Approach 2:
The control system uses feedback from the deviation between the actual control target value and the predetermined value, along with feedback on the opening degree and compressor capacity, to continuously adjust the control gain and control interval. This feedback mechanism enables the system to respond appropriately to changing conditions while preventing excessive overshoot that would require operation suspension.
3Measurement precision
If control parameters are optimized for each specific system configuration, then control precision improves, but the time and storage required to determine constants increases significantly
Solution Approach 1:
The control system performs self-service by automatically calculating and adjusting the control gain and control interval based on real-time operating parameters (opening degree, compressor capacity, and control target deviation). This eliminates the need for extensive pre-testing and simulation for each system configuration, as the system adapts itself to optimal control parameters during operation, significantly reducing the time and storage requirements while maintaining high control precision.
Data Source
AI summary
An air-conditioning apparatus includes a time constant calculation unit that estimates a response time constant at a time when an opening degree of an expansion device is changed on the basis of specifications of a compressor that forms a refrigeration cycle of the air-conditioning apparatus, specifications of a load side heat exchanger, and an operating state quantity of the air-conditioning apparatus, a control constant calculation means that calculates at least one of a control gain of the opening degree of the expansion device and a control interval on the basis of a calculation result of the time constant calculation means, and a control constant change means that changes a control constant.