Dynamic modeling and electro-thermal complementarity mechanism of nuclear cogeneration system coupling pressurized water reactor & high-temperature gas-cooled reactor

With the rapid increase in renewable energy penetration, power grids face growing demands for flexible resources. Traditional nuclear power plants, limited by insufficient peak-shaving capability, struggle to meet flexibility requirements in high-renewable-penetration scenarios. This study develops and validates a nuclear cogeneration system model coupling pressurized water reactor and high-temperature gas-cooled reactor using Modelica language, proposes a coordinated control strategy for reactor-thermal-electric interactions. Dynamic characteristics under three typical operational modes—electric power regulation, thermal-power regulation, and thermo-electric coordination regulation—are simulated and analyzed. Comparative results demonstrate that the system exhibits multi-timescale coupled responses, with regulation times increasing in the order of electromechanical, pressure, and reactor dynamics. Despite the slow reactor response, fast and stable electric power regulation is achievable due to the buffering effect of the intermediate heating circuit on main steam pressure. Thermal power regulation exhibits weaker stability guarantees than electric power regulation. Under thermal-power regulation scenario, reactor power fluctuations peak over 160 MW (4.5 %Pe), while electric power and main steam pressure fluctuations are limited to 47 MW (3.9 %Pe) and 0.4 bar (0.6 %), respectively. In contrast, electric-power regulation scenario shows negligible state oscillations. The reactor-thermal-electric coordinated control strategy demonstrates strong electro-thermal complementarity: Reactor power variation and overshoot are reduced by 42 % and 55 %, respectively, while steam generator water level fluctuations decrease by 40 % (compared to electric-power regulation) and 64 % (compared to thermal-power regulation), significantly improving dynamic performance and stability during power regulation. This strategy provides a novel solution for nuclear power plants to support flexible grid operation in high-renewable-penetration scenarios.