The cascade refrigeration system and cascade air source heat pump have both been a well-known advanced technology for providing cooling and heating under certain circumstances. The intermediate temperature has been proven as a key factor in affecting the operating performance for both the refrigeration and heat pump system. However, the optimal intermediate temperature varies along with the change of the ambient temperature, cooling/heating demand. So achieving the real-time optimal intermediate temperature in a realistic operating circumstance is critical for improving the performance of cascade refrigeration or heat pump system. In this paper, the extreme seeking control strategy is proposed to optimize the coefficient of performance via seeking the real-time optimal intermediate temperature. A cascade refrigeration system model and a cascade air source heat pump water heater model are built based on Modelica, and the ASHP water heater model is validated by experimental data. The simulations are conducted under fixed and variable operating conditions to validate the effectiveness of the proposed strategy.

级联制冷系统和级联空气源热泵都是在某些情况下提供冷却和加热的众所周知的先进技术。中间温度已被证明是影响制冷和热泵系统运行性能的关键因素。然而，最佳中间温度随着环境温度，冷却/加热需求的变化而变化。因此，在现实的操作环境中实现实时最佳中间温度对于提高级联制冷或热泵系统的性能至关重要。本文提出了一种极限寻优控制策略，通过寻找实时最优中间温度来优化性能系数。基于Modelica建立了复叠制冷系统模型和复叠空气源热泵热水器模型，并通过实验数据验证了ASHP热水器模型。仿真在固定和可变操作条件下进行，以验证所提出策略的有效性。