直膨式太阳能热泵热水器过热度PI控制的实现

IMPLEMENTATION OF PI CONTROL FOR SUPERHEAT DEGREE OF DIRECT EXPANSION SOLAR ASSISTED HEAT PUMP WATER HEATER

从自身特性和应用要求来看,热力膨胀阀作为直膨式太阳能热泵热水器的节流元件,调节品质不高。本文以电子膨胀阀作节流元件,采用太阳辐射强度的开环比例控制与集热板过热度的闭环反馈PI控制相结合的控制方案,通过实验研究的方法逐步制定控制策略,分三种不同情况采取特定参数控制集热板出口过热度。经实验验证,可以实现典型工况下过热度的准确、稳定控制。指出,合理改进电子膨胀阀开度的控制算法,并结合变频压缩机实现对制冷剂流量的串级控制,是实现系统全年优化运行进一步的研究方向。

It is shown that thermostatic expansion valve (TEV) as throttling device can not satisfy the request of direct expansion solar assisted heat pump water heater (DX-SAHPWH).The electronic expansion valve (EEV) was adopted and combination regulation scheme including open loop propor- tional control based on solar radiation intensity and closed loop feedback PI control based on superheat degree of solar collector was determined through experimental research,special parameters were con- firmed for controlling the superheat degree of solar collector according to three different situations, respectively.This method was verified by experiment that the superheat degree of solar collector could be controlled accurately and stably.It is indicated that more proper control algorithm should be improved and variable frequency compressor (VFC) should be used in the DX-SAHPWH system to combination regulate refrigerant flow cascaded with EEV.