Research on double closed-loop stability of NPC-type energy storage converters based on adaptive backstepping control

To address the issues of slow dynamic response and insufficient robustness in traditional PI control for neutral-point-clamped (NPC) energy storage converters, which are caused by strong nonlinearity, parameter perturbations, and current coupling, this paper proposes an adaptive backstepping double closed-loop control strategy. Firstly, a mathematical model of the NPC converter in the three-phase stationary coordinate system is established based on Kirchhoff's laws, and then transformed into the dq synchronous rotating coordinate system via Park transformation. Secondly, a double closed-loop structure consisting of a voltage outer loop and a current inner loop is designed: the voltage outer loop adopts PI control to generate current reference commands, while the current inner loop replaces the traditional PI with adaptive backstepping control. The control law is derived using the "subsystem decomposition" concept combined with the Lyapunov function, and an error-feedback adaptive law is introduced to real-time estimate perturbations of filter inductance and equivalent resistance, compensating for parameter uncertainties. Finally, a simulation model is built in MATLAB/Simulink, and verification is conducted under charge-discharge switching and grid phase jump conditions. The results show that the strategy can achieve smooth charge-discharge mode switching, effectively suppress grid phase disturbances, improve dynamic response, and significantly optimize robustness and power quality, meeting the high-precision control requirements of new power systems for NPC energy storage converters.