Control method and control device for electronic expansion valve and air source heat pump system
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Solution Overview
Problem
Existing electronic expansion valves in air source heat pump systems face challenges in maintaining sufficient exhaust gas superheat degree under extreme conditions, leading to insufficient refrigerant circulation, liquid return, and reduced system reliability due to inaccurate temperature detection and temperature drifts.
Innovation Solution
A control method for electronic expansion valves that calculates target exhaust gas temperature based on compressor frequency and corrects the opening degree according to exhaust gas superheat degree comparisons, ensuring superheat requirements are met across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the electronic expansion valve opening degree is controlled according to target exhaust gas temperature in low-temperature heating mode, then the control follows standard temperature-based logic, but the temperature detection accuracy deteriorates due to temperature drift in low-temperature environments
Solution Approach 1:
The patent changes the control parameter from temperature-based to frequency-based. Instead of using exhaust gas temperature directly for control decisions, the system uses compressor frequency as the primary control parameter, which remains accurate and reliable in low-temperature environments. This resolves the temperature drift issue while maintaining effective control logic.
2Temperature
If the electronic expansion valve opening degree is continuously reduced to meet target exhaust gas temperature, then the temperature control follows the target, but the refrigerant circulation amount becomes insufficient under extreme working conditions
Solution Approach 1:
The patent introduces a feedback mechanism where the actual exhaust gas superheat degree is continuously monitored and used to adjust the electronic expansion valve opening degree. When the superheat degree falls below the preset value, the opening degree is increased to ensure sufficient refrigerant circulation, preventing system reliability issues while maintaining temperature control.
3Device complexity
If the electronic expansion valve opening degree is controlled by target opening degree, then the control simplifies to a preset value, but the sufficient exhaust gas superheat degree cannot be guaranteed in low-frequency ranges
Solution Approach 1:
The patent implements dynamic control where the electronic expansion valve opening degree is adjusted in real-time based on compressor frequency and actual exhaust gas superheat degree. Instead of using fixed target opening degrees, the system dynamically modifies the opening degree according to operating conditions, ensuring sufficient superheat degree across all frequency ranges while maintaining manageable control complexity.
4Measurement precision
If the electronic expansion valve opening degree is reduced to improve control precision, then the temperature control accuracy improves, but liquid return occurs in units and system reliability deteriorates
Solution Approach 1:
The patent uses feedback control where the actual exhaust gas superheat degree is continuously measured and compared with the preset value. The electronic expansion valve opening degree is adjusted based on this feedback to maintain sufficient superheat degree, preventing liquid return while preserving control accuracy. This ensures system reliability is maintained throughout the control process.
Data Source
AI summary
A control method and control device for an electronic expansion valve and an air source heat pump system. The control method includes obtaining a frequency of a compressor, calculating a target exhaust gas temperature according to the frequency, and controlling an opening degree of the electronic expansion valve according to the target exhaust gas temperature; and obtaining an exhaust gas superheat degree of the compressor, and correcting the opening degree of the electronic expansion valve according to a comparison result between the exhaust gas superheat degree and a preset superheat degree value, so that the exhaust gas superheat degree meets superheat degree requirements.