Fault-tolerant supervisory control of building condenser cooling water systems for energy efficiency

Abstract

This article presents a fault-tolerant supervisory control strategy for building condenser cooling water systems. The proposed strategy mainly consists of a model-based predictive control (MPC) scheme, a fault detection and diagnosis (FDD) scheme and a fault accommodation and tolerant (FAT) scheme. The MPC scheme using systematic optimization is employed to identify optimal control settings for the local process controllers. The FDD scheme is utilized to detect and diagnose major possible faults that may happen in the routine operation of condenser cooling water systems. The faults considered mainly include critical sensor faults, physical component performance degradations, and malfunctions of control logics. According to the types of faults that happen, the FAT scheme is then used to handle the faults in order to regain the control as far as possible. The performance of this strategy is tested and evaluated in a simulated virtual system representing the actual condenser cooling water system in a super high-rise building. The results show that the proposed strategy is capable of maintaining acceptable control performance and can help save about 0.18%–5.23% total energy of the chillers and cooling towers when the operation of condenser cooling water systems suffers from some faults, as compared to that using the same control strategy but without using the FAT scheme.

Acknowledgment

The research work presented in this article was financially supported by a grant of the National 11-5 program of PRC and a grant from The Hong Kong Polytechnic University as well as the support from Sun Hung Kai Real Properties Limited.

Zhenjun Ma, PhD, is Lecturer. Shengwei Wang, PhD, CEng, Member ASHRAE, is Chair Professor