由张子杨、张春路（通讯作者）、肖赋（香港理工大学）合作的论文Experimental and theoretical analysis of functional controllability for multi-condenser heat pumps在Applied Thermal Engineering 2020年第171卷在线发表。论文指出了多联机系统制热模式下常规控制策略所存在的功能能控性问题，并结合系统动态模型与多变量控制理论证明了该问题的存在及其实质。提出了一种解决方案，并通过系统动态仿真进行了验证。本论文更大的意义在于提出了一种制冷系统控制的通用设计方法，对于复杂制冷系统控制尤为重要。

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论文摘要：

Multi-split air conditioning systems are finding increasing applications in both residential and commercial buildings. Control of multi-split air conditioning systems have received considerable attentions. Most studies focused on control methods for the cooling mode, while very few control methods were developed for the heating mode. A widely adopted heating control strategy for a typical multi-condenser heat pump is regulating the indoor electronic expansion valve (EXV) openings to control subcooling or supply air temperature of each indoor unit and simultaneous regulating the outdoor EXV opening to control suction superheat. We found from experimental study that this control strategy may cause unstable EXV openings and poor command-following performance. By performing functional controllability analysis, we provide a theoretical insight into the uncontrollable problem and prove that the system is functionally uncontrollable when the conventional heating control strategy is used. Based on findings from functional controllability analysis, a modified system configuration is proposed, with a refrigerant receiver added between the indoor EXVs and the outdoor EXV. The modified system proves to be functionally controllable. Moreover, simulated command-following controllability tests show that the modified system has better performance. This paper verified the ability of functional controllability analysis in detecting structural control problems for refrigeration systems, which can be used as a general method for practical applications.