A control method based on optimal flow rate for fuel cell cogeneration waste heat utilization system with auxiliary heat transfer loop

This paper focuses on a 78kW fuel cell cogeneration system. Firstly, a waste heat utilization system including an auxiliary heat exchange loop and its model are introduced. Then a model-based feedforward plus PI feedback control method based on optimal flow rates of two sides of the heat exchanger is proposed to ensure the cooling water temperature of the fuel cell stack and the temperature of the heated water on the cold end. Finally, the effectiveness of the control method under different stack power is verified by simulating. According to the simulation analysis, the control error of the cooling water of the stack is within 1 °C and the dynamic process of the step can occur within 120s. The efficiency of the combined heat and power (CHP) system can reach 86.2%. The control method can help ensure the normal operation of fuel cells and make full use of waste heat.