Fractional-order sliding mode coordinated controller using super-twisting disturbance observer for an NSSS with...

Area of Science:

• Nuclear Engineering
• Control Systems Theory
• Applied Mathematics

Background:

• Nuclear steam supply systems (NSSS) require robust control for safe and efficient operation.
• Complex operating conditions and disturbances challenge existing control strategies.
• Enhancing stability, reliability, and performance under uncertainty is critical.

Purpose of the Study:

• To develop an advanced fractional-order sliding mode coordinated control (FOSMCC) strategy.
• To integrate dual super-twisting disturbance observers (STDOs) for superior disturbance rejection.
• To guarantee predefined-time stability for the NSSS under compound disturbances.

Main Methods:

• Synthesis of fractional-order control, predefined-time theory, and sliding mode control.
• Implementation of a disturbance feedforward compensation loop driven by dual STDOs.
• Theoretical stability analysis using Lyapunov's direct approach.

Main Results:

• The FOSMCC strategy ensures fast transient response, high steady-state precision, and robust disturbance rejection.
• Theoretical demonstration of superior predefined-time stability for the NSSS.
• Significant reduction in integral absolute control error for nuclear power (89.37%) and water level (87.67%) compared to FOFTSMC, and even greater reductions compared to PACC (99.97% and 99.99%).

Conclusions:

• The proposed FOSMCC strategy with STDOs significantly outperforms existing controllers (FOFTSMC, PACC).
• The strategy offers enhanced control performance, stability, and reliability for NSSS.
• Validated effectiveness in mitigating complex, time-varying operating conditions and compound disturbances.