Control method and control system for variable-frequency compressor, and air conditioner
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Solution Overview
Problem
Existing control methods for variable-frequency compressors in air conditioning systems face issues with compressor demagnetization and reliability due to excessive current, leading to periodic fluctuations and reduced capacity, as they either limit frequency too narrowly or broadly, affecting user comfort and system performance.
Innovation Solution
A control method that acquires and monitors the operation current and frequency of the compressor, entering a frequency-limited mode when the current exceeds a preset threshold, and gradually increases frequency when conditions allow, using predefined frequency tap positions and step sizes to finely adjust the output frequency, preventing demagnetization and maintaining optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency output is limited when the compressor current exceeds a certain value, then the compressor is protected from demagnetization and excessive current damage, but the normal capacity output of the air conditioning system is limited and user comfort is influenced
Solution Approach 1:
The patent implements dynamic frequency control by transitioning from static frequency limitation to dynamic adjustment. The controller continuously monitors current and adjusts frequency in real-time based on actual operating conditions, allowing the system to operate at higher frequencies when current is acceptable and limiting frequency only when necessary, thus maintaining both reliability and productivity
Solution Approach 2:
The patent changes the control parameter from binary frequency limitation to continuous frequency adjustment. By introducing multiple frequency levels and gradual adjustment mechanisms, the system can optimize the balance between current control and capacity output, improving both compressor protection and system performance
2Productivity
If the frequency is increased and decreased repeatedly when the current range for limiting is too small, then the system attempts to maintain capacity output, but periodic fluctuations occur and system reliability is influenced
Solution Approach 1:
The patent applies beforehand cushioning by setting hysteresis bands and dead zones in the frequency control logic. These buffers prevent the controller from reacting to minor current fluctuations, avoiding repeated frequency adjustments and the associated periodic fluctuations that would compromise system reliability
Solution Approach 2:
The patent implements feedback control by continuously monitoring current and using this information to adjust frequency. The feedback mechanism includes threshold-based control and gradual adjustment logic that prevents oscillatory behavior, ensuring stable operation and improved reliability
3Reliability
If the frequency output is limited to a lower frequency point, then the compressor current is reduced and demagnetization is prevented, but the refrigeration and heating effects of the air conditioning system are influenced
Solution Approach 1:
The patent uses dynamic frequency adjustment to maintain optimal temperature performance. By continuously adapting frequency to current conditions and using gradual adjustment mechanisms, the system minimizes the impact on refrigeration and heating effects while still providing effective compressor protection
Solution Approach 2:
The patent applies preliminary action by implementing predictive control strategies. The controller anticipates current increases and adjusts frequency proactively, and by using gradual adjustment, it allows the system to adapt smoothly, minimizing the impact on temperature performance while maintaining compressor protection
Data Source
AI summary
The control method and system for the variable-frequency compressor includes: acquiring an operation current and an operation frequency of the variable-frequency compressor; determining that the operation current is greater than or equal to a preset frequency-limited current, and reducing the operation frequency to a preset frequency-limited frequency so as to enable the variable-frequency compressor to enter a frequency-limited mode; detecting an operation current at the moment of the variable-frequency compressor every preset duration; determining that the operation current at the moment meets a preset up-conversion condition, and increasing an operation frequency at the moment of the variable-frequency compressor by a preset up-conversion frequency step size until the variable-frequency compressor retreating from the frequency-limited mode; and determining that the operation current at the moment does not meet the preset up-conversion condition, and controlling the variable-frequency compressor to maintain the operation frequency at the moment.