Coordinated DOAS-VRF Controller for Cycling Loss Reduction
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Solution Overview
Problem
The operation of combined air-conditioning systems, such as dedicated outdoor air systems (DOAS) and variable refrigerant flow (VRF) systems, faces challenges in achieving energy efficiency due to independent control strategies, leading to dynamic system cycling losses and temperature fluctuations, especially when the VRF system is not coordinated with the DOAS system.
Innovation Solution
A centralized control system that jointly controls dependent components, like compressors, and independently controls independent components, such as expansion valves, using multi-variable and single-variable regulators to synchronize setpoints and minimize energy consumption by optimizing fan speeds and compressor frequencies across both systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple air-conditioning systems (DOAS and VRF) operate independently with separate control strategies, then each system can maintain its own setpoint requirements, but the combined system experiences dynamic cycling losses, temperature fluctuations, and reduced energy efficiency
Solution Approach 1:
The patent merges the control of DOAS and VRF systems into a unified control framework where a central controller coordinates the operation of both systems. The controller integrates setpoint management, allowing the systems to operate cooperatively rather than independently, thereby eliminating cycling losses and improving energy efficiency while maintaining reliable operation.
Solution Approach 2:
The control system is designed to universally manage multiple types of air-conditioning equipment (both DOAS and VRF systems) through a single controller that can handle different system configurations and operational requirements. This multi-functional approach enables coordinated control across diverse system components, resolving the contradiction between independent operation and energy efficiency.
2Adaptability or versatility
If a VRF system is added to a DOAS system to increase cooling capacity and performance, then the overall system capability is enhanced, but the system complexity and difficulty of coordinated operation increase due to additional degrees of freedom
Solution Approach 1:
The patent segments the control functions into distinct modules: setpoint management, operational coordination, and system-specific control. By dividing the complex control task into manageable segments, the system can handle multiple air-conditioning systems with different capabilities without becoming unmanageably complex, thus maintaining high adaptability while controlling complexity.
Solution Approach 2:
The central controller acts as an intermediary between the DOAS and VRF systems, mediating their interactions and coordinating their operations. This intermediary approach allows the systems to work together effectively, managing the increased complexity introduced by combining different system types while maximizing their combined performance capability.
3Measurement precision
If DOAS controls supply air temperature to a setpoint while VRF regulates space temperature to a different setpoint, then each system meets its specific control objective, but uncordinated operation causes temperature fluctuations and cycling losses
Solution Approach 1:
The patent implements feedback mechanisms where the central controller continuously monitors the operational status and temperature readings from both DOAS and VRF systems. Based on this feedback, the controller dynamically adjusts setpoints and operational parameters to coordinate the systems, ensuring that their combined effect maintains stable temperatures without causing cycling losses, while still meeting the precise temperature control requirements of each system.
Data Source
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AI summary
The present invention relates to a controller controls a first air-conditioning system and a second air-conditioning system having separate refrigerant circuits, but arranged for conditioning a common space. The controller includes a multi-variable regulator to determine control signals for controlling operations of first components of the first and the second refrigerant circuits to reduce jointly and concurrently an environmental error between setpoint and measured values of environment in the common space. The controller also includes at least two single-variable regulators to receive operational errors between setpoint and measured values of an operation of a second component of the first and the second refrigerant circuits. The controller separately determines control signals for controlling the operation of different refrigerant circuits that reduce the operational errors. The controller also includes a lookup table that stores values for other inputs of the systems that improve its performance, and which selects specific input values for both systems according to the outputs of the multi-variable and/or single variable regulators. The controller includes an electrical circuit for controlling the first and the second air-conditioning systems according to the determined control signals.