冷冻水系统对于商业建筑中的暖通空调系统具有显著的功耗。该系统主要由三部分组成:空气处理机组、冷却塔和冷却器。制冷机是必不可少的部件，它们的运行消耗大量的电力。由于该系统耗电量巨大，提高其效率将带来显著的节能效益。由于系统特性和运行条件在实践中可能会发生巨大变化，无模型自寻优控制在实践中具有重要意义。在本研究中，所研究的冷冻水装置由一台螺杆式冷水机组和一台逆流式冷却塔组成。采用基于多变量牛顿的极值搜索控制（ESC）方案，在满足冷负荷的情况下，实时最大化功率效率。ESC控制器的反馈是制冷机压缩机、冷却塔风扇和冷凝器水泵的总功率，而输入是冷却- 塔风机转速和冷凝器回路水流量。采用基于Modelica的冷却塔系统动态仿真模型，对基于牛顿法的双输入ESC控制器进行了仿真。两个内环PI控制器用于调节蒸发器过热温度和消耗器在各自设定点处的出水温度。通过一个模拟案例验证了所提控制策略的有效性，在测试条件下，冷水厂的功耗从433.58 HP（323.32 kW）降至370.75 HP（276.47 kW）。能源效率提高了14.5%。利用积分性能指标对该控制策略的暂态和稳态性能进行了仿真研究。引用:ASHRAE论文:2015年ASHRAE年会，伊利诺伊州芝加哥

The chilled water systems have significant power consumption for HVAC systems in commercial buildings. The systems mainly consists three components: air handling unit, cooling tower and chillers. Chillers are the essential components, and their operation consumes considerable power consumption. Due to the significant power consumption of such system, improvement of its efficiency would lead to significant benefit in energy saving. As the system characteristics and operational conditions can vary dramatically in practice, model-free self-optimizing control is of high interest in practice. In this study, the chilled-water plant being studied consists of one screw chiller and one counter-flow cooling tower. A multi-variable Newton-based extremum seeking control (ESC) scheme is applied to maximize the power efficiency in real time with the cooling load being satisfied. The feedback for the ESC controller is the total power of the chiller compressor, the cooling tower fan and the condenser water pump, while the inputs are cooling-tower fan speed and the condenser-loop water flow rate. The two-input Newton-based ESC controller is simulated with a Modelica based dynamic simulation model of the chiller-tower system. Two inner-loop PI controllers are used to regulate the temperatures of evaporator superheat and consender leaving water at their respective setpoints. The effectiveness of the proposed control strategy is validated with a simulation case with power consumption of chilled water plant reduced from 433.58 HP (323.32 kW) to 370.75 HP (276.47 kW) under tested conditions. The energy efficiency increase is 14.5%. More simulations are performed to investigate the transient and steady state performance of proposed control strategy using integral performance indices.