Variable refrigerant flow system with sub-cooling temperature optimization using extremum-seeking control
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Solution Overview
Problem
Variable refrigerant flow (VRF) systems face challenges in optimizing power consumption and operational efficiency due to the complexity of dynamic and time-varying conditions in building heating and cooling processes, where existing control strategies lack the ability to dynamically adjust to minimize energy usage effectively.
Innovation Solution
The implementation of extremum-seeking control (ESC) in VRF systems, which uses a sub-cooler and a bypass expansion valve to generate a sub-cooling temperature setpoint by perturbing the current value with an excitation signal, monitoring power consumption, estimating gradients, and adjusting the setpoint to drive the power consumption towards an extremum, thereby optimizing the operation of outdoor VRF units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional control strategies are used in VRF systems, then the system operation is simple to implement, but the power consumption cannot be dynamically optimized effectively
Solution Approach 1:
The patent implements extremum-seeking control (ESC) that continuously monitors power consumption and dynamically adjusts the sub-cooling temperature setpoint based on feedback signals. The controller perturbs the setpoint, measures the resulting power consumption changes, and uses gradient information to drive the system toward optimal operating conditions, achieving dynamic power optimization through closed-loop feedback
Solution Approach 2:
The patent dynamically changes the sub-cooling temperature setpoint parameter to optimize power consumption. By treating the setpoint as a variable parameter rather than a fixed value, the system can adapt to changing operating conditions and continuously seek optimal performance points through controlled parameter variation and gradient-based adjustment
2Adaptability or versatility
If the sub-cooling temperature setpoint is fixed, then the control system is simple to operate, but the system cannot adapt to dynamic operating conditions for optimization
Solution Approach 1:
The patent implements a self-optimizing control system where the extremum-seeking controller automatically adjusts the sub-cooling temperature setpoint without requiring manual intervention. The system perturbs the setpoint, monitors power consumption responses, estimates gradients, and autonomously drives the operation toward optimal conditions, making the system adapt to changing conditions while maintaining ease of operation
Solution Approach 2:
The patent transforms the static sub-cooling temperature setpoint into a dynamic variable that automatically adapts to changing operating conditions. The ESC controller continuously modifies the setpoint based on real-time power consumption measurements and gradient estimates, enabling the system to track optimal operating points as conditions change while maintaining simple operation through automation
3Loss of energy
If extremum-seeking control is implemented to optimize power consumption, then energy efficiency is improved, but the control system complexity increases
Solution Approach 1:
The patent applies extremum-seeking control specifically to the sub-cooling temperature setpoint parameter rather than the entire VRF system. By focusing optimization efforts on this single critical parameter, the system achieves significant energy efficiency improvements while limiting control complexity to a manageable scope, avoiding the need for comprehensive system-wide optimization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for dynamic optimization of power consumption, reducing energy usage by identifying optimal operating conditions for the VRF system, leading to improved efficiency and cost savings in building heating and cooling processes.
Implementation Method 1
the sub-cooler includes a first flow path and a second flow path configured to pass through a heat exchanger
Implementation Method 2
a bypass expansion valve configured to control a flow of the refrigerant through the sub-cooler
Data Source
AI summary
A variable refrigerant flow (VRF) system for a building. The VRF system includes at least one outdoor VRF unit configured to heat or cool a refrigerant for use in heating or cooling the building. The at least one outdoor VRF unit includes a sub-cooler and a bypass expansion valve configured to control a flow of the refrigerant through the sub-cooler and an extremum-seeking controller configured to generate a sub-cooling temperature setpoint for the at least one outdoor VRF unit. The extremum-seeking controller is configured to determine a total power consumption of the at least one outdoor VRF unit, generate a sub-cooling temperature setpoint for the at least one outdoor VRF unit using an extremum-seeking control technique that drives the total power consumption toward an extremum, and use the sub-cooling temperature setpoint to operate the at least one outdoor VRF unit.