With the progressive accumulation of reactor-years for the multi-module high temperature gas-cooled reactor (mHTGR), exemplified by its first global implementation as the HTR-PM in Shidao Bay, Rongcheng city, Shandong Province, China in 2023, it becomes imperative to address potential incidents under abnormal working conditions such as reactor trip (RT, or SCRAM) or turbine trip. To ensure that the reactors remain in a safe state, this paper outlines a corresponding control strategy for each potential incident following a comprehensive sequence of RT or turbine trip incidents using the mHTGR model developed previously on the MATLAB®/Simulink® platform (Dong et al. in Energy 155:971–991, 2018; Dong et al. in Desalination 456:121–135, 2019; Dong in Energy Convers. Manage. 272:1–19, 2022). The control actuators at our disposal include the main steam valve, the main feedwater pump, and the main feedwater regulating valve(s) etc. Under normal working conditions, the pressure of the main steam is controlled by the main steam valve, and the mass flow rate of each mHTGR is controlled by the main feedwater regulating valve while the main feedwater pump is working at constant speed (Dong et al. in IEEE Trans. Nucl. Sci. 63:2682–2690, 2016). Under abnormal working conditions, these actuators might not be functioning correctly as they should under normal working conditions. For instance, the main steam valve can be used to regulate the pressure of the main steam under reactor full power (RFP) working conditions. But the main steam valve must be closed under the turbine trip incident (or incidents that might lead to turbine trip) to prevent the steam from blowing on the blades of the turbine without connection between the turbine and the generator, making it unavailable for controlling the pressure of the main steam. Thus, research on the control strategies under abnormal working conditions is critical. The diverse operational scenarios of mHTGR incorporated with different industrial processes are also considered, bringing complexity to the control strategies while catering to a range of industrial requirements. Different control strategies under diverse abnormal working conditions are proposed in the case of diverse operational scenarios, and they can be utilized in the implementation and provide guidance for engineers. Nuclear safety must be, undoubtedly, preserved in these strategies by constraining the parameters of the steam and mHTGR without violating the safety setpoint of emergent opening of the safety valves and causing unexpected power surge on the reactors. By adhering to these principles, the proposed control strategies aim to maintain the integrity and safe operation of mHTGR-based nuclear power plant under all conditions.