多领域统一建模仿真下压缩机测试系统的PI参数整定

PI Parameter Setting of Compressor Refrigerating Capacity Test Systems Adopting the Unified Modeling Language

为了解决压缩机测试系统惯性大、纯滞后、耦合性强、各种扰动并存使得工况不能快速稳定的问题,采用多领域统一建模语言Modelica构造了压缩机测试系统的数学模型,将齐格勒-尼科尔斯方法应用于Dymola仿真软件来确定合理的比例积分(PI)参数,其实现过程包括在保证其他元件参数不变的情况下给气路膨胀阀以阶跃激励,再断开阶跃激励给系统添加PI控制器,由此总结出了各个PI参数对排气压力、吸气过热度、吸气压力和过冷度的影响规律。结果显示:排气压力或吸气过热度超调时适当增大比例增益或减小积分增益的设定值、振荡时适当减小积分增益设定值、吸气压力超调时适当减小比例增益设定值、稳定时间过长时增大比例增益或减小积分增益设定值、过冷时适当减小比例增益和积分增益,都将有利于系统的PI控制。该结果可为工程中的PI参数整定提供参考。

Mathematical models based on the Modelica language are built to solve the problem that the compressor test system is a dynamic system with the characteristics of great inertia, pure time-delay, strong coupling and multiple disturbances,and cannot rapidly reach a stable state. The Ziegler-Nichols method is applied to the simulation software Dymola to obtain initial PI parameters. The step excitation is given in the expansion valve under the condition that the parameters of other elements are fixed to constants, and then the PI controller is added after removing the step excitation. The influences of PI parameters on the discharge pressure, the suction superheat, the suction pressure and the subcooled temperature are concluded. It is found that increasing the proportional gain or decreasing the integrating gain could be used to solve the overshoot problems of the discharge pressure and the suction superheat, and that decreasing the integrating gain is also beneficial to the shock condition. When the suction pressure is overshoot, the proportional gain should be decreased. If the response time is too long, the proportional gain should be increased or the integrating gain should be decreased. Moreover, the subcooled suction could be improved by decreasing both the proportional gain and the integrating gain. Theseresults could be considered as a reference for the practical engineering.