Research on a precise control system for hydrogen blending ratios in natural gas pipelines

Objective Hydrogen-blended natural gas pipeline transportation offers an important means for the efficient and economical delivery of hydrogen energy. The precision in controlling hydrogen blending ratios ensures stability for downstream hydrogen utilization, thereby supporting the advancement of the “Hydrogen into Homes” project.

Methods To achieve this, a mathematical model was established using a system identification method, and a Smith-Fuzzy PID controller was constructed by integrating Smith predictive compensation, fuzzy control rules, intelligent control, and Proportional Integral Differential (PID) technology. Building on this foundation, a precise control system for hydrogen blending ratios in natural gas pipelines based on fuzzy PID control was developed. By adjusting the parameters of the Smith predictor, the system’s lag effect is estimated to correct deviations caused by lagging processes, enabling faster response to changes in control inputs by compensating for these processes, thereby improving the response speed and stability of the hydrogen blending ratio control system. Additionally, the fuzzy control strategy reduces computational load by fuzzifying data, allowing for the rapid generation of optimal parameter combinations and further enhancing the system’s responsiveness and stability. Simulink simulation technology was employed to obtain the proportional coefficient (K_P), integral coefficient (K_I), and differential coefficient (K_D) through empirical tuning. Subsequent comparative analyses revealed variations in parameters such as settling time, response time, and overshoot under traditional PID control, Smith-PID control, and Smith-Fuzzy PID control. Experiments with hydrogen blending ratios of 5％, 10％, 15％, and 20％ were performed on a precision control platform for hydrogen blending ratios in natural gas pipelines to validate the system’s control accuracy.

Results The results demonstrate improvements under the Smith-Fuzzy PID control by 79.9％, 70％, and 82.5％ in terms of settling time, response time, and overshoot, respectively, compared to traditional PID control, and by 44％, 50％, and 77.9％ compared to Smith-PID control. The average hydrogen blending accuracy under Smith-Fuzzy PID control remained within ±1.5％ across various hydrogen blending ratios.

Conclusion The precise hydrogen blending ratio control system based on Smith-Fuzzy PID control is suitable for complex nonlinear and lagging conditions including natural gas hydrogen blending. It effectively meets the requirements for the hydrogen blending ratio control of natural gas pipelines, including rapid response, stable output, and precise control. The research findings provide technical support for ensuring the safe pipeline transportation of hydrogen-blended natural gas and its safe utilization at terminals.