Adaptive Hybrid Excitation Control Strategy for Longitudinal–Transverse Excited Synchronous Generators to Improve Dynamic Stability

The increasing integration of renewable energy sources, distributed generation, and smart grid technologies has significantly increased the dynamic complexity of modern electric power systems. Under such operating conditions, synchronous generators are required to maintain stable voltage, enhance transient performance, and suppress electromechanical oscillations despite continuous variations in load demand and network disturbances. Conventional excitation control systems based on proportional–integral (PI) and proportional–integral–derivative (PID) regulators exhibit limited adaptability to nonlinear operating conditions because of their fixed controller parameters and simplified control structures. Consequently, developing advanced excitation control strategies capable of improving the dynamic stability and operational reliability of synchronous generators has become an important research challenge. This paper proposes an Adaptive Hybrid Excitation Control (AHEC) strategy for longitudinal–transverse excited synchronous generators to improve dynamic stability under variable operating conditions. The proposed approach integrates coordinated longitudinal and transverse excitation control with adaptive parameter tuning and nonlinear feedback compensation into a unified control framework. A comprehensive nonlinear mathematical model of the generator is developed in the synchronous dq-reference frame by considering stator electrical dynamics, dual excitation winding dynamics, electromagnetic cross-coupling, magnetic saturation, and rotor mechanical motion. Based on the developed model, an adaptive hybrid excitation controller is synthesized to coordinate excitation currents in real time, ensuring optimal magnetic flux distribution, enhanced damping characteristics, and improved transient performance. The effectiveness of the proposed control strategy is evaluated through detailed MATLAB/Simulink simulations under various operating scenarios, including sudden load changes, voltage sags, reactive power fluctuations, parameter uncertainties, and three-phase short-circuit faults. The obtained results are compared with those of conventional Automatic Voltage Regulator (AVR), PI, PID, and Adaptive PID excitation controllers using key dynamic performance indicators such as voltage overshoot, settling time, steady-state error, damping ratio, rotor-angle deviation, and transient stability margin. Simulation results demonstrate that the proposed Adaptive Hybrid Excitation Control strategy substantially improves voltage regulation accuracy, suppresses electromechanical oscillations, accelerates transient recovery, and enhances the overall dynamic stability of the longitudinal–transverse excited synchronous generator. Compared with conventional excitation control methods, the proposed controller provides superior robustness against nonlinear disturbances and parameter variations while maintaining stable operation over a wide range of operating conditions. The proposed methodology offers an effective solution for next-generation synchronous generators employed in renewable energy systems, autonomous micro grids, and intelligent power networks.