Enhanced SMC Using ESO in Energy Storage Conversion Systems

On the issue of inrush current during grid-connected/islanded mode transitions in energy storage converters. this paper proposes an improved sliding mode control (SMC) algorithm based on an Extended State Observer (ESO). Building upon a parallel operation structure utilizing both PQ control and Virtual Synchronous Generator (VSG) control with a shared inner current loop, the inner current loop controller is modified to employ the improved SMC with ESO. Firstly, an ESO is designed to perform real-time online observation and estimation of the output variables—namely the d-axis and q-axis currents ($i_{d}, i_{q}$)—along with various system disturbances. Subsequently, based on the obtained estimations, an improved SMC algorithm is utilized to design the system controller.Finally, simulation results demonstrate that, compared to conventional PI control and traditional SMC, the proposed method achieves significantly smaller current surges during mode transitions.