Control device for refrigeration cycle apparatus, and control method for refrigeration cycle apparatus, and refrigeration cycle apparatus
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Solution Overview
Problem
Existing control methods for refrigeration cycle apparatuses result in reduced responsiveness of the discharge temperature of the compressor relative to the opening degree of the expansion valve, leading to energy wastage and deterioration in energy saving properties, especially in transient states due to mismatched operating frequencies and valve openings across varying loads.
Innovation Solution
A control device that calculates proportionality and integral coefficients based on refrigerant flow rates to adjust the opening degree command for the expansion valve, ensuring a larger variation range for the integral coefficient compared to the proportionality coefficient, thereby improving responsiveness and matching compressor frequency with valve opening over a wide load range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If corrections in proportional action and integral action are performed at the same ratio based on discharge temperature deviation, then the control structure remains simple and easy to implement, but the responsiveness of discharge temperature to expansion valve opening degree deteriorates, especially in transient states
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. This resolves the contradiction by enabling responsive control in transient states while maintaining a relatively simple control structure through automated parameter adjustment.
Solution Approach 2:
The patent changes the parameters of the control system by introducing operating frequency-dependent correction coefficients. The proportional coefficient and integral coefficient are modified based on the current operating frequency, allowing the system to optimize responsiveness across different load conditions. This parameter change enables the system to maintain good responsiveness in transient states without complicating the overall control architecture.
2Adaptability or versatility
If the variation range of proportional and integral coefficients remains fixed across all load ranges, then the control parameters are easy to set and maintain, but the mismatch between compressor operating frequency and expansion valve opening degree increases, leading to energy wastage
Solution Approach 1:
The patent makes the control parameters dynamic by linking them to the operating frequency of the compressor. The proportional and integral coefficients are adjusted in real-time based on the current operating conditions, enabling the system to adapt to varying load demands. This dynamic adaptation prevents energy wastage by ensuring the expansion valve opening degree appropriately matches the compressor frequency across all operating ranges.
Solution Approach 2:
The patent implements feedback by using the operating frequency as a basis for adjusting the control coefficients. The system continuously monitors the operating frequency and uses this information to modify the proportional and integral coefficients, creating a closed-loop control mechanism that adapts to changing conditions and prevents energy inefficiency.
Data Source
AI summary
A refrigeration cycle apparatus controller includes an expansion-valve controller configured to output an opening-degree command for an expansion valve based on a deviation between a discharge temperature of refrigerant discharged from a compressor and a set discharge temperature, and at least two control parameters including a proportionality coefficient and an integral coefficient, a flow-rate-correction-coefficient calculator 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 corrector configured to calculate the proportionality coefficient by correcting a preset proportionality-coefficient reference value based on the flow-rate correction coefficient, and calculate the integral coefficient by correcting a preset integral-coefficient reference value based on the flow-rate correction coefficient. The proportionality coefficient and the integral coefficient are calculated such that a variation range of the integral coefficient rate is larger than a variation range of the proportionality coefficient.