Grid-Connected Inverter Sliding Mode Control for Transient Stability

The patent transforms the current control problem from a linear PI controller with fixed parameters to a sliding mode controller where the control parameters (switching function, sliding surface) change dynamically based on system state. This allows the controller to adapt to different operating conditions and external disturbances, achieving consistent dynamic performance across the entire operating range while maintaining reasonable structural complexity through the use of standard sliding mode control framework.

The patent changes the Lyapunov function parameters by incorporating the sliding mode control variables and system state variables in a unified manner. This allows the Lyapunov function to accurately capture the nonlinear dynamics while maintaining a consistent calculation process. The transformed parameters enable the Lyapunov function to handle various operating conditions and external disturbances uniformly, reducing calculation complexity and improving consistency.

Instead of using a current controller limiter that clamps the control signal (which distorts the phase-locked loop dynamics), the patent inverts the approach by using a sliding mode controller that actively manages the nonlinearity through switching functions. The sliding mode controller prevents the need for limiters by ensuring the system state reaches and maintains the desired sliding surface, thereby preserving phase-locked loop dynamics while achieving the desired control range and transient stability.