Enhanced Voltage Response of SMES-DVR via Sliding Mode Control With Extended State Observer

A DVR based on superconducting magnet energy storage (SMES-DVR) could offer higher power in milliseconds to compensate for the voltage disturbance. However, nonlinearities and load disturbances of SMES-DVR usually induce voltage fluctuations on DC-link, which reduces the accuracy and response performance. A novel composite control strategy based on high-order sliding mode control with extended state observer (ESO-HOSMC) is proposed to address the critical challenge of DC-link voltage fluctuations in SMES-DVR. By synergizing extended state observer-based disturbance estimation with super-twisting high-order sliding mode control, ESO-HOSMC control method effectively balances the contradiction between rapid response and operational stability during the charging and discharging process of the superconducting magnet, while reducing total harmonic distortion of sensitive load voltage. Theoretical analysis containing controller modeling, designing and stability analysis has been demonstrated. In addition, performances among the ESO-HOSMC control, model predictive control (MPC) and conventional PI control of SMES-DVR have been compared under different voltage sag or swell scenarios. The results show that the proposed control scheme effectively elevates compensation performance and the stability of DC bus voltage for SMES-DVR.