Improved LADRC-based control strategy for fast transient response of FSBB converters

Abstract

Four-switch buck-boost (FSBB) converters are attractive for non-isolated dc-dc conversion over a wide input-voltage range, but conventional voltage-loop designs often suffer from slow recovery, overshoot, and difficult parameter tuning under reference and load transients. Conventional linear active disturbance rejection control (LADRC) improves robustness, whereas its single-stage linear extended state observer (LESO) is limited by the tradeoff between disturbance-estimation speed and high-frequency noise amplification. This paper replaces the LESO with a cascaded linear extended state observer (CLESO). The front-stage observer estimates the dominant disturbance, and the rear-stage observer compensates the residual disturbance. Prototype experiments show that the proposed improved LADRC (ILADRC) shortens settling time and reduces voltage fluctuation under outputvoltage switching and load-step conditions. Representative tests show about 45% faster dynamic response than PI control.