Compressor control for increased efficiency
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Solution Overview
Problem
Existing compressor systems either rely solely on variable frequency drives (VFDs) or mechanical unloaders to reduce capacity, leading to inefficiencies and energy wastage, as they are typically used sequentially rather than in combination, which limits energy savings to less than 5%.
Innovation Solution
A control system and method that integrates both VFDs and mechanical unloaders to adjust compressor speed and capacity simultaneously, using operational parameters like suction and discharge temperatures to optimize efficiency by selecting efficient combinations of speed and unloading, thereby reducing overcompression and enhancing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If VFDs and mechanical unloaders are used separately or sequentially, then device complexity is reduced, but energy efficiency deteriorates
Solution Approach 1:
The patent combines VFD speed control and mechanical unloader capacity control into a single integrated control system that manages both mechanisms simultaneously. The controller receives operational parameters and coordinates both the VFD motor controller and mechanical unloader actuator to work together, achieving synergistic energy efficiency improvements of 5% or more compared to using either system alone.
2Use of energy by moving object
If compressor speed is reduced via VFD to minimum level before mechanical unloading, then capacity control is simplified, but energy efficiency deteriorates
Solution Approach 1:
The patent implements dynamic coordination between VFD speed control and mechanical unloader positioning. Rather than following a fixed sequence, the controller continuously adjusts both parameters based on real-time operational conditions, allowing the system to operate at optimal efficiency points across the entire operating range. This dynamic approach enables efficient operation at any capacity level without requiring reduction to minimum speed first.
Solution Approach 2:
The system simultaneously varies multiple parameters - motor speed frequency and mechanical unloader position - to achieve optimal efficiency. The controller manages both parameters concurrently, changing them in coordinated fashion based on operational demands, rather than changing one parameter after the other in a sequential manner.
3Use of energy by moving object
If mechanical unloaders are used alone, then device complexity is reduced, but energy efficiency deteriorates
Solution Approach 1:
The patent merges the control functions of VFD and mechanical unloaders into a unified control architecture. The single controller integrates inputs from operational sensors and coordinates both the motor speed control and unloader positioning, achieving improved energy efficiency while managing system complexity through integration rather than separate control systems.
4Productivity
If compressor capacity exceeds load, then productivity is improved, but energy efficiency deteriorates due to overcompression
Solution Approach 1:
The controller continuously monitors operational parameters including temperature, pressure, and capacity metrics. When capacity exceeds load conditions are detected, the system provides feedback control by adjusting mechanical unloader position and/or motor speed to reduce capacity and eliminate overcompression, thereby maintaining energy efficiency while meeting load demands.
Solution Approach 2:
The system dynamically adjusts operational parameters - specifically motor speed frequency and unloader position - in response to capacity versus load conditions. When overcompression is detected, the controller changes these parameters to reduce capacity to match load requirements, optimizing the balance between productivity and energy efficiency.
Data Source
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AI summary
Control systems and methods for increasing efficiency of a compressor while the compressor capacity exceeds compressor load, by using a mechanical unloader such as a slide valve to reduce the internal volume ratio of the compressor and allow a more efficient speed to be maintained by a variable frequency drive (VFD) while reducing the compressor capacity based on the load. Control systems include the VFD, a controller for the VFD and the mechanical unloader, and temperature sensors. Compressor embodiments further include one or more compressors and mechanical unloaders operated by the control systems.