Variable frequency air source heat pump cold water unit and parallel control method thereof
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Solution Overview
Problem
In variable frequency air source heat pump systems, units shut down prematurely due to uniform frequency control, leading to inefficient energy use and compressor wear, and misjudgment of system requirements during startup, resulting in suboptimal water temperature management.
Innovation Solution
Implementing a parallel control method that independently controls the operating frequency of each subunit, adjusting unloading and loading based on real-time total outlet water temperature conditions to ensure desired temperatures are met, reducing energy waste and extending compressor life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform frequency control is applied to all subunits, then the control system is simple, but some subunits shut down prematurely before reaching down conversion, reducing energy efficiency
Solution Approach 1:
The patent divides the control of subunits into independent segments, where each subunit's operating frequency is controlled independently based on its own water temperature feedback rather than uniform control. This segmentation allows each subunit to operate optimally without premature shutdown, resolving the contradiction between control simplicity and energy efficiency.
Solution Approach 2:
The patent implements dynamic frequency adjustment for each subunit based on real-time water temperature feedback. The operating frequency of each subunit is dynamically modified according to its own operational state, enabling continuous optimal operation and avoiding premature shutdown while maintaining manageable control complexity through automated feedback loops.
2Speed
If all subunits are unloaded directly when water temperature reaches set point, then the response is fast, but some subunits have not reached set temperature, causing unstable operation and frequent compressor cycling
Solution Approach 1:
The patent applies local quality control by allowing each subunit to reach its own set temperature independently before unloading, rather than forcing all subunits to unload simultaneously. This ensures that each subunit's water temperature requirement is met locally, preventing unstable operation and frequent compressor cycling while maintaining fast overall system response.
3Ease of operation
If the number of subunits to be turned on is determined directly at startup, then the startup procedure is simple, but the system may misjudge requirements, leading to insufficient water temperature
Solution Approach 1:
The patent implements feedback control during startup by continuously monitoring water temperature and adjusting the number of active subunits based on actual system performance. This feedback mechanism allows the system to self-correct and accurately meet temperature requirements while maintaining a relatively simple startup procedure through automated control logic.
Data Source
AI summary
A control method includes: setting a set water temperature for each subunit, acquiring a total outlet water temperature; according to an operating mode of the unit, judging whether the total outlet water temperature meets a first unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform an unloading action; acquiring the total outlet water temperature in real time, and judging whether the total outlet water temperature meets a second unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform the unloading action; judging whether the total outlet water temperature meets a start-up loading condition in real time, and if so, controlling the first subunit with the shortest accumulative operating time of the subunits performing the unloading action to perform a start-up loading action; and judging whether the total outlet water temperature meets the start-up loading condition every a specified time.