Control of superheat of gas engine heat pump using variable universe fuzzy Proportional-Integral-Differential

[Display omitted] •A variable universe fuzzy PID control algorithm is proposed for the superheat.•The combined model of electronic expansion valve and evaporator is established.•Simulation and experimental verification are implemented.•The proposed control method has strong robustness and fast regulation. Gas engine heat pump (GEHP) is more and more widely used in various commercial buildings and residential buildings because of its advantages of high efficiency, energy saving and environmental protection. However, unstable superheat is easy to cause unstable operation of GEHP system, resulting in lower energy efficiency and unnecessary energy waste. Therefore, to achieve the reliable control of superheat, a variable universe fuzzy Proportional-Integral-Differential (PID) control method is proposed in this study. First, the combined control model of electronic expansion valve (EEV) and evaporator is established. A step response curve of superheat to the opening of EEV and the parameters of the control model are obtained by experiment. In addition, simulation of the proposed control method has been performed and compared with other two methods to evaluate the control performance. Meanwhile, the proposed control method is applied to the test bench for superheat control. The results showed that the fluctuation of superheat after reaching the steady state under the control method was kept within 0.3 °C, and the superheat could return to the steady state in a short time after being disturbed. Both simulation and experiment results indicate that the proposed control method has strong robustness and fast regulation.