Adaptive control for a multi-condenser inverter heat pump system

A constant-speed heat pump is unsuitable for a multi-condenser system, owing to the impossibility of using the same compressor frequency to control individual subsystems. In the present study therefore, an inverter heat pump actuated by a variable-speed compressor was adapted for a multi-condenser system. To control the temperature of two air-conditioned rooms individually, two step-motor-driven electronic expansion valves (EEVs) were used to control the refrigerant mass flow rate. To satisfy the different conditioning requirements of the two rooms, the EEVs themselves were governed by a model reference adaptive control (MRAC) law. A test was conducted to obtain the fit function for the compressor frequency and the EEVs´ opening area, so that the compressor could be effectively controlled. A cooling cycle model, including a rotary compressor, two condensers, an EEV and an evaporator, was derived, and a simplified first-order model was used for the two air-conditioned rooms. Simulation results proved that the heat pump with the developed control strategy and algorithm is a very efficient means of achieving desirable temperature control results.