Air Conditioner Compressor Frequency Control for Low-Load Stability
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Solution Overview
Problem
Air-conditioning apparatuses face challenges in maintaining controllability and reducing power consumption during low-performance periods, characterized by frequent compressor starting and stopping, leading to temperature fluctuations and increased energy usage, especially when operating at low compressor frequencies and small air flow rates.
Innovation Solution
The air-conditioning apparatus employs a controller that adjusts the compressor frequency control width based on indoor temperature differences and fan rotation speeds, implementing a low-performance operation with a smaller control width and a low-air-flow and low-performance operation with an even smaller control width, along with adjusted thermo-off thresholds to prevent false temperature detection and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the compressor frequency control width is reduced during low performance period, then the controllability is improved, but the power consumption cannot be sufficiently reduced due to frequent compressor starting and stopping
Solution Approach 1:
The patent applies dynamics by making the control width adaptive rather than fixed. The controller dynamically adjusts the control width based on operating conditions: using a first control width during normal operation and a second, smaller control width during low performance period when compressor frequency is at or below a predetermined value. This dynamic adjustment prevents overshoot during low-frequency operation while avoiding unnecessary compressor cycling that would increase power consumption.
Solution Approach 2:
The patent changes the control parameter (control width) based on the operating state of the system. When the compressor frequency drops to a predetermined value or below during low performance period, the controller switches from a first control width to a second control width that is smaller than the first. This parameter change ensures precise control during low-frequency operation without triggering frequent start-stop cycles that would waste energy.
2Use of energy by moving object
If the compressor operates at low frequency during low load conditions, then the power consumption is reduced, but the indoor temperature fluctuates due to frequent starting and stopping
Solution Approach 1:
The patent employs feedback control where the controller continuously monitors the compressor frequency and indoor temperature. When the compressor frequency reaches a predetermined value or below during low performance period, the controller adjusts the control width based on feedback signals to prevent temperature fluctuations that would trigger unnecessary compressor restarts, thereby maintaining temperature stability while operating at low power consumption.
Solution Approach 2:
The patent applies beforehand cushioning by pre-setting a predetermined frequency threshold and adjusting the control width before temperature fluctuations can occur. When the compressor frequency approaches the predetermined value, the controller proactively reduces the control width to prevent overshoot and subsequent temperature instability, avoiding the need for frequent compressor restarts that would increase power consumption.
Data Source
AI summary
An air-conditioning apparatus includes when the compressor frequency exceeds a set frequency, perform a normal operation in which the compressor is controlled by causing the control width to be a first control width. The controller is configured to perform, when the compressor frequency is equal to or smaller than the set frequency and a rotation speed of the indoor fan exceeds a set rotation speed, a low performance operation in which the compressor is controlled by causing the control width to be a second control width, and, when the compressor frequency is equal to or smaller than the set frequency and the rotation speed of the indoor fan is equal to or smaller than the set rotation speed, a low-air-flow and low-performance operation in which the compressor is controlled by causing the control width to be a third control width.