Chiller plant with dynamic surge avoidance
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Solution Overview
Problem
Centrifugal compressors in chiller systems are prone to surge, leading to energy loss, component stress, and potential failure due to existing control techniques that can push the system into operating conditions causing compressor surge, despite efforts to optimize energy consumption and costs.
Innovation Solution
A method is introduced to determine predicted surge lift temperature differences and set anti-surge condenser water temperature and flow rate limits, establishing setpoints to operate the chiller system within safe boundaries, thereby preventing compressor surge by constraining operational parameters through an anti-surge controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If optimizing controllers are used to minimize energy consumption and costs, then energy efficiency is improved, but the system may be pushed into operating conditions that cause compressor surge
Solution Approach 1:
The anti-surge controller proactively prevents compressor surge by establishing safe operating boundaries for condenser water temperature and flow rate before the system enters surge conditions. This preliminary protective action allows the optimizing controller to freely minimize energy consumption without risking compressor surge, as the anti-surge constraints act as a safety net that blocks harmful operating conditions before they occur.
Solution Approach 2:
The anti-surge controller serves as an intermediary layer between the optimizing controller and the chiller system. It receives energy-optimized setpoints from the optimizing controller, translates them into safe operating parameters by applying surge avoidance constraints, and outputs constrained setpoints to the chiller system. This intermediary function resolves the contradiction by decoupling energy optimization from surge risk.
2Productivity
If the chiller system operates at maximum efficiency, then productivity is improved, but compressor surge may occur causing energy loss and component stress
Solution Approach 1:
The control system applies different quality requirements to different aspects of operation: the optimizing controller maximizes overall cooling productivity, while the anti-surge controller applies localized safety constraints specifically to condenser water temperature and flow rate parameters. This local quality approach allows maximum productivity wherever possible, with surge protection applied only where necessary.
Solution Approach 2:
The system dynamically adjusts operating parameters (condenser water temperature setpoint and flow rate setpoint) based on real-time conditions. The anti-surge controller calculates safe parameter ranges that prevent surge while allowing the system to operate at maximum efficiency within those ranges. This parameter adaptation enables high productivity without triggering surge conditions.
3Ease of operation
If existing control techniques are used to optimize system operation, then operational efficiency is improved, but compressor surge risk increases leading to potential failure
Solution Approach 1:
The system merges two control functions into a unified control architecture: the optimizing controller that maximizes operational efficiency and the anti-surge controller that ensures reliability. Both controllers operate simultaneously with the anti-surge controller imposing constraints on the optimizing controller's outputs. This merged approach maintains ease of automatic operation while eliminating surge risk.
Solution Approach 2:
The anti-surge controller performs preliminary calculations to determine safe operating boundaries for condenser water temperature and flow rate before the optimizing controller generates setpoints. These pre-established safety constraints are then applied to the optimized setpoints, ensuring that automatic operation remains easy while reliability is guaranteed from the outset.
Data Source
AI summary
Systems, apparatus and methods for operating a chiller plant while minimizing or eliminating the occurrence of centrifugal compressor surge. Taking into account chiller design specifications and current operating conditions, a compressor lift point at which surge is predicted to occur is established. Minima and maxima for various chiller setpoints that avoid or eliminate the occurrence of compressor surge are imposed on setpoints provided by a conventional optimizing chiller controller. The chiller system is operated in accordance with the resultant anti-surge setpoints. Coolant tower flow is modulated to enable the compressor to operate at near-surge conditions while preventing the onset of actual surge.