Improved ADRC Current Low-Frequency Ripple Suppression Strategy Based on VFNF

In the two-stage inverter system, due to the space vector modulation (SVM), the midpoint potential of active neutral point clamped three-level inverter system (ANPC-TLIS) will have triple frequency fluctuation, under the influence of the closed-loop control strategy, the fluctuation amplitude of the lithium battery energy storage system (LBESS) output current will increase. To reduce the low-frequency output current fluctuation, a voltage loop strategy based on active disturbance rejection control (ADRC) with notch filter (NF)is proposed in this paper. In this scheme, the voltage outer-loop control strategy not only maintains voltage stability, but also reduces the fluctuation amplitude of reference current. In addition, during the electromagnetic transient process, the LBESS output current fluctuation frequency is constantly changing because the power supply frequency required by linear motor is constantly changing. To solve this problem, the inverter output current frequency is feedforward to the LBESS controller, forming a variable frequency notch filter (VFNF). Finally, the effectiveness of the proposed strategy is verified by fixed-frequency and variable frequency conditions experiments on RT-LAB experimental platform. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.