变流量制冷系统中频率与电子膨胀阀开度的协同控制研究
Collaborative Control of the Frequency and Opening of Electronic Expansion Valve in Variable Refrigerant Flow Refrigeration System

针对变流量(VRF)制冷系统控制中的滞后或超调现象，本文以变频滚动转子式制冷系统为研究对象，分别通过改变压缩机频率与电子膨胀阀开度，建立了两者单独控制下的曲线拟合模型，并对不同工况下两者的同步控制方法进行了实验研究。结果表明：过热度随膨胀电子膨胀阀开度的增大而减小，在电子膨胀阀开度为28%~32%与频率为44.5~46.5 Hz时，过热度控制难度上升，通过调节冷冻水温度可改善这一状况；在一定的工况下，通过控制质量流量，可以得到频率与电子膨胀阀开度的关系式，实现电子膨胀阀开度与压缩机频率的同步控制，使系统迅速达到稳定状态。
The hysteresis or overshoot in a variable refrigerant flow (VRF) system control is studied. This study considers a variable-frequency rolling rotor refrigeration system as the research object. By changing the compressor frequency and opening of the electronic expansion valve, a curve fitting model under a separate control of the two processes was established. An experimental research on the synchronous control method of the two processes under different working conditions was carried out. The results show that the superheat decreased with the opening of the electronic expansion valve. When the electronic expansion valve opening was 28%–32% and the frequency was 44.5–46.5 Hz, the degree of superheat control became more difficult. This condition could be improved by adjusting the temperature of the chilled water. Under certain conditions, the relationship between the frequency and opening of the electronic expansion valve could be obtained by controlling the mass flow. Synchronous control of the opening degree of the electronic expansion valve and compressor frequency was achieved; thus, the system could quickly reach a stable state