VFD Compression Efficiency Online Optimization for HVACR Systems
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Solution Overview
Problem
Existing HVACR systems with variable-frequency drives (VFDs) face inefficiencies due to competing power and efficiency losses in components like the drive, motor, and compressor, which are not optimally managed by traditional preprogrammed look-up tables, leading to suboptimal compression efficiency.
Innovation Solution
An online optimization method adjusts key inputs such as inverter PWM switching, carrier frequency, motor cooling, and drive cooling based on real-time operating conditions using machine learning techniques to optimize VFD compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If preprogrammed look-up tables are used to optimize drive efficiency, then drive efficiency can be improved, but the system cannot adapt to changing operating conditions and component interactions
Solution Approach 1:
The patent implements dynamic optimization by continuously adjusting VFD inputs based on real-time compression efficiency measurements and operating conditions. Instead of static preprogrammed look-up tables, the system dynamically modifies PWM switching frequency, PWM pattern, motor cooling, and drive cooling inputs to adapt to changing operating conditions and maximize compression efficiency at any given operating point.
Solution Approach 2:
The system employs feedback mechanisms by measuring actual compression efficiency and using this information to adjust VFD inputs. The controller continuously monitors system performance and modifies drive parameters based on measured outcomes, creating a closed-loop control system that adapts to varying operating conditions and component states.
2Temperature
If PWM switching frequency is reduced to decrease heating in the VFD, then drive heating is reduced, but compression efficiency deteriorates
Solution Approach 1:
The patent changes multiple parameters simultaneously rather than adjusting a single parameter in isolation. When VFD heating needs to be reduced, the system doesn't simply increase PWM switching frequency; instead, it coordinates adjustments across PWM pattern, motor cooling inputs, and drive cooling inputs to achieve the desired thermal management while maintaining compression efficiency.
Solution Approach 2:
The system introduces intermediate control variables including motor cooling and drive cooling inputs that act as mediators between PWM switching parameters and final heating outcomes. These intermediate controls allow the system to manage thermal effects without directly compromising compression efficiency through suboptimal PWM settings.
3Temperature
If motor cooling is increased to control motor heating, then motor temperature is controlled, but compression efficiency is reduced due to cooling re-compression
Solution Approach 1:
The system applies partial cooling rather than excessive cooling by precisely controlling the motor cooling input to provide just enough cooling to manage motor temperature without causing significant re-compression losses. The optimization algorithm determines the optimal cooling level that balances thermal management needs against compression efficiency preservation.
Solution Approach 2:
The patent coordinates multiple parameter changes including PWM switching frequency, PWM pattern, and drive cooling inputs alongside motor cooling adjustments. This multi-parameter approach allows the system to manage motor heating while compensating for potential re-compression losses through coordinated adjustments in other system parameters.
4Stability of the object's composition
If shaft elongation occurs in the compressor, then misalignment of the impeller happens, but traditional systems cannot compensate for this mechanical degradation
Solution Approach 1:
The system performs self-diagnosis and self-optimization by continuously measuring compression efficiency and automatically adjusting VFD inputs to compensate for mechanical degradation. The controller detects performance changes indicative of shaft elongation or impeller misalignment and autonomously modifies drive parameters to maintain optimal efficiency without requiring external intervention or mechanical adjustment.
Solution Approach 2:
The patent implements feedback control by measuring actual compression efficiency and using this information to detect and compensate for mechanical degradation. The system continuously monitors performance metrics and adjusts VFD inputs based on measured outcomes, enabling real-time compensation for shaft alignment issues and other mechanical changes.
Data Source
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AI summary
A method for adjusting compression efficiency for an HVACR system having a variable-frequency drive (VFD) is disclosed. The method includes determining a first compression efficiency, determining an operating point, determining a region of an operating map when a difference between the operating point and a previously determined operating point exceeds a predetermined threshold, adjusting a VFD input to a first input based on the region of the operating map, and controlling the VFD using the first input for a predetermined period of time. The method also includes determining a second compression efficiency and an operation restriction, adjusting the VFD input to a second input based on the operation restriction and a difference between the first compression efficiency and the second compression efficiency, and controlling the VFD using the second input. The method also includes utilizing machine learning control techniques to control several system variables to optimize the compression efficiency.