Sensorless temperature control of household refrigerators based on the electric current of the compressor

The present study is aimed at putting forward a novel temperature controller (including software and hardware) for a fan-and-damper refrigerator considering the electric current drawn by the single-speed compressor as the process variable. The control algorithm consists in a dynamic reference modification of a PI controller, together with a set of empirical conjectures. In addition, a purpose-built electronic board was designed and prototyped. All experiments were performed in-house with the refrigerator placed in a climate chamber. The refrigerator was tested at two different surrounding air temperatures (16 and 25 degrees C) under pulldown, defrost recovery, and variable ambient temperature regimes. It was noted that the proposed controller was able to maintain the refrigerator temperature within +/- 1 degrees C tolerance bounds - figures like those obtained for the baseline thermistor-based temperature controller - albeit being less costly.