Control device and method for refrigeration cycle device
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Solution Overview
Problem
Existing methods for controlling the opening degree of expansion valves in refrigeration cycle apparatuses result in reduced responsiveness and energy efficiency due to mismatched compressor frequency and valve opening, leading to prolonged discharge temperature stabilization and energy wastage.
Innovation Solution
A control device that calculates proportionality and integral coefficients based on refrigerant flow rate, allowing for differential variation ranges to improve responsiveness and match compressor frequency with expansion valve opening, thereby enhancing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If corrections in proportional action and integral action are performed at the same ratio, then the control structure is simple, but the responsiveness of discharge temperature to expansion valve opening degree deteriorates
Solution Approach 1:
The patent applies dynamics by making the control parameters (proportional and integral coefficients) variable rather than fixed. The coefficients are dynamically adjusted based on the operating frequency of the compressor, allowing the control system to adapt to changing load conditions and maintain optimal responsiveness across the entire operating range.
Solution Approach 2:
The patent changes the parameters of the control system by introducing frequency-dependent correction coefficients. The proportional coefficient and integral coefficient are modified based on the compressor's operating frequency, transforming the control system from a static to a adaptive parameter structure that optimizes performance at different operating points.
2Stability of the object's composition
If the variation range of proportional and integral coefficients is limited, then the system is stable, but the responsiveness over wide load range deteriorates
Solution Approach 1:
The patent implements dynamics by introducing frequency-based adaptation of control coefficients. The system automatically adjusts the proportional and integral coefficients according to the compressor's operating frequency, enabling it to maintain both stability at each operating point and adaptability across the full load range.
Solution Approach 2:
The patent employs parameter changes by making the control coefficients frequency-dependent. Different operating frequencies correspond to different optimal coefficient values, allowing the system to adapt its parameters to match the dynamic characteristics of the refrigeration cycle at various load conditions.
3Stability of the object's composition
If the discharge temperature control is slow, then the system is stable, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by adjusting the control coefficients based on operating frequency. This allows the system to achieve faster and more efficient temperature control at different load levels, reducing the time and energy required to reach and maintain the target discharge temperature while preserving stability through frequency-appropriate parameter selection.
Data Source
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AI summary
A control device of a refrigeration cycle apparatus includes an expansion-valve control unit configured to output an opening-degree command for an expansion valve on the basis of a discharge-temperature deviation between a discharge temperature of refrigerant discharged from a compressor and a set discharge temperature, and at least two types of control parameters including a proportionality coefficient and an integral coefficient, a flow-rate-correction-coefficient calculating unit configured to calculate a flow-rate correction coefficient from a refrigerant flow rate of refrigerant circulating through a refrigerant circuit and a preset flow-rate reference value, and a coefficient correcting unit configured to calculate the proportionality coefficient by correcting a preset proportionality-coefficient reference value on the basis of the flow-rate correction coefficient, and calculate the integral coefficient by correcting a preset integral-coefficient reference value on the basis of the flow-rate correction coefficient. The coefficient correcting unit is configured to calculate the proportionality coefficient and the integral coefficient such that a variation range of the integral coefficient within a variation range of the refrigerant flow rate is larger than a variation range of the proportionality coefficient within the variation range of the refrigerant flow rate.