Investigation of the combination of Bypass system and OPC logic for ORC system stability under load reduction disturbance

Organic Rankine cycle (ORC) is recognized as a promising technology for converting the energy from low grade heat sources into electricity. From a general perspective, the ORC system mainly operates in island mode and also has a small scale power capacity. When this type of system sustains the disturbance of load reduction, the overpressure protection in drum boiler and overspeed protection in axial turbine are the two big challenges for ORC system's stability. In the present study, the configuration type by combining the bypass system and overspeed protection control (OPC) logic is proposed in ORC system for solving these problems. Firstly, the ORC unit model consisting of the drum boiler, boiler control system, axial turbine, bypass system, turbine control system and OPC logic is established. Then, the drawback and improvements of current OPC logic in China are carried out. Finally, the simulation of this configuration type of ORC system is investigated under load reduction disturbance. The results show that the proposed configuration of ORC system has excellent performance in purpose of power system stability. The axial turbine in the simulation model operates in constant pressure mode.